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[PATCH v2 4/8] drm/fb-helper: Add fb_deferred_io support

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  [PATCH v2 4/8] drm/fb-helper: Add fb_deferred_io support Noralf Trønnes <noralf@tronnes.org> - 2016-04-24 23:00 +0200
    Re: [PATCH v2 4/8] drm/fb-helper: Add fb_deferred_io support Daniel Vetter <daniel@ffwll.ch> - 2016-04-25 11:20 +0200
      Re: [PATCH v2 4/8] drm/fb-helper: Add fb_deferred_io support Noralf Trønnes <noralf@tronnes.org> - 2016-04-26 18:30 +0200
        Re: [PATCH v2 4/8] drm/fb-helper: Add fb_deferred_io support Daniel Vetter <daniel@ffwll.ch> - 2016-04-26 19:20 +0200
          Re: [PATCH v2 4/8] drm/fb-helper: Add fb_deferred_io support Noralf Trønnes <noralf@tronnes.org> - 2016-04-27 11:50 +0200
            Re: [PATCH v2 4/8] drm/fb-helper: Add fb_deferred_io support Daniel Vetter <daniel@ffwll.ch> - 2016-04-27 13:20 +0200

#1385908 — [PATCH v2 4/8] drm/fb-helper: Add fb_deferred_io support

This adds deferred io support if CONFIG_FB_DEFERRED_IO is enabled.
The fbdev framebuffer changes are flushed using the callback
(struct drm_framebuffer *)->funcs->dirty() by a dedicated worker
ensuring that it always runs in process context.

Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
---

Changes since v1:
- Use a dedicated worker to run the framebuffer flushing like qxl does
- Add parameter descriptions to drm_fb_helper_deferred_io

 drivers/gpu/drm/drm_fb_helper.c | 127 +++++++++++++++++++++++++++++++++++++++-
 include/drm/drm_fb_helper.h     |  17 ++++++
 2 files changed, 143 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index 855108e..46ee6f8 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -40,6 +40,7 @@
 #include <drm/drm_crtc_helper.h>
 #include <drm/drm_atomic.h>
 #include <drm/drm_atomic_helper.h>
+#include <drm/drm_rect.h>

 static bool drm_fbdev_emulation = true;
 module_param_named(fbdev_emulation, drm_fbdev_emulation, bool, 0600);
@@ -48,6 +49,10 @@ MODULE_PARM_DESC(fbdev_emulation,

 static LIST_HEAD(kernel_fb_helper_list);

+static void drm_fb_helper_dirty_init(struct drm_fb_helper *helper);
+static void drm_fb_helper_dirty(struct fb_info *info, u32 x, u32 y,
+				u32 width, u32 height);
+
 /**
  * DOC: fbdev helpers
  *
@@ -84,6 +89,16 @@ static LIST_HEAD(kernel_fb_helper_list);
  * and set up an initial configuration using the detected hardware, drivers
  * should call drm_fb_helper_single_add_all_connectors() followed by
  * drm_fb_helper_initial_config().
+ *
+ * If CONFIG_FB_DEFERRED_IO is enabled and
+ * (struct drm_framebuffer *)->funcs->dirty is set, the
+ * drm_fb_helper_{cfb,sys}_{write,fillrect,copyarea,imageblit} functions
+ * will accumulate changes and schedule (struct fb_helper).dirty_work to run
+ * right away. This worker then calls the dirty() function ensuring that it
+ * will always run in process context since the fb_*() function could be
+ * running in atomic context. If drm_fb_helper_deferred_io() is used as the
+ * deferred_io callback it will also schedule dirty_work with the damage
+ * collected from the mmap page writes.
  */

 /**
@@ -401,11 +416,14 @@ backoff:
 static int restore_fbdev_mode(struct drm_fb_helper *fb_helper)
 {
 	struct drm_device *dev = fb_helper->dev;
+	struct fb_info *info = fb_helper->fbdev;
 	struct drm_plane *plane;
 	int i;

 	drm_warn_on_modeset_not_all_locked(dev);

+	drm_fb_helper_dirty(info, 0, 0, info->var.xres, info->var.yres);
+
 	if (fb_helper->atomic)
 		return restore_fbdev_mode_atomic(fb_helper);

@@ -650,6 +668,7 @@ void drm_fb_helper_prepare(struct drm_device *dev, struct drm_fb_helper *helper,
 			   const struct drm_fb_helper_funcs *funcs)
 {
 	INIT_LIST_HEAD(&helper->kernel_fb_list);
+	drm_fb_helper_dirty_init(helper);
 	helper->funcs = funcs;
 	helper->dev = dev;
 }
@@ -834,6 +853,93 @@ void drm_fb_helper_unlink_fbi(struct drm_fb_helper *fb_helper)
 }
 EXPORT_SYMBOL(drm_fb_helper_unlink_fbi);

+#ifdef CONFIG_FB_DEFERRED_IO
+static void drm_fb_helper_dirty_work(struct work_struct *work)
+{
+	struct drm_fb_helper *helper = container_of(work, struct drm_fb_helper,
+						    dirty_work);
+	struct drm_clip_rect clip;
+	unsigned long flags;
+
+	spin_lock_irqsave(&helper->dirty_lock, flags);
+	clip = helper->dirty_clip;
+	drm_clip_rect_reset(&helper->dirty_clip);
+	spin_unlock_irqrestore(&helper->dirty_lock, flags);
+
+	helper->fb->funcs->dirty(helper->fb, NULL, 0, 0, &clip, 1);
+}
+
+static void drm_fb_helper_dirty_init(struct drm_fb_helper *helper)
+{
+	spin_lock_init(&helper->dirty_lock);
+	INIT_WORK(&helper->dirty_work, drm_fb_helper_dirty_work);
+}
+
+static void drm_fb_helper_dirty(struct fb_info *info, u32 x, u32 y,
+				u32 width, u32 height)
+{
+	struct drm_fb_helper *helper = info->par;
+	struct drm_clip_rect clip;
+	unsigned long flags;
+
+	if (!helper->fb->funcs->dirty)
+		return;
+
+	clip.x1 = x;
+	clip.x2 = x + width;
+	clip.y1 = y;
+	clip.y2 = y + height;
+
+	spin_lock_irqsave(&helper->dirty_lock, flags);
+	drm_clip_rect_merge(&helper->dirty_clip, &clip, 1, 0, 0, 0);
+	spin_unlock_irqrestore(&helper->dirty_lock, flags);
+
+	schedule_work(&helper->dirty_work);
+}
+
+/**
+ * drm_fb_helper_deferred_io() - fbdev deferred_io callback function
+ * @info: fb_info struct pointer
+ * @pagelist: list of dirty mmap framebuffer pages
+ *
+ * This function is used as the (struct fb_deferred_io *)->deferred_io
+ * callback function for flushing the fbdev mmap writes.
+ */
+void drm_fb_helper_deferred_io(struct fb_info *info,
+			       struct list_head *pagelist)
+{
+	unsigned long start, end, min, max;
+	struct page *page;
+	u32 y1, y2;
+
+	min = ULONG_MAX;
+	max = 0;
+	list_for_each_entry(page, pagelist, lru) {
+		start = page->index << PAGE_SHIFT;
+		end = start + PAGE_SIZE - 1;
+		min = min(min, start);
+		max = max(max, end);
+	}
+
+	if (min < max) {
+		y1 = min / info->fix.line_length;
+		y2 = min_t(u32, max / info->fix.line_length, info->var.yres);
+		drm_fb_helper_dirty(info, 0, y1, info->var.xres, y2 - y1);
+	}
+}
+EXPORT_SYMBOL(drm_fb_helper_deferred_io);
+
+#else
+static void drm_fb_helper_dirty_init(struct drm_fb_helper *helper)
+{
+}
+
+static void drm_fb_helper_dirty(struct fb_info *info, u32 x, u32 y,
+				u32 width, u32 height)
+{
+}
+#endif /* CONFIG_FB_DEFERRED_IO */
+
 /**
  * drm_fb_helper_sys_read - wrapper around fb_sys_read
  * @info: fb_info struct pointer
@@ -862,7 +968,14 @@ EXPORT_SYMBOL(drm_fb_helper_sys_read);
 ssize_t drm_fb_helper_sys_write(struct fb_info *info, const char __user *buf,
 				size_t count, loff_t *ppos)
 {
-	return fb_sys_write(info, buf, count, ppos);
+	ssize_t ret;
+
+	ret = fb_sys_write(info, buf, count, ppos);
+	if (ret > 0)
+		drm_fb_helper_dirty(info, 0, 0, info->var.xres,
+				    info->var.yres);
+
+	return ret;
 }
 EXPORT_SYMBOL(drm_fb_helper_sys_write);

@@ -877,6 +990,8 @@ void drm_fb_helper_sys_fillrect(struct fb_info *info,
 				const struct fb_fillrect *rect)
 {
 	sys_fillrect(info, rect);
+	drm_fb_helper_dirty(info, rect->dx, rect->dy,
+			    rect->width, rect->height);
 }
 EXPORT_SYMBOL(drm_fb_helper_sys_fillrect);

@@ -891,6 +1006,8 @@ void drm_fb_helper_sys_copyarea(struct fb_info *info,
 				const struct fb_copyarea *area)
 {
 	sys_copyarea(info, area);
+	drm_fb_helper_dirty(info, area->dx, area->dy,
+			    area->width, area->height);
 }
 EXPORT_SYMBOL(drm_fb_helper_sys_copyarea);

@@ -905,6 +1022,8 @@ void drm_fb_helper_sys_imageblit(struct fb_info *info,
 				 const struct fb_image *image)
 {
 	sys_imageblit(info, image);
+	drm_fb_helper_dirty(info, image->dx, image->dy,
+			    image->width, image->height);
 }
 EXPORT_SYMBOL(drm_fb_helper_sys_imageblit);

@@ -919,6 +1038,8 @@ void drm_fb_helper_cfb_fillrect(struct fb_info *info,
 				const struct fb_fillrect *rect)
 {
 	cfb_fillrect(info, rect);
+	drm_fb_helper_dirty(info, rect->dx, rect->dy,
+			    rect->width, rect->height);
 }
 EXPORT_SYMBOL(drm_fb_helper_cfb_fillrect);

@@ -933,6 +1054,8 @@ void drm_fb_helper_cfb_copyarea(struct fb_info *info,
 				const struct fb_copyarea *area)
 {
 	cfb_copyarea(info, area);
+	drm_fb_helper_dirty(info, area->dx, area->dy,
+			    area->width, area->height);
 }
 EXPORT_SYMBOL(drm_fb_helper_cfb_copyarea);

@@ -947,6 +1070,8 @@ void drm_fb_helper_cfb_imageblit(struct fb_info *info,
 				 const struct fb_image *image)
 {
 	cfb_imageblit(info, image);
+	drm_fb_helper_dirty(info, image->dx, image->dy,
+			    image->width, image->height);
 }
 EXPORT_SYMBOL(drm_fb_helper_cfb_imageblit);

diff --git a/include/drm/drm_fb_helper.h b/include/drm/drm_fb_helper.h
index 062723b..dde825c 100644
--- a/include/drm/drm_fb_helper.h
+++ b/include/drm/drm_fb_helper.h
@@ -172,6 +172,10 @@ struct drm_fb_helper_connector {
  * @funcs: driver callbacks for fb helper
  * @fbdev: emulated fbdev device info struct
  * @pseudo_palette: fake palette of 16 colors
+ * @dirty_clip: clip rectangle used with deferred_io to accumulate damage to
+ *              the screen buffer
+ * @dirty_lock: spinlock protecting @dirty_clip
+ * @dirty_work: worker used to flush the framebuffer
  *
  * This is the main structure used by the fbdev helpers. Drivers supporting
  * fbdev emulation should embedded this into their overall driver structure.
@@ -189,6 +193,11 @@ struct drm_fb_helper {
 	const struct drm_fb_helper_funcs *funcs;
 	struct fb_info *fbdev;
 	u32 pseudo_palette[17];
+#ifdef CONFIG_FB_DEFERRED_IO
+	struct drm_clip_rect dirty_clip;
+	spinlock_t dirty_lock;
+	struct work_struct dirty_work;
+#endif

 	/**
 	 * @kernel_fb_list:
@@ -245,6 +254,9 @@ void drm_fb_helper_fill_fix(struct fb_info *info, uint32_t pitch,

 void drm_fb_helper_unlink_fbi(struct drm_fb_helper *fb_helper);

+void drm_fb_helper_deferred_io(struct fb_info *info,
+			       struct list_head *pagelist);
+
 ssize_t drm_fb_helper_sys_read(struct fb_info *info, char __user *buf,
 			       size_t count, loff_t *ppos);
 ssize_t drm_fb_helper_sys_write(struct fb_info *info, const char __user *buf,
@@ -368,6 +380,11 @@ static inline void drm_fb_helper_unlink_fbi(struct drm_fb_helper *fb_helper)
 {
 }

+static inline void drm_fb_helper_deferred_io(struct fb_info *info,
+					     struct list_head *pagelist)
+{
+}
+
 static inline ssize_t drm_fb_helper_sys_read(struct fb_info *info,
 					     char __user *buf, size_t count,
 					     loff_t *ppos)
--
2.2.2

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#1386157

On Sun, Apr 24, 2016 at 10:48:58PM +0200, Noralf Trønnes wrote:
> This adds deferred io support if CONFIG_FB_DEFERRED_IO is enabled.
> The fbdev framebuffer changes are flushed using the callback
> (struct drm_framebuffer *)->funcs->dirty() by a dedicated worker
> ensuring that it always runs in process context.
> 
> Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
> ---
> 
> Changes since v1:
> - Use a dedicated worker to run the framebuffer flushing like qxl does
> - Add parameter descriptions to drm_fb_helper_deferred_io
> 
>  drivers/gpu/drm/drm_fb_helper.c | 127 +++++++++++++++++++++++++++++++++++++++-
>  include/drm/drm_fb_helper.h     |  17 ++++++
>  2 files changed, 143 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> index 855108e..46ee6f8 100644
> --- a/drivers/gpu/drm/drm_fb_helper.c
> +++ b/drivers/gpu/drm/drm_fb_helper.c
> @@ -40,6 +40,7 @@
>  #include <drm/drm_crtc_helper.h>
>  #include <drm/drm_atomic.h>
>  #include <drm/drm_atomic_helper.h>
> +#include <drm/drm_rect.h>
> 
>  static bool drm_fbdev_emulation = true;
>  module_param_named(fbdev_emulation, drm_fbdev_emulation, bool, 0600);
> @@ -48,6 +49,10 @@ MODULE_PARM_DESC(fbdev_emulation,
> 
>  static LIST_HEAD(kernel_fb_helper_list);
> 
> +static void drm_fb_helper_dirty_init(struct drm_fb_helper *helper);
> +static void drm_fb_helper_dirty(struct fb_info *info, u32 x, u32 y,
> +				u32 width, u32 height);
> +
>  /**
>   * DOC: fbdev helpers
>   *
> @@ -84,6 +89,16 @@ static LIST_HEAD(kernel_fb_helper_list);
>   * and set up an initial configuration using the detected hardware, drivers
>   * should call drm_fb_helper_single_add_all_connectors() followed by
>   * drm_fb_helper_initial_config().
> + *
> + * If CONFIG_FB_DEFERRED_IO is enabled and
> + * (struct drm_framebuffer *)->funcs->dirty is set, the
> + * drm_fb_helper_{cfb,sys}_{write,fillrect,copyarea,imageblit} functions
> + * will accumulate changes and schedule (struct fb_helper).dirty_work to run
> + * right away. This worker then calls the dirty() function ensuring that it
> + * will always run in process context since the fb_*() function could be
> + * running in atomic context. If drm_fb_helper_deferred_io() is used as the
> + * deferred_io callback it will also schedule dirty_work with the damage
> + * collected from the mmap page writes.

One thing to consider (and personally I don't care either way) is whether
we shouldn't just select CONFIG_FB_DEFERRED_IO if the fbdev helpers are
enabled. Pushing that out to drivers is imo a bit fragile.

But like I said I'm ok with either way.

>   */
> 
>  /**
> @@ -401,11 +416,14 @@ backoff:
>  static int restore_fbdev_mode(struct drm_fb_helper *fb_helper)
>  {
>  	struct drm_device *dev = fb_helper->dev;
> +	struct fb_info *info = fb_helper->fbdev;
>  	struct drm_plane *plane;
>  	int i;
> 
>  	drm_warn_on_modeset_not_all_locked(dev);
> 
> +	drm_fb_helper_dirty(info, 0, 0, info->var.xres, info->var.yres);

Why is this needed? If you do a modeset (or pageflip or whatever) drivers
are supposed to re-upload the entire screen. We've talked about adding a
dirty rectangle to atomic to allow userspace to optimize this, but there
should _never_ be a need to do a dirtyfb call around a modeset. Probably
just a driver bug in your panel drm drivers?

With the above line removed:

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

> +
>  	if (fb_helper->atomic)
>  		return restore_fbdev_mode_atomic(fb_helper);
> 
> @@ -650,6 +668,7 @@ void drm_fb_helper_prepare(struct drm_device *dev, struct drm_fb_helper *helper,
>  			   const struct drm_fb_helper_funcs *funcs)
>  {
>  	INIT_LIST_HEAD(&helper->kernel_fb_list);
> +	drm_fb_helper_dirty_init(helper);
>  	helper->funcs = funcs;
>  	helper->dev = dev;
>  }
> @@ -834,6 +853,93 @@ void drm_fb_helper_unlink_fbi(struct drm_fb_helper *fb_helper)
>  }
>  EXPORT_SYMBOL(drm_fb_helper_unlink_fbi);
> 
> +#ifdef CONFIG_FB_DEFERRED_IO
> +static void drm_fb_helper_dirty_work(struct work_struct *work)
> +{
> +	struct drm_fb_helper *helper = container_of(work, struct drm_fb_helper,
> +						    dirty_work);
> +	struct drm_clip_rect clip;
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&helper->dirty_lock, flags);
> +	clip = helper->dirty_clip;
> +	drm_clip_rect_reset(&helper->dirty_clip);
> +	spin_unlock_irqrestore(&helper->dirty_lock, flags);
> +
> +	helper->fb->funcs->dirty(helper->fb, NULL, 0, 0, &clip, 1);
> +}
> +
> +static void drm_fb_helper_dirty_init(struct drm_fb_helper *helper)
> +{
> +	spin_lock_init(&helper->dirty_lock);
> +	INIT_WORK(&helper->dirty_work, drm_fb_helper_dirty_work);
> +}
> +
> +static void drm_fb_helper_dirty(struct fb_info *info, u32 x, u32 y,
> +				u32 width, u32 height)
> +{
> +	struct drm_fb_helper *helper = info->par;
> +	struct drm_clip_rect clip;
> +	unsigned long flags;
> +
> +	if (!helper->fb->funcs->dirty)
> +		return;
> +
> +	clip.x1 = x;
> +	clip.x2 = x + width;
> +	clip.y1 = y;
> +	clip.y2 = y + height;
> +
> +	spin_lock_irqsave(&helper->dirty_lock, flags);
> +	drm_clip_rect_merge(&helper->dirty_clip, &clip, 1, 0, 0, 0);
> +	spin_unlock_irqrestore(&helper->dirty_lock, flags);
> +
> +	schedule_work(&helper->dirty_work);
> +}
> +
> +/**
> + * drm_fb_helper_deferred_io() - fbdev deferred_io callback function
> + * @info: fb_info struct pointer
> + * @pagelist: list of dirty mmap framebuffer pages
> + *
> + * This function is used as the (struct fb_deferred_io *)->deferred_io
> + * callback function for flushing the fbdev mmap writes.
> + */
> +void drm_fb_helper_deferred_io(struct fb_info *info,
> +			       struct list_head *pagelist)
> +{
> +	unsigned long start, end, min, max;
> +	struct page *page;
> +	u32 y1, y2;
> +
> +	min = ULONG_MAX;
> +	max = 0;
> +	list_for_each_entry(page, pagelist, lru) {
> +		start = page->index << PAGE_SHIFT;
> +		end = start + PAGE_SIZE - 1;
> +		min = min(min, start);
> +		max = max(max, end);
> +	}
> +
> +	if (min < max) {
> +		y1 = min / info->fix.line_length;
> +		y2 = min_t(u32, max / info->fix.line_length, info->var.yres);
> +		drm_fb_helper_dirty(info, 0, y1, info->var.xres, y2 - y1);
> +	}
> +}
> +EXPORT_SYMBOL(drm_fb_helper_deferred_io);
> +
> +#else
> +static void drm_fb_helper_dirty_init(struct drm_fb_helper *helper)
> +{
> +}
> +
> +static void drm_fb_helper_dirty(struct fb_info *info, u32 x, u32 y,
> +				u32 width, u32 height)
> +{
> +}
> +#endif /* CONFIG_FB_DEFERRED_IO */
> +
>  /**
>   * drm_fb_helper_sys_read - wrapper around fb_sys_read
>   * @info: fb_info struct pointer
> @@ -862,7 +968,14 @@ EXPORT_SYMBOL(drm_fb_helper_sys_read);
>  ssize_t drm_fb_helper_sys_write(struct fb_info *info, const char __user *buf,
>  				size_t count, loff_t *ppos)
>  {
> -	return fb_sys_write(info, buf, count, ppos);
> +	ssize_t ret;
> +
> +	ret = fb_sys_write(info, buf, count, ppos);
> +	if (ret > 0)
> +		drm_fb_helper_dirty(info, 0, 0, info->var.xres,
> +				    info->var.yres);
> +
> +	return ret;
>  }
>  EXPORT_SYMBOL(drm_fb_helper_sys_write);
> 
> @@ -877,6 +990,8 @@ void drm_fb_helper_sys_fillrect(struct fb_info *info,
>  				const struct fb_fillrect *rect)
>  {
>  	sys_fillrect(info, rect);
> +	drm_fb_helper_dirty(info, rect->dx, rect->dy,
> +			    rect->width, rect->height);
>  }
>  EXPORT_SYMBOL(drm_fb_helper_sys_fillrect);
> 
> @@ -891,6 +1006,8 @@ void drm_fb_helper_sys_copyarea(struct fb_info *info,
>  				const struct fb_copyarea *area)
>  {
>  	sys_copyarea(info, area);
> +	drm_fb_helper_dirty(info, area->dx, area->dy,
> +			    area->width, area->height);
>  }
>  EXPORT_SYMBOL(drm_fb_helper_sys_copyarea);
> 
> @@ -905,6 +1022,8 @@ void drm_fb_helper_sys_imageblit(struct fb_info *info,
>  				 const struct fb_image *image)
>  {
>  	sys_imageblit(info, image);
> +	drm_fb_helper_dirty(info, image->dx, image->dy,
> +			    image->width, image->height);
>  }
>  EXPORT_SYMBOL(drm_fb_helper_sys_imageblit);
> 
> @@ -919,6 +1038,8 @@ void drm_fb_helper_cfb_fillrect(struct fb_info *info,
>  				const struct fb_fillrect *rect)
>  {
>  	cfb_fillrect(info, rect);
> +	drm_fb_helper_dirty(info, rect->dx, rect->dy,
> +			    rect->width, rect->height);
>  }
>  EXPORT_SYMBOL(drm_fb_helper_cfb_fillrect);
> 
> @@ -933,6 +1054,8 @@ void drm_fb_helper_cfb_copyarea(struct fb_info *info,
>  				const struct fb_copyarea *area)
>  {
>  	cfb_copyarea(info, area);
> +	drm_fb_helper_dirty(info, area->dx, area->dy,
> +			    area->width, area->height);
>  }
>  EXPORT_SYMBOL(drm_fb_helper_cfb_copyarea);
> 
> @@ -947,6 +1070,8 @@ void drm_fb_helper_cfb_imageblit(struct fb_info *info,
>  				 const struct fb_image *image)
>  {
>  	cfb_imageblit(info, image);
> +	drm_fb_helper_dirty(info, image->dx, image->dy,
> +			    image->width, image->height);
>  }
>  EXPORT_SYMBOL(drm_fb_helper_cfb_imageblit);
> 
> diff --git a/include/drm/drm_fb_helper.h b/include/drm/drm_fb_helper.h
> index 062723b..dde825c 100644
> --- a/include/drm/drm_fb_helper.h
> +++ b/include/drm/drm_fb_helper.h
> @@ -172,6 +172,10 @@ struct drm_fb_helper_connector {
>   * @funcs: driver callbacks for fb helper
>   * @fbdev: emulated fbdev device info struct
>   * @pseudo_palette: fake palette of 16 colors
> + * @dirty_clip: clip rectangle used with deferred_io to accumulate damage to
> + *              the screen buffer
> + * @dirty_lock: spinlock protecting @dirty_clip
> + * @dirty_work: worker used to flush the framebuffer
>   *
>   * This is the main structure used by the fbdev helpers. Drivers supporting
>   * fbdev emulation should embedded this into their overall driver structure.
> @@ -189,6 +193,11 @@ struct drm_fb_helper {
>  	const struct drm_fb_helper_funcs *funcs;
>  	struct fb_info *fbdev;
>  	u32 pseudo_palette[17];
> +#ifdef CONFIG_FB_DEFERRED_IO
> +	struct drm_clip_rect dirty_clip;
> +	spinlock_t dirty_lock;
> +	struct work_struct dirty_work;
> +#endif
> 
>  	/**
>  	 * @kernel_fb_list:
> @@ -245,6 +254,9 @@ void drm_fb_helper_fill_fix(struct fb_info *info, uint32_t pitch,
> 
>  void drm_fb_helper_unlink_fbi(struct drm_fb_helper *fb_helper);
> 
> +void drm_fb_helper_deferred_io(struct fb_info *info,
> +			       struct list_head *pagelist);
> +
>  ssize_t drm_fb_helper_sys_read(struct fb_info *info, char __user *buf,
>  			       size_t count, loff_t *ppos);
>  ssize_t drm_fb_helper_sys_write(struct fb_info *info, const char __user *buf,
> @@ -368,6 +380,11 @@ static inline void drm_fb_helper_unlink_fbi(struct drm_fb_helper *fb_helper)
>  {
>  }
> 
> +static inline void drm_fb_helper_deferred_io(struct fb_info *info,
> +					     struct list_head *pagelist)
> +{
> +}
> +
>  static inline ssize_t drm_fb_helper_sys_read(struct fb_info *info,
>  					     char __user *buf, size_t count,
>  					     loff_t *ppos)
> --
> 2.2.2
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

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#1387678

Den 25.04.2016 11:09, skrev Daniel Vetter:
> On Sun, Apr 24, 2016 at 10:48:58PM +0200, Noralf Trønnes wrote:
>> This adds deferred io support if CONFIG_FB_DEFERRED_IO is enabled.
>> The fbdev framebuffer changes are flushed using the callback
>> (struct drm_framebuffer *)->funcs->dirty() by a dedicated worker
>> ensuring that it always runs in process context.
>>
>> Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
>> ---
>>
>> Changes since v1:
>> - Use a dedicated worker to run the framebuffer flushing like qxl does
>> - Add parameter descriptions to drm_fb_helper_deferred_io
>>
>>   drivers/gpu/drm/drm_fb_helper.c | 127 +++++++++++++++++++++++++++++++++++++++-
>>   include/drm/drm_fb_helper.h     |  17 ++++++
>>   2 files changed, 143 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
>> index 855108e..46ee6f8 100644
>> --- a/drivers/gpu/drm/drm_fb_helper.c
>> +++ b/drivers/gpu/drm/drm_fb_helper.c
>> @@ -40,6 +40,7 @@
>>   #include <drm/drm_crtc_helper.h>
>>   #include <drm/drm_atomic.h>
>>   #include <drm/drm_atomic_helper.h>
>> +#include <drm/drm_rect.h>
>>
>>   static bool drm_fbdev_emulation = true;
>>   module_param_named(fbdev_emulation, drm_fbdev_emulation, bool, 0600);
>> @@ -48,6 +49,10 @@ MODULE_PARM_DESC(fbdev_emulation,
>>
>>   static LIST_HEAD(kernel_fb_helper_list);
>>
>> +static void drm_fb_helper_dirty_init(struct drm_fb_helper *helper);
>> +static void drm_fb_helper_dirty(struct fb_info *info, u32 x, u32 y,
>> +				u32 width, u32 height);
>> +
>>   /**
>>    * DOC: fbdev helpers
>>    *
>> @@ -84,6 +89,16 @@ static LIST_HEAD(kernel_fb_helper_list);
>>    * and set up an initial configuration using the detected hardware, drivers
>>    * should call drm_fb_helper_single_add_all_connectors() followed by
>>    * drm_fb_helper_initial_config().
>> + *
>> + * If CONFIG_FB_DEFERRED_IO is enabled and
>> + * (struct drm_framebuffer *)->funcs->dirty is set, the
>> + * drm_fb_helper_{cfb,sys}_{write,fillrect,copyarea,imageblit} functions
>> + * will accumulate changes and schedule (struct fb_helper).dirty_work to run
>> + * right away. This worker then calls the dirty() function ensuring that it
>> + * will always run in process context since the fb_*() function could be
>> + * running in atomic context. If drm_fb_helper_deferred_io() is used as the
>> + * deferred_io callback it will also schedule dirty_work with the damage
>> + * collected from the mmap page writes.
> One thing to consider (and personally I don't care either way) is whether
> we shouldn't just select CONFIG_FB_DEFERRED_IO if the fbdev helpers are
> enabled. Pushing that out to drivers is imo a bit fragile.
>
> But like I said I'm ok with either way.

My concern was adding code and data that only a few drivers would
actually use. But of course there's the tradeoff with complexity.
I use this to enable it:
         select FB_DEFERRED_IO if DRM_KMS_FB_HELPER

I guess the maintainer has to make this choice between size and 
complexity :-)
I can enable it by default if you want, drm is both huge and complex so I
don't know what's best.

As a sidenote, I have also put all the fbdev code in a file of it's own to
make it simple with regards to the DRM_FBDEV_EMULATION user option:
tinydrm-$(CONFIG_DRM_KMS_FB_HELPER)     += tinydrm-fbdev.o

>>    */
>>
>>   /**
>> @@ -401,11 +416,14 @@ backoff:
>>   static int restore_fbdev_mode(struct drm_fb_helper *fb_helper)
>>   {
>>   	struct drm_device *dev = fb_helper->dev;
>> +	struct fb_info *info = fb_helper->fbdev;
>>   	struct drm_plane *plane;
>>   	int i;
>>
>>   	drm_warn_on_modeset_not_all_locked(dev);
>>
>> +	drm_fb_helper_dirty(info, 0, 0, info->var.xres, info->var.yres);
> Why is this needed? If you do a modeset (or pageflip or whatever) drivers
> are supposed to re-upload the entire screen. We've talked about adding a
> dirty rectangle to atomic to allow userspace to optimize this, but there
> should _never_ be a need to do a dirtyfb call around a modeset. Probably
> just a driver bug in your panel drm drivers?

Ok, in tinydrm I now set a flag in &drm_simple_display_pipe_funcs
->plane_update to indicate that the next dirty() should do the whole
framebuffer which seems to work fine.
Should I actually perform the update as well?
If so I would need to add a worker in tinydrm to do that.


Noralf.

> With the above line removed:
>
> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
>
>> +
>>   	if (fb_helper->atomic)
>>   		return restore_fbdev_mode_atomic(fb_helper);
>>
>> @@ -650,6 +668,7 @@ void drm_fb_helper_prepare(struct drm_device *dev, struct drm_fb_helper *helper,
>>   			   const struct drm_fb_helper_funcs *funcs)
>>   {
>>   	INIT_LIST_HEAD(&helper->kernel_fb_list);
>> +	drm_fb_helper_dirty_init(helper);
>>   	helper->funcs = funcs;
>>   	helper->dev = dev;
>>   }
>> @@ -834,6 +853,93 @@ void drm_fb_helper_unlink_fbi(struct drm_fb_helper *fb_helper)
>>   }
>>   EXPORT_SYMBOL(drm_fb_helper_unlink_fbi);
>>
>> +#ifdef CONFIG_FB_DEFERRED_IO
>> +static void drm_fb_helper_dirty_work(struct work_struct *work)
>> +{
>> +	struct drm_fb_helper *helper = container_of(work, struct drm_fb_helper,
>> +						    dirty_work);
>> +	struct drm_clip_rect clip;
>> +	unsigned long flags;
>> +
>> +	spin_lock_irqsave(&helper->dirty_lock, flags);
>> +	clip = helper->dirty_clip;
>> +	drm_clip_rect_reset(&helper->dirty_clip);
>> +	spin_unlock_irqrestore(&helper->dirty_lock, flags);
>> +
>> +	helper->fb->funcs->dirty(helper->fb, NULL, 0, 0, &clip, 1);
>> +}
>> +
>> +static void drm_fb_helper_dirty_init(struct drm_fb_helper *helper)
>> +{
>> +	spin_lock_init(&helper->dirty_lock);
>> +	INIT_WORK(&helper->dirty_work, drm_fb_helper_dirty_work);
>> +}
>> +
>> +static void drm_fb_helper_dirty(struct fb_info *info, u32 x, u32 y,
>> +				u32 width, u32 height)
>> +{
>> +	struct drm_fb_helper *helper = info->par;
>> +	struct drm_clip_rect clip;
>> +	unsigned long flags;
>> +
>> +	if (!helper->fb->funcs->dirty)
>> +		return;
>> +
>> +	clip.x1 = x;
>> +	clip.x2 = x + width;
>> +	clip.y1 = y;
>> +	clip.y2 = y + height;
>> +
>> +	spin_lock_irqsave(&helper->dirty_lock, flags);
>> +	drm_clip_rect_merge(&helper->dirty_clip, &clip, 1, 0, 0, 0);
>> +	spin_unlock_irqrestore(&helper->dirty_lock, flags);
>> +
>> +	schedule_work(&helper->dirty_work);
>> +}
>> +
>> +/**
>> + * drm_fb_helper_deferred_io() - fbdev deferred_io callback function
>> + * @info: fb_info struct pointer
>> + * @pagelist: list of dirty mmap framebuffer pages
>> + *
>> + * This function is used as the (struct fb_deferred_io *)->deferred_io
>> + * callback function for flushing the fbdev mmap writes.
>> + */
>> +void drm_fb_helper_deferred_io(struct fb_info *info,
>> +			       struct list_head *pagelist)
>> +{
>> +	unsigned long start, end, min, max;
>> +	struct page *page;
>> +	u32 y1, y2;
>> +
>> +	min = ULONG_MAX;
>> +	max = 0;
>> +	list_for_each_entry(page, pagelist, lru) {
>> +		start = page->index << PAGE_SHIFT;
>> +		end = start + PAGE_SIZE - 1;
>> +		min = min(min, start);
>> +		max = max(max, end);
>> +	}
>> +
>> +	if (min < max) {
>> +		y1 = min / info->fix.line_length;
>> +		y2 = min_t(u32, max / info->fix.line_length, info->var.yres);
>> +		drm_fb_helper_dirty(info, 0, y1, info->var.xres, y2 - y1);
>> +	}
>> +}
>> +EXPORT_SYMBOL(drm_fb_helper_deferred_io);
>> +
>> +#else
>> +static void drm_fb_helper_dirty_init(struct drm_fb_helper *helper)
>> +{
>> +}
>> +
>> +static void drm_fb_helper_dirty(struct fb_info *info, u32 x, u32 y,
>> +				u32 width, u32 height)
>> +{
>> +}
>> +#endif /* CONFIG_FB_DEFERRED_IO */
>> +
>>   /**
>>    * drm_fb_helper_sys_read - wrapper around fb_sys_read
>>    * @info: fb_info struct pointer
>> @@ -862,7 +968,14 @@ EXPORT_SYMBOL(drm_fb_helper_sys_read);
>>   ssize_t drm_fb_helper_sys_write(struct fb_info *info, const char __user *buf,
>>   				size_t count, loff_t *ppos)
>>   {
>> -	return fb_sys_write(info, buf, count, ppos);
>> +	ssize_t ret;
>> +
>> +	ret = fb_sys_write(info, buf, count, ppos);
>> +	if (ret > 0)
>> +		drm_fb_helper_dirty(info, 0, 0, info->var.xres,
>> +				    info->var.yres);
>> +
>> +	return ret;
>>   }
>>   EXPORT_SYMBOL(drm_fb_helper_sys_write);
>>
>> @@ -877,6 +990,8 @@ void drm_fb_helper_sys_fillrect(struct fb_info *info,
>>   				const struct fb_fillrect *rect)
>>   {
>>   	sys_fillrect(info, rect);
>> +	drm_fb_helper_dirty(info, rect->dx, rect->dy,
>> +			    rect->width, rect->height);
>>   }
>>   EXPORT_SYMBOL(drm_fb_helper_sys_fillrect);
>>
>> @@ -891,6 +1006,8 @@ void drm_fb_helper_sys_copyarea(struct fb_info *info,
>>   				const struct fb_copyarea *area)
>>   {
>>   	sys_copyarea(info, area);
>> +	drm_fb_helper_dirty(info, area->dx, area->dy,
>> +			    area->width, area->height);
>>   }
>>   EXPORT_SYMBOL(drm_fb_helper_sys_copyarea);
>>
>> @@ -905,6 +1022,8 @@ void drm_fb_helper_sys_imageblit(struct fb_info *info,
>>   				 const struct fb_image *image)
>>   {
>>   	sys_imageblit(info, image);
>> +	drm_fb_helper_dirty(info, image->dx, image->dy,
>> +			    image->width, image->height);
>>   }
>>   EXPORT_SYMBOL(drm_fb_helper_sys_imageblit);
>>
>> @@ -919,6 +1038,8 @@ void drm_fb_helper_cfb_fillrect(struct fb_info *info,
>>   				const struct fb_fillrect *rect)
>>   {
>>   	cfb_fillrect(info, rect);
>> +	drm_fb_helper_dirty(info, rect->dx, rect->dy,
>> +			    rect->width, rect->height);
>>   }
>>   EXPORT_SYMBOL(drm_fb_helper_cfb_fillrect);
>>
>> @@ -933,6 +1054,8 @@ void drm_fb_helper_cfb_copyarea(struct fb_info *info,
>>   				const struct fb_copyarea *area)
>>   {
>>   	cfb_copyarea(info, area);
>> +	drm_fb_helper_dirty(info, area->dx, area->dy,
>> +			    area->width, area->height);
>>   }
>>   EXPORT_SYMBOL(drm_fb_helper_cfb_copyarea);
>>
>> @@ -947,6 +1070,8 @@ void drm_fb_helper_cfb_imageblit(struct fb_info *info,
>>   				 const struct fb_image *image)
>>   {
>>   	cfb_imageblit(info, image);
>> +	drm_fb_helper_dirty(info, image->dx, image->dy,
>> +			    image->width, image->height);
>>   }
>>   EXPORT_SYMBOL(drm_fb_helper_cfb_imageblit);
>>
>> diff --git a/include/drm/drm_fb_helper.h b/include/drm/drm_fb_helper.h
>> index 062723b..dde825c 100644
>> --- a/include/drm/drm_fb_helper.h
>> +++ b/include/drm/drm_fb_helper.h
>> @@ -172,6 +172,10 @@ struct drm_fb_helper_connector {
>>    * @funcs: driver callbacks for fb helper
>>    * @fbdev: emulated fbdev device info struct
>>    * @pseudo_palette: fake palette of 16 colors
>> + * @dirty_clip: clip rectangle used with deferred_io to accumulate damage to
>> + *              the screen buffer
>> + * @dirty_lock: spinlock protecting @dirty_clip
>> + * @dirty_work: worker used to flush the framebuffer
>>    *
>>    * This is the main structure used by the fbdev helpers. Drivers supporting
>>    * fbdev emulation should embedded this into their overall driver structure.
>> @@ -189,6 +193,11 @@ struct drm_fb_helper {
>>   	const struct drm_fb_helper_funcs *funcs;
>>   	struct fb_info *fbdev;
>>   	u32 pseudo_palette[17];
>> +#ifdef CONFIG_FB_DEFERRED_IO
>> +	struct drm_clip_rect dirty_clip;
>> +	spinlock_t dirty_lock;
>> +	struct work_struct dirty_work;
>> +#endif
>>
>>   	/**
>>   	 * @kernel_fb_list:
>> @@ -245,6 +254,9 @@ void drm_fb_helper_fill_fix(struct fb_info *info, uint32_t pitch,
>>
>>   void drm_fb_helper_unlink_fbi(struct drm_fb_helper *fb_helper);
>>
>> +void drm_fb_helper_deferred_io(struct fb_info *info,
>> +			       struct list_head *pagelist);
>> +
>>   ssize_t drm_fb_helper_sys_read(struct fb_info *info, char __user *buf,
>>   			       size_t count, loff_t *ppos);
>>   ssize_t drm_fb_helper_sys_write(struct fb_info *info, const char __user *buf,
>> @@ -368,6 +380,11 @@ static inline void drm_fb_helper_unlink_fbi(struct drm_fb_helper *fb_helper)
>>   {
>>   }
>>
>> +static inline void drm_fb_helper_deferred_io(struct fb_info *info,
>> +					     struct list_head *pagelist)
>> +{
>> +}
>> +
>>   static inline ssize_t drm_fb_helper_sys_read(struct fb_info *info,
>>   					     char __user *buf, size_t count,
>>   					     loff_t *ppos)
>> --
>> 2.2.2
>>

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#1387733

On Tue, Apr 26, 2016 at 06:24:54PM +0200, Noralf Trønnes wrote:
> 
> Den 25.04.2016 11:09, skrev Daniel Vetter:
> >On Sun, Apr 24, 2016 at 10:48:58PM +0200, Noralf Trønnes wrote:
> >>This adds deferred io support if CONFIG_FB_DEFERRED_IO is enabled.
> >>The fbdev framebuffer changes are flushed using the callback
> >>(struct drm_framebuffer *)->funcs->dirty() by a dedicated worker
> >>ensuring that it always runs in process context.
> >>
> >>Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
> >>---
> >>
> >>Changes since v1:
> >>- Use a dedicated worker to run the framebuffer flushing like qxl does
> >>- Add parameter descriptions to drm_fb_helper_deferred_io
> >>
> >>  drivers/gpu/drm/drm_fb_helper.c | 127 +++++++++++++++++++++++++++++++++++++++-
> >>  include/drm/drm_fb_helper.h     |  17 ++++++
> >>  2 files changed, 143 insertions(+), 1 deletion(-)
> >>
> >>diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> >>index 855108e..46ee6f8 100644
> >>--- a/drivers/gpu/drm/drm_fb_helper.c
> >>+++ b/drivers/gpu/drm/drm_fb_helper.c
> >>@@ -40,6 +40,7 @@
> >>  #include <drm/drm_crtc_helper.h>
> >>  #include <drm/drm_atomic.h>
> >>  #include <drm/drm_atomic_helper.h>
> >>+#include <drm/drm_rect.h>
> >>
> >>  static bool drm_fbdev_emulation = true;
> >>  module_param_named(fbdev_emulation, drm_fbdev_emulation, bool, 0600);
> >>@@ -48,6 +49,10 @@ MODULE_PARM_DESC(fbdev_emulation,
> >>
> >>  static LIST_HEAD(kernel_fb_helper_list);
> >>
> >>+static void drm_fb_helper_dirty_init(struct drm_fb_helper *helper);
> >>+static void drm_fb_helper_dirty(struct fb_info *info, u32 x, u32 y,
> >>+				u32 width, u32 height);
> >>+
> >>  /**
> >>   * DOC: fbdev helpers
> >>   *
> >>@@ -84,6 +89,16 @@ static LIST_HEAD(kernel_fb_helper_list);
> >>   * and set up an initial configuration using the detected hardware, drivers
> >>   * should call drm_fb_helper_single_add_all_connectors() followed by
> >>   * drm_fb_helper_initial_config().
> >>+ *
> >>+ * If CONFIG_FB_DEFERRED_IO is enabled and
> >>+ * (struct drm_framebuffer *)->funcs->dirty is set, the
> >>+ * drm_fb_helper_{cfb,sys}_{write,fillrect,copyarea,imageblit} functions
> >>+ * will accumulate changes and schedule (struct fb_helper).dirty_work to run
> >>+ * right away. This worker then calls the dirty() function ensuring that it
> >>+ * will always run in process context since the fb_*() function could be
> >>+ * running in atomic context. If drm_fb_helper_deferred_io() is used as the
> >>+ * deferred_io callback it will also schedule dirty_work with the damage
> >>+ * collected from the mmap page writes.
> >One thing to consider (and personally I don't care either way) is whether
> >we shouldn't just select CONFIG_FB_DEFERRED_IO if the fbdev helpers are
> >enabled. Pushing that out to drivers is imo a bit fragile.
> >
> >But like I said I'm ok with either way.
> 
> My concern was adding code and data that only a few drivers would
> actually use. But of course there's the tradeoff with complexity.
> I use this to enable it:
>         select FB_DEFERRED_IO if DRM_KMS_FB_HELPER
> 
> I guess the maintainer has to make this choice between size and complexity
> :-)
> I can enable it by default if you want, drm is both huge and complex so I
> don't know what's best.
> 
> As a sidenote, I have also put all the fbdev code in a file of it's own to
> make it simple with regards to the DRM_FBDEV_EMULATION user option:
> tinydrm-$(CONFIG_DRM_KMS_FB_HELPER)     += tinydrm-fbdev.o

Ok, if you ask maintainers then please nuke the #ifdef from .c files. If
you select CONFIG_DRM_KMS_FB_HELPER, then you get hdmi, edid, dp aux, dp
mst and whatever else helpers, even if you don't need them. Adding 3
functions for defio when you select fbdev helpers and maybe don't need
them is totally harmless. And removing the #ifdef will look so much better
;-)

> 
> >>   */
> >>
> >>  /**
> >>@@ -401,11 +416,14 @@ backoff:
> >>  static int restore_fbdev_mode(struct drm_fb_helper *fb_helper)
> >>  {
> >>  	struct drm_device *dev = fb_helper->dev;
> >>+	struct fb_info *info = fb_helper->fbdev;
> >>  	struct drm_plane *plane;
> >>  	int i;
> >>
> >>  	drm_warn_on_modeset_not_all_locked(dev);
> >>
> >>+	drm_fb_helper_dirty(info, 0, 0, info->var.xres, info->var.yres);
> >Why is this needed? If you do a modeset (or pageflip or whatever) drivers
> >are supposed to re-upload the entire screen. We've talked about adding a
> >dirty rectangle to atomic to allow userspace to optimize this, but there
> >should _never_ be a need to do a dirtyfb call around a modeset. Probably
> >just a driver bug in your panel drm drivers?
> 
> Ok, in tinydrm I now set a flag in &drm_simple_display_pipe_funcs
> ->plane_update to indicate that the next dirty() should do the whole
> framebuffer which seems to work fine.
> Should I actually perform the update as well?
> If so I would need to add a worker in tinydrm to do that.

Yes, plane update should always do a full update. Not sure how you get
away with delaying that to ->dirty, maybe modesetting isn't
double-buffering when you don't have a GL that could do glamour.

->dirty is _only_ for frontbuffer rendering, not for page-flipping to an
entirely new buffer. In short if someone calls ->dirty on a buffer which
is currently not being displayed than a) they're silly b) drivers should
treat it as a no-op. Maybe we need a helper to do that ...
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

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#1388850

Den 26.04.2016 19:19, skrev Daniel Vetter:
> On Tue, Apr 26, 2016 at 06:24:54PM +0200, Noralf Trønnes wrote:
>> Den 25.04.2016 11:09, skrev Daniel Vetter:
>>> On Sun, Apr 24, 2016 at 10:48:58PM +0200, Noralf Trønnes wrote:
>>>> This adds deferred io support if CONFIG_FB_DEFERRED_IO is enabled.
>>>> The fbdev framebuffer changes are flushed using the callback
>>>> (struct drm_framebuffer *)->funcs->dirty() by a dedicated worker
>>>> ensuring that it always runs in process context.
>>>>
>>>> Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
>>>> ---
>>>>
>>>> Changes since v1:
>>>> - Use a dedicated worker to run the framebuffer flushing like qxl does
>>>> - Add parameter descriptions to drm_fb_helper_deferred_io
>>>>
>>>>   drivers/gpu/drm/drm_fb_helper.c | 127 +++++++++++++++++++++++++++++++++++++++-
>>>>   include/drm/drm_fb_helper.h     |  17 ++++++
>>>>   2 files changed, 143 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
>>>> index 855108e..46ee6f8 100644
>>>> --- a/drivers/gpu/drm/drm_fb_helper.c
>>>> +++ b/drivers/gpu/drm/drm_fb_helper.c
>>>> @@ -40,6 +40,7 @@
>>>>   #include <drm/drm_crtc_helper.h>
>>>>   #include <drm/drm_atomic.h>
>>>>   #include <drm/drm_atomic_helper.h>
>>>> +#include <drm/drm_rect.h>
>>>>
>>>>   static bool drm_fbdev_emulation = true;
>>>>   module_param_named(fbdev_emulation, drm_fbdev_emulation, bool, 0600);
>>>> @@ -48,6 +49,10 @@ MODULE_PARM_DESC(fbdev_emulation,
>>>>
>>>>   static LIST_HEAD(kernel_fb_helper_list);
>>>>
>>>> +static void drm_fb_helper_dirty_init(struct drm_fb_helper *helper);
>>>> +static void drm_fb_helper_dirty(struct fb_info *info, u32 x, u32 y,
>>>> +				u32 width, u32 height);
>>>> +
>>>>   /**
>>>>    * DOC: fbdev helpers
>>>>    *
>>>> @@ -84,6 +89,16 @@ static LIST_HEAD(kernel_fb_helper_list);
>>>>    * and set up an initial configuration using the detected hardware, drivers
>>>>    * should call drm_fb_helper_single_add_all_connectors() followed by
>>>>    * drm_fb_helper_initial_config().
>>>> + *
>>>> + * If CONFIG_FB_DEFERRED_IO is enabled and
>>>> + * (struct drm_framebuffer *)->funcs->dirty is set, the
>>>> + * drm_fb_helper_{cfb,sys}_{write,fillrect,copyarea,imageblit} functions
>>>> + * will accumulate changes and schedule (struct fb_helper).dirty_work to run
>>>> + * right away. This worker then calls the dirty() function ensuring that it
>>>> + * will always run in process context since the fb_*() function could be
>>>> + * running in atomic context. If drm_fb_helper_deferred_io() is used as the
>>>> + * deferred_io callback it will also schedule dirty_work with the damage
>>>> + * collected from the mmap page writes.
>>> One thing to consider (and personally I don't care either way) is whether
>>> we shouldn't just select CONFIG_FB_DEFERRED_IO if the fbdev helpers are
>>> enabled. Pushing that out to drivers is imo a bit fragile.
>>>
>>> But like I said I'm ok with either way.
>> My concern was adding code and data that only a few drivers would
>> actually use. But of course there's the tradeoff with complexity.
>> I use this to enable it:
>>          select FB_DEFERRED_IO if DRM_KMS_FB_HELPER
>>
>> I guess the maintainer has to make this choice between size and complexity
>> :-)
>> I can enable it by default if you want, drm is both huge and complex so I
>> don't know what's best.
>>
>> As a sidenote, I have also put all the fbdev code in a file of it's own to
>> make it simple with regards to the DRM_FBDEV_EMULATION user option:
>> tinydrm-$(CONFIG_DRM_KMS_FB_HELPER)     += tinydrm-fbdev.o
> Ok, if you ask maintainers then please nuke the #ifdef from .c files. If
> you select CONFIG_DRM_KMS_FB_HELPER, then you get hdmi, edid, dp aux, dp
> mst and whatever else helpers, even if you don't need them. Adding 3
> functions for defio when you select fbdev helpers and maybe don't need
> them is totally harmless. And removing the #ifdef will look so much better
> ;-)

Will do :-)
Kernel development is just my hobby so I'm not well versed in all of this.

>>>>    */
>>>>
>>>>   /**
>>>> @@ -401,11 +416,14 @@ backoff:
>>>>   static int restore_fbdev_mode(struct drm_fb_helper *fb_helper)
>>>>   {
>>>>   	struct drm_device *dev = fb_helper->dev;
>>>> +	struct fb_info *info = fb_helper->fbdev;
>>>>   	struct drm_plane *plane;
>>>>   	int i;
>>>>
>>>>   	drm_warn_on_modeset_not_all_locked(dev);
>>>>
>>>> +	drm_fb_helper_dirty(info, 0, 0, info->var.xres, info->var.yres);
>>> Why is this needed? If you do a modeset (or pageflip or whatever) drivers
>>> are supposed to re-upload the entire screen. We've talked about adding a
>>> dirty rectangle to atomic to allow userspace to optimize this, but there
>>> should _never_ be a need to do a dirtyfb call around a modeset. Probably
>>> just a driver bug in your panel drm drivers?
>> Ok, in tinydrm I now set a flag in &drm_simple_display_pipe_funcs
>> ->plane_update to indicate that the next dirty() should do the whole
>> framebuffer which seems to work fine.
>> Should I actually perform the update as well?
>> If so I would need to add a worker in tinydrm to do that.
> Yes, plane update should always do a full update. Not sure how you get
> away with delaying that to ->dirty, maybe modesetting isn't
> double-buffering when you don't have a GL that could do glamour.
>
> ->dirty is _only_ for frontbuffer rendering, not for page-flipping to an
> entirely new buffer. In short if someone calls ->dirty on a buffer which
> is currently not being displayed than a) they're silly b) drivers should
> treat it as a no-op. Maybe we need a helper to do that ...
> -Daniel

drm_fb_helper will call dirty() as long as there's fbdev activity, so the
driver needs to take that into account. For instance fbcon with a blinking
cursor will trigger calls even if a buffer has been set up on the drm side.
tinydrm checks the fb against the fb set on the plane and if it differs
it's a no-op.

Noralf.

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#1388899

On Wed, Apr 27, 2016 at 11:45:31AM +0200, Noralf Trønnes wrote:
> 
> Den 26.04.2016 19:19, skrev Daniel Vetter:
> >On Tue, Apr 26, 2016 at 06:24:54PM +0200, Noralf Trønnes wrote:
> >>Den 25.04.2016 11:09, skrev Daniel Vetter:
> >>>On Sun, Apr 24, 2016 at 10:48:58PM +0200, Noralf Trønnes wrote:
> >>>>This adds deferred io support if CONFIG_FB_DEFERRED_IO is enabled.
> >>>>The fbdev framebuffer changes are flushed using the callback
> >>>>(struct drm_framebuffer *)->funcs->dirty() by a dedicated worker
> >>>>ensuring that it always runs in process context.
> >>>>
> >>>>Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
> >>>>---
> >>>>
> >>>>Changes since v1:
> >>>>- Use a dedicated worker to run the framebuffer flushing like qxl does
> >>>>- Add parameter descriptions to drm_fb_helper_deferred_io
> >>>>
> >>>>  drivers/gpu/drm/drm_fb_helper.c | 127 +++++++++++++++++++++++++++++++++++++++-
> >>>>  include/drm/drm_fb_helper.h     |  17 ++++++
> >>>>  2 files changed, 143 insertions(+), 1 deletion(-)
> >>>>
> >>>>diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> >>>>index 855108e..46ee6f8 100644
> >>>>--- a/drivers/gpu/drm/drm_fb_helper.c
> >>>>+++ b/drivers/gpu/drm/drm_fb_helper.c
> >>>>@@ -40,6 +40,7 @@
> >>>>  #include <drm/drm_crtc_helper.h>
> >>>>  #include <drm/drm_atomic.h>
> >>>>  #include <drm/drm_atomic_helper.h>
> >>>>+#include <drm/drm_rect.h>
> >>>>
> >>>>  static bool drm_fbdev_emulation = true;
> >>>>  module_param_named(fbdev_emulation, drm_fbdev_emulation, bool, 0600);
> >>>>@@ -48,6 +49,10 @@ MODULE_PARM_DESC(fbdev_emulation,
> >>>>
> >>>>  static LIST_HEAD(kernel_fb_helper_list);
> >>>>
> >>>>+static void drm_fb_helper_dirty_init(struct drm_fb_helper *helper);
> >>>>+static void drm_fb_helper_dirty(struct fb_info *info, u32 x, u32 y,
> >>>>+				u32 width, u32 height);
> >>>>+
> >>>>  /**
> >>>>   * DOC: fbdev helpers
> >>>>   *
> >>>>@@ -84,6 +89,16 @@ static LIST_HEAD(kernel_fb_helper_list);
> >>>>   * and set up an initial configuration using the detected hardware, drivers
> >>>>   * should call drm_fb_helper_single_add_all_connectors() followed by
> >>>>   * drm_fb_helper_initial_config().
> >>>>+ *
> >>>>+ * If CONFIG_FB_DEFERRED_IO is enabled and
> >>>>+ * (struct drm_framebuffer *)->funcs->dirty is set, the
> >>>>+ * drm_fb_helper_{cfb,sys}_{write,fillrect,copyarea,imageblit} functions
> >>>>+ * will accumulate changes and schedule (struct fb_helper).dirty_work to run
> >>>>+ * right away. This worker then calls the dirty() function ensuring that it
> >>>>+ * will always run in process context since the fb_*() function could be
> >>>>+ * running in atomic context. If drm_fb_helper_deferred_io() is used as the
> >>>>+ * deferred_io callback it will also schedule dirty_work with the damage
> >>>>+ * collected from the mmap page writes.
> >>>One thing to consider (and personally I don't care either way) is whether
> >>>we shouldn't just select CONFIG_FB_DEFERRED_IO if the fbdev helpers are
> >>>enabled. Pushing that out to drivers is imo a bit fragile.
> >>>
> >>>But like I said I'm ok with either way.
> >>My concern was adding code and data that only a few drivers would
> >>actually use. But of course there's the tradeoff with complexity.
> >>I use this to enable it:
> >>         select FB_DEFERRED_IO if DRM_KMS_FB_HELPER
> >>
> >>I guess the maintainer has to make this choice between size and complexity
> >>:-)
> >>I can enable it by default if you want, drm is both huge and complex so I
> >>don't know what's best.
> >>
> >>As a sidenote, I have also put all the fbdev code in a file of it's own to
> >>make it simple with regards to the DRM_FBDEV_EMULATION user option:
> >>tinydrm-$(CONFIG_DRM_KMS_FB_HELPER)     += tinydrm-fbdev.o
> >Ok, if you ask maintainers then please nuke the #ifdef from .c files. If
> >you select CONFIG_DRM_KMS_FB_HELPER, then you get hdmi, edid, dp aux, dp
> >mst and whatever else helpers, even if you don't need them. Adding 3
> >functions for defio when you select fbdev helpers and maybe don't need
> >them is totally harmless. And removing the #ifdef will look so much better
> >;-)
> 
> Will do :-)
> Kernel development is just my hobby so I'm not well versed in all of this.

You're doing great tbh!

> >>>>   */
> >>>>
> >>>>  /**
> >>>>@@ -401,11 +416,14 @@ backoff:
> >>>>  static int restore_fbdev_mode(struct drm_fb_helper *fb_helper)
> >>>>  {
> >>>>  	struct drm_device *dev = fb_helper->dev;
> >>>>+	struct fb_info *info = fb_helper->fbdev;
> >>>>  	struct drm_plane *plane;
> >>>>  	int i;
> >>>>
> >>>>  	drm_warn_on_modeset_not_all_locked(dev);
> >>>>
> >>>>+	drm_fb_helper_dirty(info, 0, 0, info->var.xres, info->var.yres);
> >>>Why is this needed? If you do a modeset (or pageflip or whatever) drivers
> >>>are supposed to re-upload the entire screen. We've talked about adding a
> >>>dirty rectangle to atomic to allow userspace to optimize this, but there
> >>>should _never_ be a need to do a dirtyfb call around a modeset. Probably
> >>>just a driver bug in your panel drm drivers?
> >>Ok, in tinydrm I now set a flag in &drm_simple_display_pipe_funcs
> >>->plane_update to indicate that the next dirty() should do the whole
> >>framebuffer which seems to work fine.
> >>Should I actually perform the update as well?
> >>If so I would need to add a worker in tinydrm to do that.
> >Yes, plane update should always do a full update. Not sure how you get
> >away with delaying that to ->dirty, maybe modesetting isn't
> >double-buffering when you don't have a GL that could do glamour.
> >
> >->dirty is _only_ for frontbuffer rendering, not for page-flipping to an
> >entirely new buffer. In short if someone calls ->dirty on a buffer which
> >is currently not being displayed than a) they're silly b) drivers should
> >treat it as a no-op. Maybe we need a helper to do that ...
> >-Daniel
> 
> drm_fb_helper will call dirty() as long as there's fbdev activity, so the
> driver needs to take that into account. For instance fbcon with a blinking
> cursor will trigger calls even if a buffer has been set up on the drm side.
> tinydrm checks the fb against the fb set on the plane and if it differs
> it's a no-op.

Was really just an idea to make drivers a bit simpler, since pretty much
all of them we need to do this check. But with a grand total of just 3 (4
with tinydrm) implementing a non-trivial dirty callback that's not really
worth it I think.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

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