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[PATCH 2/5 v3] drm/bridge: adv7511: Switch to using drm_kms_helper_hotplug_event()

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  [PATCH 2/5 v3] drm/bridge: adv7511: Switch to using drm_kms_helper_hotplug_event() John Stultz <john.stultz@linaro.org> - 2017-01-03 20:50 +0100
    Re: [PATCH 2/5 v3] drm/bridge: adv7511: Switch to using drm_kms_helper_hotplug_event() Laurent Pinchart <laurent.pinchart@ideasonboard.com> - 2017-01-16 16:50 +0100
      Re: [PATCH 2/5 v3] drm/bridge: adv7511: Switch to using drm_kms_helper_hotplug_event() Laurent Pinchart <laurent.pinchart@ideasonboard.com> - 2017-01-16 17:00 +0100

#1550127 — [PATCH 2/5 v3] drm/bridge: adv7511: Switch to using drm_kms_helper_hotplug_event()

In chasing down a previous issue with EDID probing from calling
drm_helper_hpd_irq_event() from irq context, Laurent noticed
that the DRM documentation suggests that
drm_kms_helper_hotplug_event() should be used instead.

Thus this patch replaces drm_helper_hpd_irq_event() with
drm_kms_helper_hotplug_event(), which requires we update the
connector.status entry and only call _hotplug_event() when the
status changes.

Cc: David Airlie <airlied@linux.ie>
Cc: Archit Taneja <architt@codeaurora.org>
Cc: Wolfram Sang <wsa+renesas@sang-engineering.com>
Cc: Lars-Peter Clausen <lars@metafoo.de>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: John Stultz <john.stultz@linaro.org>
---
v3: Update connector.status value and only call __hotplug_event()
    when that status changes, as suggested by Laurent.

 drivers/gpu/drm/bridge/adv7511/adv7511_drv.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
index 4fcea44..d93d66f 100644
--- a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
+++ b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
@@ -405,8 +405,22 @@ static bool adv7511_hpd(struct adv7511 *adv7511)
 static void adv7511_hpd_work(struct work_struct *work)
 {
 	struct adv7511 *adv7511 = container_of(work, struct adv7511, hpd_work);
+	enum drm_connector_status status;
+	unsigned int val;
+	int ret;
+
+	ret = regmap_read(adv7511->regmap, ADV7511_REG_STATUS, &val);
+	if (ret < 0)
+		status = connector_status_disconnected;
+	else if (val & ADV7511_STATUS_HPD)
+		status = connector_status_connected;
+	else
+		status = connector_status_disconnected;
+
+	if (adv7511->connector.status != status)
+		drm_kms_helper_hotplug_event(adv7511->connector.dev);
 
-	drm_helper_hpd_irq_event(adv7511->connector.dev);
+	adv7511->connector.status = status;
 }
 
 static int adv7511_irq_process(struct adv7511 *adv7511, bool process_hpd)
-- 
2.7.4

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#1559848

Hi John,

Thank you for the patch.

On Tuesday 03 Jan 2017 11:41:39 John Stultz wrote:
> In chasing down a previous issue with EDID probing from calling
> drm_helper_hpd_irq_event() from irq context, Laurent noticed
> that the DRM documentation suggests that
> drm_kms_helper_hotplug_event() should be used instead.
> 
> Thus this patch replaces drm_helper_hpd_irq_event() with
> drm_kms_helper_hotplug_event(), which requires we update the
> connector.status entry and only call _hotplug_event() when the
> status changes.
> 
> Cc: David Airlie <airlied@linux.ie>
> Cc: Archit Taneja <architt@codeaurora.org>
> Cc: Wolfram Sang <wsa+renesas@sang-engineering.com>
> Cc: Lars-Peter Clausen <lars@metafoo.de>
> Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> Cc: dri-devel@lists.freedesktop.org
> Signed-off-by: John Stultz <john.stultz@linaro.org>
> ---
> v3: Update connector.status value and only call __hotplug_event()
>     when that status changes, as suggested by Laurent.
> 
>  drivers/gpu/drm/bridge/adv7511/adv7511_drv.c | 16 +++++++++++++++-
>  1 file changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
> b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c index 4fcea44..d93d66f
> 100644
> --- a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
> +++ b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
> @@ -405,8 +405,22 @@ static bool adv7511_hpd(struct adv7511 *adv7511)
>  static void adv7511_hpd_work(struct work_struct *work)
>  {
>  	struct adv7511 *adv7511 = container_of(work, struct adv7511, 
hpd_work);
> +	enum drm_connector_status status;
> +	unsigned int val;
> +	int ret;
> +
> +	ret = regmap_read(adv7511->regmap, ADV7511_REG_STATUS, &val);
> +	if (ret < 0)
> +		status = connector_status_disconnected;
> +	else if (val & ADV7511_STATUS_HPD)
> +		status = connector_status_connected;
> +	else
> +		status = connector_status_disconnected;
> +
> +	if (adv7511->connector.status != status)
> +		drm_kms_helper_hotplug_event(adv7511->connector.dev);
> 
> -	drm_helper_hpd_irq_event(adv7511->connector.dev);
> +	adv7511->connector.status = status;

Shouldn't you update the status before calling drm_kms_helper_hotplug_event() 
? Doing it after not only creates a small race condition as 
drm_kms_helper_hotplug_event() sends an event to userspace that could result 
in an ioctl call to retrieve the status, but the status is also checked by 
drm_setup_crtcs() called by drm_fb_helper_hotplug_event().

>  }
> 
>  static int adv7511_irq_process(struct adv7511 *adv7511, bool process_hpd)

-- 
Regards,

Laurent Pinchart

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#1559852

On Monday 16 Jan 2017 17:47:46 Laurent Pinchart wrote:
> Hi John,
> 
> Thank you for the patch.
> 
> On Tuesday 03 Jan 2017 11:41:39 John Stultz wrote:
> > In chasing down a previous issue with EDID probing from calling
> > drm_helper_hpd_irq_event() from irq context, Laurent noticed
> > that the DRM documentation suggests that
> > drm_kms_helper_hotplug_event() should be used instead.
> > 
> > Thus this patch replaces drm_helper_hpd_irq_event() with
> > drm_kms_helper_hotplug_event(), which requires we update the
> > connector.status entry and only call _hotplug_event() when the
> > status changes.
> > 
> > Cc: David Airlie <airlied@linux.ie>
> > Cc: Archit Taneja <architt@codeaurora.org>
> > Cc: Wolfram Sang <wsa+renesas@sang-engineering.com>
> > Cc: Lars-Peter Clausen <lars@metafoo.de>
> > Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> > Cc: dri-devel@lists.freedesktop.org
> > Signed-off-by: John Stultz <john.stultz@linaro.org>
> > ---
> > v3: Update connector.status value and only call __hotplug_event()
> > 
> >     when that status changes, as suggested by Laurent.
> >  
> >  drivers/gpu/drm/bridge/adv7511/adv7511_drv.c | 16 +++++++++++++++-
> >  1 file changed, 15 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
> > b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c index 4fcea44..d93d66f
> > 100644
> > --- a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
> > +++ b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
> > @@ -405,8 +405,22 @@ static bool adv7511_hpd(struct adv7511 *adv7511)
> > 
> >  static void adv7511_hpd_work(struct work_struct *work)
> >  {
> >  
> >  	struct adv7511 *adv7511 = container_of(work, struct adv7511,
> 
> hpd_work);
> 
> > +	enum drm_connector_status status;
> > +	unsigned int val;
> > +	int ret;
> > +
> > +	ret = regmap_read(adv7511->regmap, ADV7511_REG_STATUS, &val);
> > +	if (ret < 0)
> > +		status = connector_status_disconnected;
> > +	else if (val & ADV7511_STATUS_HPD)
> > +		status = connector_status_connected;
> > +	else
> > +		status = connector_status_disconnected;
> > +
> > +	if (adv7511->connector.status != status)
> > +		drm_kms_helper_hotplug_event(adv7511->connector.dev);
> > 
> > -	drm_helper_hpd_irq_event(adv7511->connector.dev);
> > +	adv7511->connector.status = status;
> 
> Shouldn't you update the status before calling
> drm_kms_helper_hotplug_event() ? Doing it after not only creates a small
> race condition as
> drm_kms_helper_hotplug_event() sends an event to userspace that could result
> in an ioctl call to retrieve the status, but the status is also checked by
> drm_setup_crtcs() called by drm_fb_helper_hotplug_event().

With

        if (adv7511->connector.status != status) {
                adv7511->connector.status = status;
                drm_kms_helper_hotplug_event(adv7511->connector.dev);
        }

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Tested-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

> >  }
> >  
> >  static int adv7511_irq_process(struct adv7511 *adv7511, bool process_hpd)

-- 
Regards,

Laurent Pinchart

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