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[PATCH 00/20] MIPS: SEAD3 device tree conversion

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  [PATCH 00/20] MIPS: SEAD3 device tree conversion Paul Burton <paul.burton@imgtec.com> - 2016-08-09 14:40 +0200
    [PATCH 02/20] MIPS: SEAD3: Probe interrupt controllers using DT Paul Burton <paul.burton@imgtec.com> - 2016-08-09 14:40 +0200
      Re: [PATCH 02/20] MIPS: SEAD3: Probe interrupt controllers using DT kbuild test robot <lkp@intel.com> - 2016-08-10 20:30 +0200
    [PATCH 12/20] MIPS: SEAD3: Reset via generic syscon-reboot driver & DT Paul Burton <paul.burton@imgtec.com> - 2016-08-09 14:40 +0200
    [PATCH 01/20] MIPS: SEAD3: Split obj-y entries across lines Paul Burton <paul.burton@imgtec.com> - 2016-08-09 14:40 +0200
    [PATCH 07/20] MIPS: SEAD3: Probe EHCI controller using DT Paul Burton <paul.burton@imgtec.com> - 2016-08-09 14:40 +0200
    [PATCH 05/20] MIPS: SEAD3: Probe ethernet controller using DT Paul Burton <paul.burton@imgtec.com> - 2016-08-09 14:40 +0200
    [PATCH 14/20] MIPS: SEAD3: Parse memsize in DT shim Paul Burton <paul.burton@imgtec.com> - 2016-08-09 14:40 +0200
    [PATCH 06/20] usb: host: ehci-sead3: Support probing using device tree Paul Burton <paul.burton@imgtec.com> - 2016-08-09 14:40 +0200
      Re: [PATCH 06/20] usb: host: ehci-sead3: Support probing using device tree Jonas Gorski <jonas.gorski@gmail.com> - 2016-08-09 16:10 +0200
    [PATCH 11/20] leds: Remove SEAD3 driver Paul Burton <paul.burton@imgtec.com> - 2016-08-09 14:40 +0200
    [PATCH 08/20] usb: host: ehci-sead3: Remove non-DT probe code Paul Burton <paul.burton@imgtec.com> - 2016-08-09 14:40 +0200
      Re: [PATCH 08/20] usb: host: ehci-sead3: Remove non-DT probe code Alan Stern <stern@rowland.harvard.edu> - 2016-08-09 16:30 +0200
    [PATCH 03/20] MIPS: SEAD3: Probe UARTs using DT Paul Burton <paul.burton@imgtec.com> - 2016-08-09 14:40 +0200
      Re: [PATCH 03/20] MIPS: SEAD3: Probe UARTs using DT kbuild test robot <lkp@intel.com> - 2016-08-10 20:30 +0200
      Re: [PATCH 03/20] MIPS: SEAD3: Probe UARTs using DT kbuild test robot <lkp@intel.com> - 2016-08-10 21:40 +0200
    [PATCH 04/20] MIPS: SEAD3: Use generic ns16550a earlycon support Paul Burton <paul.burton@imgtec.com> - 2016-08-09 14:40 +0200
    [PATCH 13/20] MIPS: SEAD3: Use generic restart-poweroff driver Paul Burton <paul.burton@imgtec.com> - 2016-08-09 14:40 +0200
    [PATCH 15/20] MIPS: SEAD3: Drop use of cobalt fbdev driver Paul Burton <paul.burton@imgtec.com> - 2016-08-09 14:50 +0200
    [PATCH 19/20] MIPS: SEAD3: Use img-ascii-lcd driver Paul Burton <paul.burton@imgtec.com> - 2016-08-09 14:50 +0200
    [PATCH 17/20] dt-bindings: img-ascii-lcd: Document a binding for simple ASCII LCDs Paul Burton <paul.burton@imgtec.com> - 2016-08-09 14:50 +0200
    [PATCH 16/20] fbdev: cobalt_lcdfb: Drop SEAD3 support Paul Burton <paul.burton@imgtec.com> - 2016-08-09 14:50 +0200
      Re: [PATCH 16/20] fbdev: cobalt_lcdfb: Drop SEAD3 support Tomi Valkeinen <tomi.valkeinen@ti.com> - 2016-08-10 20:50 +0200
    [PATCH 20/20] MIPS: SEAD3: Remove custom read_persistent_clock Paul Burton <paul.burton@imgtec.com> - 2016-08-09 14:50 +0200
    [PATCH 18/20] auxdisplay: img-ascii-lcd: driver for simple ASCII LCD displays Paul Burton <paul.burton@imgtec.com> - 2016-08-09 14:50 +0200

Page 2 of 2 — ← Prev page 1 [2]

#1458702 — [PATCH 17/20] dt-bindings: img-ascii-lcd: Document a binding for simple ASCII LCDs

Add documentation for a devicetree binding for the simple ASCII LCD
displays found on development boards such as the MIPS Boston, MIPS Malta
& MIPS SEAD3 from Imagination Technologies.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
---

 .../devicetree/bindings/auxdisplay/img-ascii-lcd.txt    | 17 +++++++++++++++++
 MAINTAINERS                                             |  5 +++++
 2 files changed, 22 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/auxdisplay/img-ascii-lcd.txt

diff --git a/Documentation/devicetree/bindings/auxdisplay/img-ascii-lcd.txt b/Documentation/devicetree/bindings/auxdisplay/img-ascii-lcd.txt
new file mode 100644
index 0000000..b69bb68
--- /dev/null
+++ b/Documentation/devicetree/bindings/auxdisplay/img-ascii-lcd.txt
@@ -0,0 +1,17 @@
+Binding for ASCII LCD displays on Imagination Technologies boards
+
+Required properties:
+- compatible : should be one of:
+    "img,boston-lcd"
+    "mti,malta-lcd"
+    "mti,sead3-lcd"
+
+Required properties for "img,boston-lcd":
+- reg : memory region locating the device registers
+
+Required properties for "mti,malta-lcd" or "mti,sead3-lcd":
+- regmap: phandle of the system controller containing the LCD registers
+- offset: offset in bytes to the LCD registers within the system controller
+
+The layout of the registers & properties of the display are determined
+from the compatible string, making this binding somewhat trivial.
diff --git a/MAINTAINERS b/MAINTAINERS
index 20bb1d0..d08cf6d 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1971,6 +1971,11 @@ S:	Maintained
 F:	Documentation/hwmon/asc7621
 F:	drivers/hwmon/asc7621.c
 
+ASCII LCD DRIVER
+M:	Paul Burton <paul.burton@imgtec.com>
+S:	Maintained
+F:	Documentation/devicetree/bindings/ascii-lcd.txt
+
 ASUS NOTEBOOKS AND EEEPC ACPI/WMI EXTRAS DRIVERS
 M:	Corentin Chary <corentin.chary@gmail.com>
 L:	acpi4asus-user@lists.sourceforge.net
-- 
2.9.2

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#1458704 — [PATCH 16/20] fbdev: cobalt_lcdfb: Drop SEAD3 support

The SEAD3 board no longer uses the cobalt_lcdfb driver, so remove the
SEAD3-specific code from it.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
---

 drivers/video/fbdev/Kconfig        |  2 +-
 drivers/video/fbdev/cobalt_lcdfb.c | 42 --------------------------------------
 2 files changed, 1 insertion(+), 43 deletions(-)

diff --git a/drivers/video/fbdev/Kconfig b/drivers/video/fbdev/Kconfig
index 88b008f..914bfb2 100644
--- a/drivers/video/fbdev/Kconfig
+++ b/drivers/video/fbdev/Kconfig
@@ -2183,7 +2183,7 @@ config FB_GOLDFISH
 
 config FB_COBALT
 	tristate "Cobalt server LCD frame buffer support"
-	depends on FB && (MIPS_COBALT || MIPS_SEAD3)
+	depends on FB && MIPS_COBALT
 
 config FB_SH7760
 	bool "SH7760/SH7763/SH7720/SH7721 LCDC support"
diff --git a/drivers/video/fbdev/cobalt_lcdfb.c b/drivers/video/fbdev/cobalt_lcdfb.c
index 07675d6..2d3b691 100644
--- a/drivers/video/fbdev/cobalt_lcdfb.c
+++ b/drivers/video/fbdev/cobalt_lcdfb.c
@@ -63,7 +63,6 @@
 #define LCD_CUR_POS(x)		((x) & LCD_CUR_POS_MASK)
 #define LCD_TEXT_POS(x)		((x) | LCD_TEXT_MODE)
 
-#ifdef CONFIG_MIPS_COBALT
 static inline void lcd_write_control(struct fb_info *info, u8 control)
 {
 	writel((u32)control << 24, info->screen_base);
@@ -83,47 +82,6 @@ static inline u8 lcd_read_data(struct fb_info *info)
 {
 	return readl(info->screen_base + LCD_DATA_REG_OFFSET) >> 24;
 }
-#else
-
-#define LCD_CTL			0x00
-#define LCD_DATA		0x08
-#define CPLD_STATUS		0x10
-#define CPLD_DATA		0x18
-
-static inline void cpld_wait(struct fb_info *info)
-{
-	do {
-	} while (readl(info->screen_base + CPLD_STATUS) & 1);
-}
-
-static inline void lcd_write_control(struct fb_info *info, u8 control)
-{
-	cpld_wait(info);
-	writel(control, info->screen_base + LCD_CTL);
-}
-
-static inline u8 lcd_read_control(struct fb_info *info)
-{
-	cpld_wait(info);
-	readl(info->screen_base + LCD_CTL);
-	cpld_wait(info);
-	return readl(info->screen_base + CPLD_DATA) & 0xff;
-}
-
-static inline void lcd_write_data(struct fb_info *info, u8 data)
-{
-	cpld_wait(info);
-	writel(data, info->screen_base + LCD_DATA);
-}
-
-static inline u8 lcd_read_data(struct fb_info *info)
-{
-	cpld_wait(info);
-	readl(info->screen_base + LCD_DATA);
-	cpld_wait(info);
-	return readl(info->screen_base + CPLD_DATA) & 0xff;
-}
-#endif
 
 static int lcd_busy_wait(struct fb_info *info)
 {
-- 
2.9.2

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#1459500 — Re: [PATCH 16/20] fbdev: cobalt_lcdfb: Drop SEAD3 support

[Multipart message — attachments visible in raw view] — view raw

On 09/08/16 15:35, Paul Burton wrote:
> The SEAD3 board no longer uses the cobalt_lcdfb driver, so remove the
> SEAD3-specific code from it.
> 
> Signed-off-by: Paul Burton <paul.burton@imgtec.com>
> ---
> 
>  drivers/video/fbdev/Kconfig        |  2 +-
>  drivers/video/fbdev/cobalt_lcdfb.c | 42 --------------------------------------
>  2 files changed, 1 insertion(+), 43 deletions(-)

Acked-by: Tomi Valkeinen <tomi.valkeinen@ti.com>

 Tomi

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#1458705 — [PATCH 20/20] MIPS: SEAD3: Remove custom read_persistent_clock

The SEAD3 board defines a custom implementation of read_persistent_clock
which does exactly the same dummy operation as the generic weak version.
Remove the not really implemented custom version.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>

---

 arch/mips/mti-sead3/sead3-time.c | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/arch/mips/mti-sead3/sead3-time.c b/arch/mips/mti-sead3/sead3-time.c
index 10b0bf3..71feb51 100644
--- a/arch/mips/mti-sead3/sead3-time.c
+++ b/arch/mips/mti-sead3/sead3-time.c
@@ -63,12 +63,6 @@ static unsigned int __init estimate_cpu_frequency(void)
 	return freq ;
 }
 
-void read_persistent_clock(struct timespec *ts)
-{
-	ts->tv_sec = 0;
-	ts->tv_nsec = 0;
-}
-
 int get_c0_perfcount_int(void)
 {
 	if (gic_present)
-- 
2.9.2

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#1458710 — [PATCH 18/20] auxdisplay: img-ascii-lcd: driver for simple ASCII LCD displays

Add a driver for simple ASCII LCD displays found on the MIPS Boston,
Malta & SEAD3 development boards. The Boston display is an independent
memory mapped device with a simple memory mapped 8 byte register space
containing the 8 ASCII characters to display. The Malta display is
exposed as part of the Malta board registers, and provides 8 registers
each of which corresponds to one of the ASCII characters to display. The
SEAD3 display is slightly more complex, exposing an interface to an
S6A0069 LCD controller via registers provided by the boards CPLD.
However although the displays differ in their register interface, we
require similar functionality on each board so abstracting away the
differences within a single driver allows us to share a significant
amount of code & ensure consistent behaviour.

The driver displays the Linux kernel version as the default message, but
allows the message to be changed via a character device. Messages longer
then the number of characters that the display can show will scroll.

This provides different behaviour to the existing LCD display code for
the MIPS Malta or MIPS SEAD3 platforms in the following ways:

  - The default string to display is not "LINUX ON MALTA" or "LINUX ON
    SEAD3" but "Linux" followed by the version number of the kernel
    (UTS_RELEASE).

  - Since that string tends to be significantly longer it scrolls twice
    as fast, moving every 500ms rather than every 1s.

  - The LCD won't be updated until the driver is probed, so it doesn't
    provide the early "LINUX" string.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
---

 MAINTAINERS                        |   1 +
 drivers/auxdisplay/Kconfig         |   9 +
 drivers/auxdisplay/Makefile        |   1 +
 drivers/auxdisplay/img-ascii-lcd.c | 443 +++++++++++++++++++++++++++++++++++++
 4 files changed, 454 insertions(+)
 create mode 100644 drivers/auxdisplay/img-ascii-lcd.c

diff --git a/MAINTAINERS b/MAINTAINERS
index d08cf6d..56cfecf 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1975,6 +1975,7 @@ ASCII LCD DRIVER
 M:	Paul Burton <paul.burton@imgtec.com>
 S:	Maintained
 F:	Documentation/devicetree/bindings/ascii-lcd.txt
+F:	drivers/auxdisplay/ascii-lcd.c
 
 ASUS NOTEBOOKS AND EEEPC ACPI/WMI EXTRAS DRIVERS
 M:	Corentin Chary <corentin.chary@gmail.com>
diff --git a/drivers/auxdisplay/Kconfig b/drivers/auxdisplay/Kconfig
index c07e725..10e1b9e 100644
--- a/drivers/auxdisplay/Kconfig
+++ b/drivers/auxdisplay/Kconfig
@@ -119,4 +119,13 @@ config CFAG12864B_RATE
 	  If you compile this as a module, you can still override this
 	  value using the module parameters.
 
+config IMG_ASCII_LCD
+	tristate "Imagination Technologies ASCII LCD Display"
+	default y if MIPS_MALTA || MIPS_SEAD3
+	select SYSCON
+	help
+	  Enable this to support the simple ASCII LCD displays found on
+	  development boards such as the MIPS Boston, MIPS Malta & MIPS SEAD3
+	  from Imagination Technologies.
+
 endif # AUXDISPLAY
diff --git a/drivers/auxdisplay/Makefile b/drivers/auxdisplay/Makefile
index 8a8936a..3127175 100644
--- a/drivers/auxdisplay/Makefile
+++ b/drivers/auxdisplay/Makefile
@@ -4,3 +4,4 @@
 
 obj-$(CONFIG_KS0108)		+= ks0108.o
 obj-$(CONFIG_CFAG12864B)	+= cfag12864b.o cfag12864bfb.o
+obj-$(CONFIG_IMG_ASCII_LCD)	+= img-ascii-lcd.o
diff --git a/drivers/auxdisplay/img-ascii-lcd.c b/drivers/auxdisplay/img-ascii-lcd.c
new file mode 100644
index 0000000..bf43b5d
--- /dev/null
+++ b/drivers/auxdisplay/img-ascii-lcd.c
@@ -0,0 +1,443 @@
+/*
+ * Copyright (C) 2016 Imagination Technologies
+ * Author: Paul Burton <paul.burton@imgtec.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2 of the License, or (at your
+ * option) any later version.
+ */
+
+#include <generated/utsrelease.h>
+#include <linux/kernel.h>
+#include <linux/io.h>
+#include <linux/mfd/syscon.h>
+#include <linux/module.h>
+#include <linux/of_address.h>
+#include <linux/of_platform.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/slab.h>
+#include <linux/sysfs.h>
+
+struct img_ascii_lcd_ctx;
+
+/**
+ * struct img_ascii_lcd_config - Configuration information about an LCD model
+ * @num_chars: the number of characters the LCD can display
+ * @external_regmap: true if registers are in a system controller, else false
+ * @update: function called to update the LCD
+ */
+struct img_ascii_lcd_config {
+	unsigned int num_chars;
+	bool external_regmap;
+	void (*update)(struct img_ascii_lcd_ctx *ctx);
+};
+
+/**
+ * struct img_ascii_lcd_ctx - Private data structure
+ * @pdev: the ASCII LCD platform device
+ * @base: the base address of the LCD registers
+ * @regmap: the regmap through which LCD registers are accessed
+ * @offset: the offset within regmap to the start of the LCD registers
+ * @cfg: pointer to the LCD model configuration
+ * @message: the full message to display or scroll on the LCD
+ * @message_len: the length of the @message string
+ * @scroll_pos: index of the first character of @message currently displayed
+ * @scroll_rate: scroll interval in jiffies
+ * @timer: timer used to implement scrolling
+ * @curr: the string currently displayed on the LCD
+ */
+struct img_ascii_lcd_ctx {
+	struct platform_device *pdev;
+	union {
+		void __iomem *base;
+		struct regmap *regmap;
+	};
+	u32 offset;
+	const struct img_ascii_lcd_config *cfg;
+	char *message;
+	unsigned int message_len;
+	unsigned int scroll_pos;
+	unsigned int scroll_rate;
+	struct timer_list timer;
+	char curr[] __aligned(8);
+};
+
+/*
+ * MIPS Boston development board
+ */
+
+static void boston_update(struct img_ascii_lcd_ctx *ctx)
+{
+	ulong val;
+
+#if BITS_PER_LONG == 64
+	val = *((u64 *)&ctx->curr[0]);
+	__raw_writeq(val, ctx->base);
+#elif BITS_PER_LONG == 32
+	val = *((u32 *)&ctx->curr[0]);
+	__raw_writel(val, ctx->base);
+	val = *((u32 *)&ctx->curr[4]);
+	__raw_writel(val, ctx->base + 4);
+#else
+# error Not 32 or 64 bit
+#endif
+}
+
+static struct img_ascii_lcd_config boston_config = {
+	.num_chars = 8,
+	.update = boston_update,
+};
+
+/*
+ * MIPS Malta development board
+ */
+
+static void malta_update(struct img_ascii_lcd_ctx *ctx)
+{
+	unsigned int i;
+	int err;
+
+	for (i = 0; i < ctx->cfg->num_chars; i++) {
+		err = regmap_write(ctx->regmap,
+				   ctx->offset + (i * 8), ctx->curr[i]);
+		if (err)
+			break;
+	}
+
+	if (unlikely(err))
+		pr_err_ratelimited("Failed to update LCD display: %d\n", err);
+}
+
+static struct img_ascii_lcd_config malta_config = {
+	.num_chars = 8,
+	.external_regmap = true,
+	.update = malta_update,
+};
+
+/*
+ * MIPS SEAD3 development board
+ */
+
+enum {
+	SEAD3_REG_LCD_CTRL		= 0x00,
+#define SEAD3_REG_LCD_CTRL_SETDRAM	BIT(7)
+	SEAD3_REG_LCD_DATA		= 0x08,
+	SEAD3_REG_CPLD_STATUS		= 0x10,
+#define SEAD3_REG_CPLD_STATUS_BUSY	BIT(0)
+	SEAD3_REG_CPLD_DATA		= 0x18,
+#define SEAD3_REG_CPLD_DATA_BUSY	BIT(7)
+};
+
+static int sead3_wait_sm_idle(struct img_ascii_lcd_ctx *ctx)
+{
+	unsigned int status;
+	int err;
+
+	do {
+		err = regmap_read(ctx->regmap,
+				  ctx->offset + SEAD3_REG_CPLD_STATUS,
+				  &status);
+		if (err)
+			return err;
+	} while (status & SEAD3_REG_CPLD_STATUS_BUSY);
+
+	return 0;
+
+}
+
+static int sead3_wait_lcd_idle(struct img_ascii_lcd_ctx *ctx)
+{
+	unsigned int cpld_data;
+	int err;
+
+	err = sead3_wait_sm_idle(ctx);
+	if (err)
+		return err;
+
+	do {
+		err = regmap_read(ctx->regmap,
+				  ctx->offset + SEAD3_REG_LCD_CTRL,
+				  &cpld_data);
+		if (err)
+			return err;
+
+		err = sead3_wait_sm_idle(ctx);
+		if (err)
+			return err;
+
+		err = regmap_read(ctx->regmap,
+				  ctx->offset + SEAD3_REG_CPLD_DATA,
+				  &cpld_data);
+		if (err)
+			return err;
+	} while (cpld_data & SEAD3_REG_CPLD_DATA_BUSY);
+
+	return 0;
+}
+
+static void sead3_update(struct img_ascii_lcd_ctx *ctx)
+{
+	unsigned int i;
+	int err;
+
+	for (i = 0; i < ctx->cfg->num_chars; i++) {
+		err = sead3_wait_lcd_idle(ctx);
+		if (err)
+			break;
+
+		err = regmap_write(ctx->regmap,
+				   ctx->offset + SEAD3_REG_LCD_CTRL,
+				   SEAD3_REG_LCD_CTRL_SETDRAM | i);
+		if (err)
+			break;
+
+		err = sead3_wait_lcd_idle(ctx);
+		if (err)
+			break;
+
+		err = regmap_write(ctx->regmap,
+				   ctx->offset + SEAD3_REG_LCD_DATA,
+				   ctx->curr[i]);
+		if (err)
+			break;
+	}
+
+	if (unlikely(err))
+		pr_err_ratelimited("Failed to update LCD display: %d\n", err);
+}
+
+static struct img_ascii_lcd_config sead3_config = {
+	.num_chars = 16,
+	.external_regmap = true,
+	.update = sead3_update,
+};
+
+static const struct of_device_id img_ascii_lcd_matches[] = {
+	{ .compatible = "img,boston-lcd", .data = &boston_config },
+	{ .compatible = "mti,malta-lcd", .data = &malta_config },
+	{ .compatible = "mti,sead3-lcd", .data = &sead3_config },
+};
+
+/**
+ * img_ascii_lcd_scroll() - scroll the display by a character
+ * @arg: really a pointer to the private data structure
+ *
+ * Scroll the current message along the LCD by one character, rearming the
+ * timer if required.
+ */
+static void img_ascii_lcd_scroll(unsigned long arg)
+{
+	struct img_ascii_lcd_ctx *ctx = (struct img_ascii_lcd_ctx *)arg;
+	unsigned int i, ch = ctx->scroll_pos;
+	unsigned int num_chars = ctx->cfg->num_chars;
+
+	/* update the current message string */
+	for (i = 0; i < num_chars;) {
+		/* copy as many characters from the string as possible */
+		for (; i < num_chars && ch < ctx->message_len; i++, ch++)
+			ctx->curr[i] = ctx->message[ch];
+
+		/* wrap around to the start of the string */
+		ch = 0;
+	}
+
+	/* update the LCD */
+	ctx->cfg->update(ctx);
+
+	/* move on to the next character */
+	ctx->scroll_pos++;
+	ctx->scroll_pos %= ctx->message_len;
+
+	/* rearm the timer */
+	if (ctx->message_len > ctx->cfg->num_chars)
+		mod_timer(&ctx->timer, jiffies + ctx->scroll_rate);
+}
+
+/**
+ * img_ascii_lcd_display() - set the message to be displayed
+ * @ctx: pointer to the private data structure
+ * @msg: the message to display
+ * @count: length of msg, or -1
+ *
+ * Display a new message @msg on the LCD. @msg can be longer than the number of
+ * characters the LCD can display, in which case it will begin scrolling across
+ * the LCD display.
+ *
+ * Return: 0 on success, -ENOMEM on memory allocation failure
+ */
+static int img_ascii_lcd_display(struct img_ascii_lcd_ctx *ctx,
+			     const char *msg, ssize_t count)
+{
+	char *new_msg;
+
+	/* stop the scroll timer */
+	del_timer_sync(&ctx->timer);
+
+	if (count == -1)
+		count = strlen(msg);
+
+	/* if the string ends with a newline, trim it */
+	if (msg[count - 1] == '\n')
+		count--;
+
+	new_msg = devm_kmalloc(&ctx->pdev->dev, count + 1, GFP_KERNEL);
+	if (!new_msg)
+		return -ENOMEM;
+
+	memcpy(new_msg, msg, count);
+	new_msg[count] = 0;
+
+	if (ctx->message)
+		devm_kfree(&ctx->pdev->dev, ctx->message);
+
+	ctx->message = new_msg;
+	ctx->message_len = count;
+	ctx->scroll_pos = 0;
+
+	/* update the LCD */
+	img_ascii_lcd_scroll((unsigned long)ctx);
+
+	return 0;
+}
+
+/**
+ * message_show() - read message via sysfs
+ * @dev: the LCD device
+ * @attr: the LCD message attribute
+ * @buf: the buffer to read the message into
+ *
+ * Read the current message being displayed or scrolled across the LCD display
+ * into @buf, for reads from sysfs.
+ *
+ * Return: the number of characters written to @buf
+ */
+static ssize_t message_show(struct device *dev, struct device_attribute *attr,
+			    char *buf)
+{
+	struct img_ascii_lcd_ctx *ctx = dev_get_drvdata(dev);
+
+	return sprintf(buf, "%s\n", ctx->message);
+}
+
+/**
+ * message_store() - write a new message via sysfs
+ * @dev: the LCD device
+ * @attr: the LCD message attribute
+ * @buf: the buffer containing the new message
+ * @count: the size of the message in @buf
+ *
+ * Write a new message to display or scroll across the LCD display from sysfs.
+ *
+ * Return: the size of the message on success, else -ERRNO
+ */
+static ssize_t message_store(struct device *dev, struct device_attribute *attr,
+			     const char *buf, size_t count)
+{
+	struct img_ascii_lcd_ctx *ctx = dev_get_drvdata(dev);
+	int err;
+
+	err = img_ascii_lcd_display(ctx, buf, count);
+	return err ?: count;
+}
+
+static DEVICE_ATTR_RW(message);
+
+/**
+ * img_ascii_lcd_probe() - probe an LCD display device
+ * @pdev: the LCD platform device
+ *
+ * Probe an LCD display device, ensuring that we have the required resources in
+ * order to access the LCD & setting up private data as well as sysfs files.
+ *
+ * Return: 0 on success, else -ERRNO
+ */
+static int img_ascii_lcd_probe(struct platform_device *pdev)
+{
+	const struct of_device_id *match;
+	const struct img_ascii_lcd_config *cfg;
+	struct img_ascii_lcd_ctx *ctx;
+	struct resource *res;
+	int err;
+
+	match = of_match_device(img_ascii_lcd_matches, &pdev->dev);
+	if (!match)
+		return -ENODEV;
+
+	cfg = match->data;
+	ctx = devm_kzalloc(&pdev->dev, sizeof(*ctx) + cfg->num_chars,
+			   GFP_KERNEL);
+	if (!ctx)
+		return -ENOMEM;
+
+	if (cfg->external_regmap) {
+		ctx->regmap = syscon_node_to_regmap(pdev->dev.parent->of_node);
+		if (IS_ERR(ctx->regmap))
+			return PTR_ERR(ctx->regmap);
+
+		if (of_property_read_u32(pdev->dev.of_node, "offset",
+					 &ctx->offset))
+			return -EINVAL;
+	} else {
+		res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+		ctx->base = devm_ioremap_resource(&pdev->dev, res);
+		if (IS_ERR(ctx->base))
+			return PTR_ERR(ctx->base);
+	}
+
+	ctx->pdev = pdev;
+	ctx->cfg = cfg;
+	ctx->message = NULL;
+	ctx->scroll_pos = 0;
+	ctx->scroll_rate = HZ / 2;
+
+	/* initialise a timer for scrolling the message */
+	init_timer(&ctx->timer);
+	ctx->timer.function = img_ascii_lcd_scroll;
+	ctx->timer.data = (unsigned long)ctx;
+
+	platform_set_drvdata(pdev, ctx);
+
+	/* display a default message */
+	err = img_ascii_lcd_display(ctx, "Linux " UTS_RELEASE "       ", -1);
+	if (err)
+		goto out_del_timer;
+
+	err = device_create_file(&pdev->dev, &dev_attr_message);
+	if (err)
+		goto out_del_timer;
+
+	return 0;
+out_del_timer:
+	del_timer_sync(&ctx->timer);
+	return err;
+}
+
+/**
+ * img_ascii_lcd_remove() - remove an LCD display device
+ * @pdev: the LCD platform device
+ *
+ * Remove an LCD display device, freeing private resources & ensuring that the
+ * driver stops using the LCD display registers.
+ *
+ * Return: 0
+ */
+static int img_ascii_lcd_remove(struct platform_device *pdev)
+{
+	struct img_ascii_lcd_ctx *ctx = platform_get_drvdata(pdev);
+
+	device_remove_file(&pdev->dev, &dev_attr_message);
+	del_timer_sync(&ctx->timer);
+	return 0;
+}
+
+static struct platform_driver img_ascii_lcd_driver = {
+	.driver = {
+		.name		= "img-ascii-lcd",
+		.of_match_table	= img_ascii_lcd_matches,
+	},
+	.probe	= img_ascii_lcd_probe,
+	.remove	= img_ascii_lcd_remove,
+};
+module_platform_driver(img_ascii_lcd_driver);
-- 
2.9.2

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