ep93xx: Use ioremap for backlight driver

This change “ep93xx: Use ioremap for backlight driver” (commit 0fd1958) in Linux kernel is authored by Ryan Mallon <rmallon [at] gmail.com> on Sun Jan 22 20:31:32 2012 +1100.

Description of "ep93xx: Use ioremap for backlight driver"

The change “ep93xx: Use ioremap for backlight driver” introduces changes as follows.

ep93xx: Use ioremap for backlight driver

The ep93xx backlight driver uses a single register within the
framebuffer's register space. Currently the backlight driver uses a
static IO mapping for the register since the memory cannot be
requested by both drivers.

Convert the static mapping to use ioremap so that we can remove the
dependency on mach/hardware.h. To do so, we need remove the
request_mem_region from both the backlight and framebuffer drivers,
since whichever driver is loaded second will fail with -EBUSY
otherwise.

A proper fix is still required, and a FIXME comment has been added to
both drivers.

Signed-off-by: Ryan Mallon <rmallon@gmail.com>
Suggested-by: Arnd Bergmann <arnd@arndb.de>
Cc: Mika Westerberg <mika.westerberg@iki.fi>
Cc: Richard Purdie <rpurdie@rpsys.net>
Cc: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: H Hartley Sweeten <hsweeten@visionengravers.com>

Linux kernel releases containing commit 0fd1958

The Linux kernel releases containing this commit are as follows.

Linux kernel code changes from "ep93xx: Use ioremap for backlight driver"

There are 53 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 arch/arm/mach-ep93xx/core.c         | 10 ++++++++++
 drivers/video/backlight/ep93xx_bl.c | 25 ++++++++++++++-----------
 drivers/video/ep93xx-fb.c           | 18 +++++++++---------
 3 files changed, 33 insertions(+), 20 deletions(-)
 
diff --git a/arch/arm/mach-ep93xx/core.c b/arch/arm/mach-ep93xx/core.c
index b5c1dae8327f..c73e299b08a5 100644
--- a/arch/arm/mach-ep93xx/core.c
+++ b/arch/arm/mach-ep93xx/core.c
@@ -682,9 +682,19 @@ static struct platform_device ep93xx_fb_device = {
 	.resource		= ep93xx_fb_resource,
 };
 
+/* The backlight use a single register in the framebuffer's register space */
+#define EP93XX_RASTER_REG_BRIGHTNESS 0x20
+
+static struct resource ep93xx_bl_resources[] = {
+	DEFINE_RES_MEM(EP93XX_RASTER_PHYS_BASE +
+		       EP93XX_RASTER_REG_BRIGHTNESS, 0x04),
+};
+
 static struct platform_device ep93xx_bl_device = {
 	.name		= "ep93xx-bl",
 	.id		= -1,
+	.num_resources	= ARRAY_SIZE(ep93xx_bl_resources),
+	.resource	= ep93xx_bl_resources,
 };
 
 /**
diff --git a/drivers/video/backlight/ep93xx_bl.c b/drivers/video/backlight/ep93xx_bl.c
index b62b8b9063b5..08214e1f0958 100644
--- a/drivers/video/backlight/ep93xx_bl.c
+++ b/drivers/video/backlight/ep93xx_bl.c
@@ -17,11 +17,6 @@
 #include <linux/fb.h>
 #include <linux/backlight.h>
 
-#include <mach/hardware.h>
-
-#define EP93XX_RASTER_REG(x)		(EP93XX_RASTER_BASE + (x))
-#define EP93XX_RASTER_BRIGHTNESS	EP93XX_RASTER_REG(0x20)
-
 #define EP93XX_MAX_COUNT		255
 #define EP93XX_MAX_BRIGHT		255
 #define EP93XX_DEF_BRIGHT		128
@@ -35,7 +30,7 @@ static int ep93xxbl_set(struct backlight_device *bl, int brightness)
 {
 	struct ep93xxbl *ep93xxbl = bl_get_data(bl);
 
-	__raw_writel((brightness << 8) | EP93XX_MAX_COUNT, ep93xxbl->mmio);
+	writel((brightness << 8) | EP93XX_MAX_COUNT, ep93xxbl->mmio);
 
 	ep93xxbl->brightness = brightness;
 
@@ -70,21 +65,29 @@ static int __init ep93xxbl_probe(struct platform_device *dev)
 	struct ep93xxbl *ep93xxbl;
 	struct backlight_device *bl;
 	struct backlight_properties props;
+	struct resource *res;
 
 	ep93xxbl = devm_kzalloc(&dev->dev, sizeof(*ep93xxbl), GFP_KERNEL);
 	if (!ep93xxbl)
 		return -ENOMEM;
 
+	res = platform_get_resource(dev, IORESOURCE_MEM, 0);
+	if (!res)
+		return -ENXIO;
+
 	/*
-	 * This register is located in the range already ioremap'ed by
-	 * the framebuffer driver.  A MFD driver seems a bit of overkill
-	 * to handle this so use the static I/O mapping; this address
-	 * is already virtual.
+	 * FIXME - We don't do a request_mem_region here because we are
+	 * sharing the register space with the framebuffer driver (see
+	 * drivers/video/ep93xx-fb.c) and doing so will cause the second
+	 * loaded driver to return -EBUSY.
 	 *
 	 * NOTE: No locking is required; the framebuffer does not touch
 	 * this register.
 	 */
-	ep93xxbl->mmio = EP93XX_RASTER_BRIGHTNESS;
+	ep93xxbl->mmio = devm_ioremap(&dev->dev, res->start,
+				      resource_size(res));
+	if (!ep93xxbl->mmio)
+		return -ENXIO;
 
 	memset(&props, 0, sizeof(struct backlight_properties));
 	props.type = BACKLIGHT_RAW;
diff --git a/drivers/video/ep93xx-fb.c b/drivers/video/ep93xx-fb.c
index 2e830ec52a5a..f8babbeee275 100644
--- a/drivers/video/ep93xx-fb.c
+++ b/drivers/video/ep93xx-fb.c
@@ -519,12 +519,15 @@ static int __devinit ep93xxfb_probe(struct platform_device *pdev)
 		goto failed;
 	}
 
-	res = request_mem_region(res->start, resource_size(res), pdev->name);
-	if (!res) {
-		err = -EBUSY;
-		goto failed;
-	}
-
+	/*
+	 * FIXME - We don't do a request_mem_region here because we are
+	 * sharing the register space with the backlight driver (see
+	 * drivers/video/backlight/ep93xx_bl.c) and doing so will cause
+	 * the second loaded driver to return -EBUSY.
+	 *
+	 * NOTE: No locking is required; the backlight does not touch
+	 * any of the framebuffer registers.
+	 */
 	fbi->res = res;
 	fbi->mmio_base = ioremap(res->start, resource_size(res));
 	if (!fbi->mmio_base) {
@@ -586,8 +589,6 @@ static int __devinit ep93xxfb_probe(struct platform_device *pdev)
 		clk_put(fbi->clk);
 	if (fbi->mmio_base)
 		iounmap(fbi->mmio_base);
-	if (fbi->res)
-		release_mem_region(fbi->res->start, resource_size(fbi->res));
 	ep93xxfb_dealloc_videomem(info);
 	if (&info->cmap)
 		fb_dealloc_cmap(&info->cmap);
@@ -608,7 +609,6 @@ static int __devexit ep93xxfb_remove(struct platform_device *pdev)
 	clk_disable(fbi->clk);
 	clk_put(fbi->clk);
 	iounmap(fbi->mmio_base);
-	release_mem_region(fbi->res->start, resource_size(fbi->res));
 	ep93xxfb_dealloc_videomem(info);
 	fb_dealloc_cmap(&info->cmap);
 

The commit for this change in Linux stable tree is 0fd1958 (patch).

Last modified: 2020/02/10