backlight: Add Cirrus EP93xx backlight driver

The EP9307, EP9312, and EP9315 processors include a framebuffer
peripheral. This peripheral has a dedicated pwm output called
BRIGHT that can be used to control the backlight on an LCD.

Signed-off-by: H Hartley Sweeten <[e-mail]>
Signed-off-by: Richard Purdie <[e-mail]>

drivers/video/backlight/Kconfig

···
 	  To compile this driver as a module, choose M here: the module will be
 	  called atmel-pwm-bl.
 
+config BACKLIGHT_EP93XX
+	tristate "Cirrus EP93xx Backlight Driver"
+	depends on FB_EP93XX
+	help
+	  If you have a LCD backlight connected to the BRIGHT output of
+	  the EP93xx, say Y here to enable this driver.
+
+	  To compile this driver as a module, choose M here: the module will
+	  be called ep93xx_bl.
+
 config BACKLIGHT_GENERIC
 	tristate "Generic (aka Sharp Corgi) Backlight Driver"
 	default y

drivers/video/backlight/Makefile

···
 
 obj-$(CONFIG_BACKLIGHT_CLASS_DEVICE) += backlight.o
 obj-$(CONFIG_BACKLIGHT_ATMEL_PWM)    += atmel-pwm-bl.o
+obj-$(CONFIG_BACKLIGHT_EP93XX)	+= ep93xx_bl.o
 obj-$(CONFIG_BACKLIGHT_GENERIC)	+= generic_bl.o
 obj-$(CONFIG_BACKLIGHT_HP700)	+= jornada720_bl.o
 obj-$(CONFIG_BACKLIGHT_HP680)	+= hp680_bl.o

drivers/video/backlight/ep93xx_bl.c

···
+/*
+ * Driver for the Cirrus EP93xx lcd backlight
+ *
+ * Copyright (c) 2010 H Hartley Sweeten <[e-mail]>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This driver controls the pulse width modulated brightness control output,
+ * BRIGHT, on the Cirrus EP9307, EP9312, and EP9315 processors.
+ */
+
+
+#include <linux/platform_device.h>
+#include <linux/io.h>
+#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
+
+struct ep93xxbl {
+	void __iomem *mmio;
+	int brightness;
+};
+
+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);
+
+	ep93xxbl->brightness = brightness;
+
+	return 0;
+}
+
+static int ep93xxbl_update_status(struct backlight_device *bl)
+{
+	int brightness = bl->props.brightness;
+
+	if (bl->props.power != FB_BLANK_UNBLANK ||
+	    bl->props.fb_blank != FB_BLANK_UNBLANK)
+		brightness = 0;
+
+	return ep93xxbl_set(bl, brightness);
+}
+
+static int ep93xxbl_get_brightness(struct backlight_device *bl)
+{
+	struct ep93xxbl *ep93xxbl = bl_get_data(bl);
+
+	return ep93xxbl->brightness;
+}
+
+static const struct backlight_ops ep93xxbl_ops = {
+	.update_status	= ep93xxbl_update_status,
+	.get_brightness	= ep93xxbl_get_brightness,
+};
+
+static int __init ep93xxbl_probe(struct platform_device *dev)
+{
+	struct ep93xxbl *ep93xxbl;
+	struct backlight_device *bl;
+	struct backlight_properties props;
+
+	ep93xxbl = devm_kzalloc(&dev->dev, sizeof(*ep93xxbl), GFP_KERNEL);
+	if (!ep93xxbl)
+		return -ENOMEM;
+
+	/*
+	 * 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.
+	 *
+	 * NOTE: No locking is required; the framebuffer does not touch
+	 * this register.
+	 */
+	ep93xxbl->mmio = EP93XX_RASTER_BRIGHTNESS;
+
+	memset(&props, 0, sizeof(struct backlight_properties));
+	props.max_brightness = EP93XX_MAX_BRIGHT;
+	bl = backlight_device_register(dev->name, &dev->dev, ep93xxbl,
+				       &ep93xxbl_ops, &props);
+	if (IS_ERR(bl))
+		return PTR_ERR(bl);
+
+	bl->props.brightness = EP93XX_DEF_BRIGHT;
+
+	platform_set_drvdata(dev, bl);
+
+	ep93xxbl_update_status(bl);
+
+	return 0;
+}
+
+static int ep93xxbl_remove(struct platform_device *dev)
+{
+	struct backlight_device *bl = platform_get_drvdata(dev);
+
+	backlight_device_unregister(bl);
+	platform_set_drvdata(dev, NULL);
+	return 0;
+}
+
+#ifdef CONFIG_PM
+static int ep93xxbl_suspend(struct platform_device *dev, pm_message_t state)
+{
+	struct backlight_device *bl = platform_get_drvdata(dev);
+
+	return ep93xxbl_set(bl, 0);
+}
+
+static int ep93xxbl_resume(struct platform_device *dev)
+{
+	struct backlight_device *bl = platform_get_drvdata(dev);
+
+	backlight_update_status(bl);
+	return 0;
+}
+#else
+#define ep93xxbl_suspend	NULL
+#define ep93xxbl_resume		NULL
+#endif
+
+static struct platform_driver ep93xxbl_driver = {
+	.driver		= {
+		.name	= "ep93xx-bl",
+		.owner	= THIS_MODULE,
+	},
+	.probe		= ep93xxbl_probe,
+	.remove		= __devexit_p(ep93xxbl_remove),
+	.suspend	= ep93xxbl_suspend,
+	.resume		= ep93xxbl_resume,
+};
+
+static int __init ep93xxbl_init(void)
+{
+	return platform_driver_register(&ep93xxbl_driver);
+}
+module_init(ep93xxbl_init);
+
+static void __exit ep93xxbl_exit(void)
+{
+	platform_driver_unregister(&ep93xxbl_driver);
+}
+module_exit(ep93xxbl_exit);
+
+MODULE_DESCRIPTION("EP93xx Backlight Driver");
+MODULE_AUTHOR("H Hartley Sweeten <[e-mail]>");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:ep93xx-bl");