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 <hsweeten@visionengravers.com>
Signed-off-by: Richard Purdie <rpurdie@linux.intel.com>

3 files changed, 171 insertions, 0 deletions

diff --git a/drivers/video/backlight/Kconfig b/drivers/video/backlight/Kconfig
index 0f7e795f27f8..2d8052182960 100644
--- a/drivers/video/backlight/Kconfig
+++ b/drivers/video/backlight/Kconfig
@@ -142,6 +142,16 @@ config BACKLIGHT_ATMEL_PWM
           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
diff --git a/drivers/video/backlight/Makefile b/drivers/video/backlight/Makefile
index 3cbaacae8f9c..ef610b15fdc6 100644
--- a/drivers/video/backlight/Makefile
+++ b/drivers/video/backlight/Makefile
@@ -14,6 +14,7 @@ obj-$(CONFIG_LCD_TOSA)		   += tosa_lcd.o
 
 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
diff --git a/drivers/video/backlight/ep93xx_bl.c b/drivers/video/backlight/ep93xx_bl.c
new file mode 100644
index 000000000000..b0cc49184803
--- /dev/null
+++ b/drivers/video/backlight/ep93xx_bl.c
@@ -0,0 +1,160 @@
+/*
+ * Driver for the Cirrus EP93xx lcd backlight
+ *
+ * Copyright (c) 2010 H Hartley Sweeten <hsweeten@visionengravers.com>
+ *
+ * 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 <hsweeten@visionengravers.com>");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:ep93xx-bl");