[ARM] pxa: add generic PWM backlight driver

Patch mostly from Eric Miao, with minor edits by rmk to convert
Eric's driver to a generic PWM-based backlight driver.

Signed-off-by: eric miao <eric.miao@marvell.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

3 files changed, 168 insertions, 0 deletions

diff --git a/drivers/video/backlight/Kconfig b/drivers/video/backlight/Kconfig
index dcd8073c2369..30bf7f2f1635 100644
--- a/drivers/video/backlight/Kconfig
+++ b/drivers/video/backlight/Kconfig
@@ -112,3 +112,10 @@ config BACKLIGHT_CARILLO_RANCH
         help
           If you have a Intel LE80578 (Carillo Ranch) say Y to enable the
           backlight driver.
+
+config BACKLIGHT_PWM
+        tristate "Generic PWM based Backlight Driver"
+        depends on BACKLIGHT_CLASS_DEVICE && HAVE_PWM
+        help
+          If you have a LCD backlight adjustable by PWM, say Y to enable
+          this driver.
diff --git a/drivers/video/backlight/Makefile b/drivers/video/backlight/Makefile
index 33f6c7cecc73..b51a7cd12500 100644
--- a/drivers/video/backlight/Makefile
+++ b/drivers/video/backlight/Makefile
@@ -10,3 +10,4 @@ obj-$(CONFIG_BACKLIGHT_LOCOMO)	+= locomolcd.o
 obj-$(CONFIG_BACKLIGHT_OMAP1)   += omap1_bl.o
 obj-$(CONFIG_BACKLIGHT_PROGEAR) += progear_bl.o
 obj-$(CONFIG_BACKLIGHT_CARILLO_RANCH) += cr_bllcd.o
+obj-$(CONFIG_BACKLIGHT_PWM)     += pwm_bl.o
diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
new file mode 100644
index 000000000000..9637f5e08cb6
--- /dev/null
+++ b/drivers/video/backlight/pwm_bl.c
@@ -0,0 +1,160 @@
+/*
+ * linux/drivers/video/backlight/pwm_bl.c
+ *
+ * simple PWM based backlight control, board code has to setup
+ * 1) pin configuration so PWM waveforms can output
+ * 2) platform_data casts to the PWM id (0/1/2/3 on PXA)
+ *
+ * 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.
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/platform_device.h>
+#include <linux/fb.h>
+#include <linux/backlight.h>
+#include <linux/err.h>
+#include <linux/pwm.h>
+#include <linux/pwm_backlight.h>
+
+struct pwm_bl_data {
+        struct pwm_device       *pwm;
+        unsigned int            period;
+};
+
+static int pwm_backlight_update_status(struct backlight_device *bl)
+{
+        struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev);
+        int brightness = bl->props.brightness;
+        int max = bl->props.max_brightness;
+
+        if (bl->props.power != FB_BLANK_UNBLANK)
+                brightness = 0;
+
+        if (bl->props.fb_blank != FB_BLANK_UNBLANK)
+                brightness = 0;
+
+        if (brightness == 0) {
+                pwm_config(pb->pwm, 0, pb->period);
+                pwm_disable(pb->pwm);
+        } else {
+                pwm_config(pb->pwm, brightness * pb->period / max, pb->period);
+                pwm_enable(pb->pwm);
+        }
+        return 0;
+}
+
+static int pwm_backlight_get_brightness(struct backlight_device *bl)
+{
+        return bl->props.brightness;
+}
+
+static struct backlight_ops pwm_backlight_ops = {
+        .update_status  = pwm_backlight_update_status,
+        .get_brightness = pwm_backlight_get_brightness,
+};
+
+static int pwm_backlight_probe(struct platform_device *pdev)
+{
+        struct platform_pwm_backlight_data *data = pdev->dev.platform_data;
+        struct backlight_device *bl;
+        struct pwm_bl_data *pb;
+
+        if (!data)
+                return -EINVAL;
+
+        pb = kzalloc(sizeof(*pb), GFP_KERNEL);
+        if (!pb)
+                return -ENOMEM;
+
+        pb->period = data->pwm_period_ns;
+
+        pb->pwm = pwm_request(data->pwm_id, "backlight");
+        if (pb->pwm == NULL) {
+                dev_err(&pdev->dev, "unable to request PWM for backlight\n");
+                kfree(pb);
+                return -EBUSY;
+        }
+
+        bl = backlight_device_register(pdev->name, &pdev->dev,
+                        pb, &pwm_backlight_ops);
+        if (IS_ERR(bl)) {
+                dev_err(&pdev->dev, "failed to register backlight\n");
+                pwm_free(pb->pwm);
+                kfree(pb);
+                return PTR_ERR(bl);
+        }
+
+        bl->props.max_brightness = data->max_brightness;
+        bl->props.brightness = data->dft_brightness;
+        backlight_update_status(bl);
+
+        platform_set_drvdata(pdev, bl);
+        return 0;
+}
+
+static int pwm_backlight_remove(struct platform_device *pdev)
+{
+        struct backlight_device *bl = platform_get_drvdata(pdev);
+        struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev);
+
+        backlight_device_unregister(bl);
+        pwm_config(pb->pwm, 0, pb->period);
+        pwm_disable(pb->pwm);
+        pwm_free(pb->pwm);
+        kfree(pb);
+        return 0;
+}
+
+#ifdef CONFIG_PM
+static int pwm_backlight_suspend(struct platform_device *pdev,
+                                 pm_message_t state)
+{
+        struct backlight_device *bl = platform_get_drvdata(pdev);
+        struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev);
+
+        pwm_config(pb->pwm, 0, pb->period);
+        pwm_disable(pb->pwm);
+        return 0;
+}
+
+static int pwm_backlight_resume(struct platform_device *pdev)
+{
+        struct backlight_device *bl = platform_get_drvdata(pdev);
+
+        backlight_update_status(bl);
+        return 0;
+}
+#else
+#define pwm_backlight_suspend   NULL
+#define pwm_backlight_resume    NULL
+#endif
+
+static struct platform_driver pwm_backlight_driver = {
+        .driver         = {
+                .name   = "pwm-backlight",
+                .owner  = THIS_MODULE,
+        },
+        .probe          = pwm_backlight_probe,
+        .remove         = pwm_backlight_remove,
+        .suspend        = pwm_backlight_suspend,
+        .resume         = pwm_backlight_resume,
+};
+
+static int __init pwm_backlight_init(void)
+{
+        return platform_driver_register(&pwm_backlight_driver);
+}
+module_init(pwm_backlight_init);
+
+static void __exit pwm_backlight_exit(void)
+{
+        platform_driver_unregister(&pwm_backlight_driver);
+}
+module_exit(pwm_backlight_exit);
+
+MODULE_DESCRIPTION("PWM based Backlight Driver");
+MODULE_LICENSE("GPL");