[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>

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.

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

drivers/video/backlight/pwm_bl.c

+/*
+ * 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");

include/linux/pwm_backlight.h

+/*
+ * Generic PWM backlight driver data - see drivers/video/backlight/pwm_bl.c
+ */
+#ifndef __LINUX_PWM_BACKLIGHT_H
+#define __LINUX_PWM_BACKLIGHT_H
+
+struct platform_pwm_backlight_data {
+	int pwm_id;
+	unsigned int max_brightness;
+	unsigned int dft_brightness;
+	unsigned int pwm_period_ns;
+};
+
+#endif