fbdev: LCD backlight driver using Atmel PWM driver

This patch adds a platform driver using the ATMEL PWM driver to control a
backlight which requires a PWM signal and optional GPIO signal for discrete
on/off signal.  It has been tested on Favr-32 board from EarthLCD.

The driver is configurable by supplying a struct with the platform data.  See
the include/linux/atmel-pwm-bl.h for details.

The board code for Favr-32 will be submitted to the AVR32 kernel list.

Signed-off-by: Hans-Christian Egtvedt <hans-christian.egtvedt@atmel.com>
Cc: Krzysztof Helt <krzysztof.h1@poczta.fm>
Cc: Haavard Skinnemoen <hskinnemoen@atmel.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 257 insertions, 0 deletions

diff --git a/drivers/video/backlight/Kconfig b/drivers/video/backlight/Kconfig
index b289e197e55d..98d9faf4970d 100644
--- a/drivers/video/backlight/Kconfig
+++ b/drivers/video/backlight/Kconfig
@@ -87,6 +87,18 @@ config BACKLIGHT_ATMEL_LCDC
           If in doubt, it's safe to enable this option; it doesn't kick
           in unless the board's description says it's wired that way.
 
+config BACKLIGHT_ATMEL_PWM
+        tristate "Atmel PWM backlight control"
+        depends on BACKLIGHT_CLASS_DEVICE && ATMEL_PWM
+        default n
+        help
+          Say Y here if you want to use the PWM peripheral in Atmel AT91 and
+          AVR32 devices. This driver will need additional platform data to know
+          which PWM instance to use and how to configure it.
+
+          To compile this driver as a module, choose M here: the module will be
+          called atmel-pwm-bl.
+
 config BACKLIGHT_CORGI
         tristate "Generic (aka Sharp Corgi) Backlight Driver"
         depends on BACKLIGHT_CLASS_DEVICE
diff --git a/drivers/video/backlight/Makefile b/drivers/video/backlight/Makefile
index 7d31c14088aa..d8a08e468cc7 100644
--- a/drivers/video/backlight/Makefile
+++ b/drivers/video/backlight/Makefile
@@ -7,6 +7,7 @@ obj-$(CONFIG_LCD_PLATFORM)	   += platform_lcd.o
 obj-$(CONFIG_LCD_VGG2432A4)        += vgg2432a4.o
 
 obj-$(CONFIG_BACKLIGHT_CLASS_DEVICE) += backlight.o
+obj-$(CONFIG_BACKLIGHT_ATMEL_PWM)    += atmel-pwm-bl.o
 obj-$(CONFIG_BACKLIGHT_CORGI)   += corgi_bl.o
 obj-$(CONFIG_BACKLIGHT_HP680)   += hp680_bl.o
 obj-$(CONFIG_BACKLIGHT_LOCOMO)  += locomolcd.o
diff --git a/drivers/video/backlight/atmel-pwm-bl.c b/drivers/video/backlight/atmel-pwm-bl.c
new file mode 100644
index 000000000000..505c0823a105
--- /dev/null
+++ b/drivers/video/backlight/atmel-pwm-bl.c
@@ -0,0 +1,244 @@
+/*
+ * Copyright (C) 2008 Atmel Corporation
+ *
+ * Backlight driver using Atmel PWM peripheral.
+ *
+ * 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/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/fb.h>
+#include <linux/clk.h>
+#include <linux/gpio.h>
+#include <linux/backlight.h>
+#include <linux/atmel_pwm.h>
+#include <linux/atmel-pwm-bl.h>
+
+struct atmel_pwm_bl {
+        const struct atmel_pwm_bl_platform_data *pdata;
+        struct backlight_device                 *bldev;
+        struct platform_device                  *pdev;
+        struct pwm_channel                      pwmc;
+        int                                     gpio_on;
+};
+
+static int atmel_pwm_bl_set_intensity(struct backlight_device *bd)
+{
+        struct atmel_pwm_bl *pwmbl = bl_get_data(bd);
+        int intensity = bd->props.brightness;
+        int pwm_duty;
+
+        if (bd->props.power != FB_BLANK_UNBLANK)
+                intensity = 0;
+        if (bd->props.fb_blank != FB_BLANK_UNBLANK)
+                intensity = 0;
+
+        if (pwmbl->pdata->pwm_active_low)
+                pwm_duty = pwmbl->pdata->pwm_duty_min + intensity;
+        else
+                pwm_duty = pwmbl->pdata->pwm_duty_max - intensity;
+
+        if (pwm_duty > pwmbl->pdata->pwm_duty_max)
+                pwm_duty = pwmbl->pdata->pwm_duty_max;
+        if (pwm_duty < pwmbl->pdata->pwm_duty_min)
+                pwm_duty = pwmbl->pdata->pwm_duty_min;
+
+        if (!intensity) {
+                if (pwmbl->gpio_on != -1) {
+                        gpio_set_value(pwmbl->gpio_on,
+                                        0 ^ pwmbl->pdata->on_active_low);
+                }
+                pwm_channel_writel(&pwmbl->pwmc, PWM_CUPD, pwm_duty);
+                pwm_channel_disable(&pwmbl->pwmc);
+        } else {
+                pwm_channel_enable(&pwmbl->pwmc);
+                pwm_channel_writel(&pwmbl->pwmc, PWM_CUPD, pwm_duty);
+                if (pwmbl->gpio_on != -1) {
+                        gpio_set_value(pwmbl->gpio_on,
+                                        1 ^ pwmbl->pdata->on_active_low);
+                }
+        }
+
+        return 0;
+}
+
+static int atmel_pwm_bl_get_intensity(struct backlight_device *bd)
+{
+        struct atmel_pwm_bl *pwmbl = bl_get_data(bd);
+        u8 intensity;
+
+        if (pwmbl->pdata->pwm_active_low) {
+                intensity = pwm_channel_readl(&pwmbl->pwmc, PWM_CDTY) -
+                        pwmbl->pdata->pwm_duty_min;
+        } else {
+                intensity = pwmbl->pdata->pwm_duty_max -
+                        pwm_channel_readl(&pwmbl->pwmc, PWM_CDTY);
+        }
+
+        return intensity;
+}
+
+static int atmel_pwm_bl_init_pwm(struct atmel_pwm_bl *pwmbl)
+{
+        unsigned long pwm_rate = pwmbl->pwmc.mck;
+        unsigned long prescale = DIV_ROUND_UP(pwm_rate,
+                        (pwmbl->pdata->pwm_frequency *
+                         pwmbl->pdata->pwm_compare_max)) - 1;
+
+        /*
+         * Prescale must be power of two and maximum 0xf in size because of
+         * hardware limit. PWM speed will be:
+         *      PWM module clock speed / (2 ^ prescale).
+         */
+        prescale = fls(prescale);
+        if (prescale > 0xf)
+                prescale = 0xf;
+
+        pwm_channel_writel(&pwmbl->pwmc, PWM_CMR, prescale);
+        pwm_channel_writel(&pwmbl->pwmc, PWM_CDTY,
+                        pwmbl->pdata->pwm_duty_min +
+                        pwmbl->bldev->props.brightness);
+        pwm_channel_writel(&pwmbl->pwmc, PWM_CPRD,
+                        pwmbl->pdata->pwm_compare_max);
+
+        dev_info(&pwmbl->pdev->dev, "Atmel PWM backlight driver "
+                        "(%lu Hz)\n", pwmbl->pwmc.mck /
+                        pwmbl->pdata->pwm_compare_max /
+                        (1 << prescale));
+
+        return pwm_channel_enable(&pwmbl->pwmc);
+}
+
+static struct backlight_ops atmel_pwm_bl_ops = {
+        .get_brightness = atmel_pwm_bl_get_intensity,
+        .update_status  = atmel_pwm_bl_set_intensity,
+};
+
+static int atmel_pwm_bl_probe(struct platform_device *pdev)
+{
+        const struct atmel_pwm_bl_platform_data *pdata;
+        struct backlight_device *bldev;
+        struct atmel_pwm_bl *pwmbl;
+        int retval;
+
+        pwmbl = kzalloc(sizeof(struct atmel_pwm_bl), GFP_KERNEL);
+        if (!pwmbl)
+                return -ENOMEM;
+
+        pwmbl->pdev = pdev;
+
+        pdata = pdev->dev.platform_data;
+        if (!pdata) {
+                retval = -ENODEV;
+                goto err_free_mem;
+        }
+
+        if (pdata->pwm_compare_max < pdata->pwm_duty_max ||
+                        pdata->pwm_duty_min > pdata->pwm_duty_max ||
+                        pdata->pwm_frequency == 0) {
+                retval = -EINVAL;
+                goto err_free_mem;
+        }
+
+        pwmbl->pdata = pdata;
+        pwmbl->gpio_on = pdata->gpio_on;
+
+        retval = pwm_channel_alloc(pdata->pwm_channel, &pwmbl->pwmc);
+        if (retval)
+                goto err_free_mem;
+
+        if (pwmbl->gpio_on != -1) {
+                retval = gpio_request(pwmbl->gpio_on, "gpio_atmel_pwm_bl");
+                if (retval) {
+                        pwmbl->gpio_on = -1;
+                        goto err_free_pwm;
+                }
+
+                /* Turn display off by defatult. */
+                retval = gpio_direction_output(pwmbl->gpio_on,
+                                0 ^ pdata->on_active_low);
+                if (retval)
+                        goto err_free_gpio;
+        }
+
+        bldev = backlight_device_register("atmel-pwm-bl",
+                        &pdev->dev, pwmbl, &atmel_pwm_bl_ops);
+        if (IS_ERR(bldev)) {
+                retval = PTR_ERR(bldev);
+                goto err_free_gpio;
+        }
+
+        pwmbl->bldev = bldev;
+
+        platform_set_drvdata(pdev, pwmbl);
+
+        /* Power up the backlight by default at middle intesity. */
+        bldev->props.power = FB_BLANK_UNBLANK;
+        bldev->props.max_brightness = pdata->pwm_duty_max - pdata->pwm_duty_min;
+        bldev->props.brightness = bldev->props.max_brightness / 2;
+
+        retval = atmel_pwm_bl_init_pwm(pwmbl);
+        if (retval)
+                goto err_free_bl_dev;
+
+        atmel_pwm_bl_set_intensity(bldev);
+
+        return 0;
+
+err_free_bl_dev:
+        platform_set_drvdata(pdev, NULL);
+        backlight_device_unregister(bldev);
+err_free_gpio:
+        if (pwmbl->gpio_on != -1)
+                gpio_free(pwmbl->gpio_on);
+err_free_pwm:
+        pwm_channel_free(&pwmbl->pwmc);
+err_free_mem:
+        kfree(pwmbl);
+        return retval;
+}
+
+static int __exit atmel_pwm_bl_remove(struct platform_device *pdev)
+{
+        struct atmel_pwm_bl *pwmbl = platform_get_drvdata(pdev);
+
+        if (pwmbl->gpio_on != -1) {
+                gpio_set_value(pwmbl->gpio_on, 0);
+                gpio_free(pwmbl->gpio_on);
+        }
+        pwm_channel_disable(&pwmbl->pwmc);
+        pwm_channel_free(&pwmbl->pwmc);
+        backlight_device_unregister(pwmbl->bldev);
+        platform_set_drvdata(pdev, NULL);
+        kfree(pwmbl);
+
+        return 0;
+}
+
+static struct platform_driver atmel_pwm_bl_driver = {
+        .driver = {
+                .name = "atmel-pwm-bl",
+        },
+        /* REVISIT add suspend() and resume() */
+        .remove = __exit_p(atmel_pwm_bl_remove),
+};
+
+static int __init atmel_pwm_bl_init(void)
+{
+        return platform_driver_probe(&atmel_pwm_bl_driver, atmel_pwm_bl_probe);
+}
+module_init(atmel_pwm_bl_init);
+
+static void __exit atmel_pwm_bl_exit(void)
+{
+        platform_driver_unregister(&atmel_pwm_bl_driver);
+}
+module_exit(atmel_pwm_bl_exit);
+
+MODULE_AUTHOR("Hans-Christian egtvedt <hans-christian.egtvedt@atmel.com>");
+MODULE_DESCRIPTION("Atmel PWM backlight driver");
+MODULE_LICENSE("GPL");