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.
Signed-off-by: Hans-Christian Egtvedt <[email protected]>
---
The board code for Favr-32 will be submitted to the AVR32 kernel list.
drivers/video/backlight/Kconfig | 12 ++
drivers/video/backlight/Makefile | 1 +
drivers/video/backlight/atmel-pwm-bl.c | 244 ++++++++++++++++++++++++++++++++
include/linux/atmel-pwm-bl.h | 43 ++++++
4 files changed, 300 insertions(+), 0 deletions(-)
create mode 100644 drivers/video/backlight/atmel-pwm-bl.c
create mode 100644 include/linux/atmel-pwm-bl.h
diff --git a/drivers/video/backlight/Kconfig b/drivers/video/backlight/Kconfig
index dcd8073..7557caa 100644
--- a/drivers/video/backlight/Kconfig
+++ b/drivers/video/backlight/Kconfig
@@ -63,6 +63,18 @@ 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 33f6c7c..62d022a 100644
--- a/drivers/video/backlight/Makefile
+++ b/drivers/video/backlight/Makefile
@@ -4,6 +4,7 @@ obj-$(CONFIG_LCD_CLASS_DEVICE) += lcd.o
obj-$(CONFIG_LCD_LTV350QV) += ltv350qv.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 0000000..505c082
--- /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 <[email protected]>");
+MODULE_DESCRIPTION("Atmel PWM backlight driver");
+MODULE_LICENSE("GPL");
diff --git a/include/linux/atmel-pwm-bl.h b/include/linux/atmel-pwm-bl.h
new file mode 100644
index 0000000..0153a47
--- /dev/null
+++ b/include/linux/atmel-pwm-bl.h
@@ -0,0 +1,43 @@
+/*
+ * Copyright (C) 2007 Atmel Corporation
+ *
+ * Driver for the AT32AP700X PS/2 controller (PSIF).
+ *
+ * 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.
+ */
+
+#ifndef __INCLUDE_ATMEL_PWM_BL_H
+#define __INCLUDE_ATMEL_PWM_BL_H
+
+/**
+ * struct atmel_pwm_bl_platform_data
+ * @pwm_channel: which PWM channel in the PWM module to use.
+ * @pwm_frequency: PWM frequency to generate, the driver will try to be as
+ * close as the prescaler allows.
+ * @pwm_compare_max: value to use in the PWM channel compare register.
+ * @pwm_duty_max: maximum duty cycle value, must be less than or equal to
+ * pwm_compare_max.
+ * @pwm_duty_min: minimum duty cycle value, must be less than pwm_duty_max.
+ * @pwm_active_low: set to one if the low part of the PWM signal increases the
+ * brightness of the backlight.
+ * @gpio_on: GPIO line to control the backlight on/off, set to -1 if not used.
+ * @on_active_low: set to one if the on/off signal is on when GPIO is low.
+ *
+ * This struct must be added to the platform device in the board code. It is
+ * used by the atmel-pwm-bl driver to setup the GPIO to control on/off and the
+ * PWM device.
+ */
+struct atmel_pwm_bl_platform_data {
+ unsigned int pwm_channel;
+ unsigned int pwm_frequency;
+ unsigned int pwm_compare_max;
+ unsigned int pwm_duty_max;
+ unsigned int pwm_duty_min;
+ unsigned int pwm_active_low;
+ int gpio_on;
+ unsigned int on_active_low;
+};
+
+#endif /* __INCLUDE_ATMEL_PWM_BL_H */
--
1.5.4.3
On Wed, 9 Jul 2008 15:08:06 +0200 Hans-Christian Egtvedt <[email protected]> wrote:
> + if (bd->props.power != FB_BLANK_UNBLANK)
> + intensity = 0;
> + if (bd->props.fb_blank != FB_BLANK_UNBLANK)
> + intensity = 0;
hm, is that correct? It is strange that two different fields can validly
be compared with the same enumeration like this.
On Fri, 2008-07-11 at 12:17 -0700, Andrew Morton wrote:
> On Wed, 9 Jul 2008 15:08:06 +0200 Hans-Christian Egtvedt <[email protected]> wrote:
>
> > + if (bd->props.power != FB_BLANK_UNBLANK)
> > + intensity = 0;
> > + if (bd->props.fb_blank != FB_BLANK_UNBLANK)
> > + intensity = 0;
>
> hm, is that correct? It is strange that two different fields can validly
> be compared with the same enumeration like this.
>
I also found it a bit weird having two fields indicating the same, but
the header file has the following documentation:
/* Current FB Power mode (0: full on, 1..3: power saving
modes; 4: full off), see FB_BLANK_XXX */
int power;
/* FB Blanking active? (values as for power) */
int fb_blank;
So, AFAIK, my assumptions are correct to get proper blanking?
--
With kind regards,
Hans-Christian Egtvedt, Applications Engineer