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>hifive-unleashed-5.1
Hans-Christian Egtvedt
Linus Torvalds
parent
2d04a4a72d
commit
3e074058d7
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@ -87,6 +87,18 @@ config BACKLIGHT_ATMEL_LCDC
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If in doubt, it's safe to enable this option; it doesn't kick
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in unless the board's description says it's wired that way.
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config BACKLIGHT_ATMEL_PWM
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tristate "Atmel PWM backlight control"
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depends on BACKLIGHT_CLASS_DEVICE && ATMEL_PWM
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default n
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help
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Say Y here if you want to use the PWM peripheral in Atmel AT91 and
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AVR32 devices. This driver will need additional platform data to know
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which PWM instance to use and how to configure it.
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To compile this driver as a module, choose M here: the module will be
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called atmel-pwm-bl.
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config BACKLIGHT_CORGI
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tristate "Generic (aka Sharp Corgi) Backlight Driver"
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depends on BACKLIGHT_CLASS_DEVICE
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@ -7,6 +7,7 @@ obj-$(CONFIG_LCD_PLATFORM) += platform_lcd.o
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obj-$(CONFIG_LCD_VGG2432A4) += vgg2432a4.o
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obj-$(CONFIG_BACKLIGHT_CLASS_DEVICE) += backlight.o
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obj-$(CONFIG_BACKLIGHT_ATMEL_PWM) += atmel-pwm-bl.o
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obj-$(CONFIG_BACKLIGHT_CORGI) += corgi_bl.o
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obj-$(CONFIG_BACKLIGHT_HP680) += hp680_bl.o
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obj-$(CONFIG_BACKLIGHT_LOCOMO) += locomolcd.o
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@ -0,0 +1,244 @@
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/*
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* Copyright (C) 2008 Atmel Corporation
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*
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* Backlight driver using Atmel PWM peripheral.
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 as published by
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* the Free Software Foundation.
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*/
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#include <linux/init.h>
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/platform_device.h>
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#include <linux/fb.h>
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#include <linux/clk.h>
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#include <linux/gpio.h>
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#include <linux/backlight.h>
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#include <linux/atmel_pwm.h>
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#include <linux/atmel-pwm-bl.h>
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struct atmel_pwm_bl {
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const struct atmel_pwm_bl_platform_data *pdata;
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struct backlight_device *bldev;
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struct platform_device *pdev;
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struct pwm_channel pwmc;
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int gpio_on;
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};
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static int atmel_pwm_bl_set_intensity(struct backlight_device *bd)
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{
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struct atmel_pwm_bl *pwmbl = bl_get_data(bd);
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int intensity = bd->props.brightness;
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int pwm_duty;
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if (bd->props.power != FB_BLANK_UNBLANK)
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intensity = 0;
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if (bd->props.fb_blank != FB_BLANK_UNBLANK)
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intensity = 0;
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if (pwmbl->pdata->pwm_active_low)
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pwm_duty = pwmbl->pdata->pwm_duty_min + intensity;
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else
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pwm_duty = pwmbl->pdata->pwm_duty_max - intensity;
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if (pwm_duty > pwmbl->pdata->pwm_duty_max)
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pwm_duty = pwmbl->pdata->pwm_duty_max;
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if (pwm_duty < pwmbl->pdata->pwm_duty_min)
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pwm_duty = pwmbl->pdata->pwm_duty_min;
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if (!intensity) {
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if (pwmbl->gpio_on != -1) {
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gpio_set_value(pwmbl->gpio_on,
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0 ^ pwmbl->pdata->on_active_low);
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}
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pwm_channel_writel(&pwmbl->pwmc, PWM_CUPD, pwm_duty);
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pwm_channel_disable(&pwmbl->pwmc);
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} else {
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pwm_channel_enable(&pwmbl->pwmc);
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pwm_channel_writel(&pwmbl->pwmc, PWM_CUPD, pwm_duty);
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if (pwmbl->gpio_on != -1) {
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gpio_set_value(pwmbl->gpio_on,
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1 ^ pwmbl->pdata->on_active_low);
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}
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}
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return 0;
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}
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static int atmel_pwm_bl_get_intensity(struct backlight_device *bd)
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{
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struct atmel_pwm_bl *pwmbl = bl_get_data(bd);
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u8 intensity;
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if (pwmbl->pdata->pwm_active_low) {
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intensity = pwm_channel_readl(&pwmbl->pwmc, PWM_CDTY) -
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pwmbl->pdata->pwm_duty_min;
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} else {
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intensity = pwmbl->pdata->pwm_duty_max -
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pwm_channel_readl(&pwmbl->pwmc, PWM_CDTY);
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}
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return intensity;
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}
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static int atmel_pwm_bl_init_pwm(struct atmel_pwm_bl *pwmbl)
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{
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unsigned long pwm_rate = pwmbl->pwmc.mck;
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unsigned long prescale = DIV_ROUND_UP(pwm_rate,
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(pwmbl->pdata->pwm_frequency *
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pwmbl->pdata->pwm_compare_max)) - 1;
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/*
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* Prescale must be power of two and maximum 0xf in size because of
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* hardware limit. PWM speed will be:
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* PWM module clock speed / (2 ^ prescale).
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*/
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prescale = fls(prescale);
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if (prescale > 0xf)
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prescale = 0xf;
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pwm_channel_writel(&pwmbl->pwmc, PWM_CMR, prescale);
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pwm_channel_writel(&pwmbl->pwmc, PWM_CDTY,
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pwmbl->pdata->pwm_duty_min +
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pwmbl->bldev->props.brightness);
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pwm_channel_writel(&pwmbl->pwmc, PWM_CPRD,
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pwmbl->pdata->pwm_compare_max);
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dev_info(&pwmbl->pdev->dev, "Atmel PWM backlight driver "
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"(%lu Hz)\n", pwmbl->pwmc.mck /
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pwmbl->pdata->pwm_compare_max /
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(1 << prescale));
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return pwm_channel_enable(&pwmbl->pwmc);
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}
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static struct backlight_ops atmel_pwm_bl_ops = {
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.get_brightness = atmel_pwm_bl_get_intensity,
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.update_status = atmel_pwm_bl_set_intensity,
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};
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static int atmel_pwm_bl_probe(struct platform_device *pdev)
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{
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const struct atmel_pwm_bl_platform_data *pdata;
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struct backlight_device *bldev;
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struct atmel_pwm_bl *pwmbl;
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int retval;
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pwmbl = kzalloc(sizeof(struct atmel_pwm_bl), GFP_KERNEL);
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if (!pwmbl)
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return -ENOMEM;
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pwmbl->pdev = pdev;
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pdata = pdev->dev.platform_data;
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if (!pdata) {
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retval = -ENODEV;
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goto err_free_mem;
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}
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if (pdata->pwm_compare_max < pdata->pwm_duty_max ||
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pdata->pwm_duty_min > pdata->pwm_duty_max ||
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pdata->pwm_frequency == 0) {
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retval = -EINVAL;
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goto err_free_mem;
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}
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pwmbl->pdata = pdata;
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pwmbl->gpio_on = pdata->gpio_on;
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retval = pwm_channel_alloc(pdata->pwm_channel, &pwmbl->pwmc);
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if (retval)
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goto err_free_mem;
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if (pwmbl->gpio_on != -1) {
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retval = gpio_request(pwmbl->gpio_on, "gpio_atmel_pwm_bl");
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if (retval) {
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pwmbl->gpio_on = -1;
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goto err_free_pwm;
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}
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/* Turn display off by defatult. */
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retval = gpio_direction_output(pwmbl->gpio_on,
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0 ^ pdata->on_active_low);
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if (retval)
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goto err_free_gpio;
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}
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bldev = backlight_device_register("atmel-pwm-bl",
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&pdev->dev, pwmbl, &atmel_pwm_bl_ops);
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if (IS_ERR(bldev)) {
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retval = PTR_ERR(bldev);
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goto err_free_gpio;
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}
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pwmbl->bldev = bldev;
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platform_set_drvdata(pdev, pwmbl);
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/* Power up the backlight by default at middle intesity. */
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bldev->props.power = FB_BLANK_UNBLANK;
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bldev->props.max_brightness = pdata->pwm_duty_max - pdata->pwm_duty_min;
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bldev->props.brightness = bldev->props.max_brightness / 2;
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retval = atmel_pwm_bl_init_pwm(pwmbl);
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if (retval)
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goto err_free_bl_dev;
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atmel_pwm_bl_set_intensity(bldev);
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return 0;
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err_free_bl_dev:
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platform_set_drvdata(pdev, NULL);
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backlight_device_unregister(bldev);
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err_free_gpio:
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if (pwmbl->gpio_on != -1)
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gpio_free(pwmbl->gpio_on);
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err_free_pwm:
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pwm_channel_free(&pwmbl->pwmc);
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err_free_mem:
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kfree(pwmbl);
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return retval;
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}
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static int __exit atmel_pwm_bl_remove(struct platform_device *pdev)
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{
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struct atmel_pwm_bl *pwmbl = platform_get_drvdata(pdev);
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if (pwmbl->gpio_on != -1) {
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gpio_set_value(pwmbl->gpio_on, 0);
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gpio_free(pwmbl->gpio_on);
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}
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pwm_channel_disable(&pwmbl->pwmc);
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pwm_channel_free(&pwmbl->pwmc);
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backlight_device_unregister(pwmbl->bldev);
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platform_set_drvdata(pdev, NULL);
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kfree(pwmbl);
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return 0;
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}
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static struct platform_driver atmel_pwm_bl_driver = {
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.driver = {
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.name = "atmel-pwm-bl",
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},
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/* REVISIT add suspend() and resume() */
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.remove = __exit_p(atmel_pwm_bl_remove),
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};
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static int __init atmel_pwm_bl_init(void)
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{
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return platform_driver_probe(&atmel_pwm_bl_driver, atmel_pwm_bl_probe);
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}
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module_init(atmel_pwm_bl_init);
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static void __exit atmel_pwm_bl_exit(void)
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{
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platform_driver_unregister(&atmel_pwm_bl_driver);
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}
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module_exit(atmel_pwm_bl_exit);
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MODULE_AUTHOR("Hans-Christian egtvedt <hans-christian.egtvedt@atmel.com>");
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MODULE_DESCRIPTION("Atmel PWM backlight driver");
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MODULE_LICENSE("GPL");
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@ -0,0 +1,43 @@
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/*
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* Copyright (C) 2007 Atmel Corporation
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*
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* Driver for the AT32AP700X PS/2 controller (PSIF).
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 as published
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* by the Free Software Foundation.
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*/
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#ifndef __INCLUDE_ATMEL_PWM_BL_H
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#define __INCLUDE_ATMEL_PWM_BL_H
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/**
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* struct atmel_pwm_bl_platform_data
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* @pwm_channel: which PWM channel in the PWM module to use.
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* @pwm_frequency: PWM frequency to generate, the driver will try to be as
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* close as the prescaler allows.
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* @pwm_compare_max: value to use in the PWM channel compare register.
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* @pwm_duty_max: maximum duty cycle value, must be less than or equal to
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* pwm_compare_max.
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* @pwm_duty_min: minimum duty cycle value, must be less than pwm_duty_max.
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* @pwm_active_low: set to one if the low part of the PWM signal increases the
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* brightness of the backlight.
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* @gpio_on: GPIO line to control the backlight on/off, set to -1 if not used.
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* @on_active_low: set to one if the on/off signal is on when GPIO is low.
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*
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* This struct must be added to the platform device in the board code. It is
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* used by the atmel-pwm-bl driver to setup the GPIO to control on/off and the
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* PWM device.
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*/
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struct atmel_pwm_bl_platform_data {
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unsigned int pwm_channel;
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unsigned int pwm_frequency;
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unsigned int pwm_compare_max;
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unsigned int pwm_duty_max;
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unsigned int pwm_duty_min;
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unsigned int pwm_active_low;
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int gpio_on;
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unsigned int on_active_low;
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};
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#endif /* __INCLUDE_ATMEL_PWM_BL_H */
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