linux/drivers/video/backlight/pwm_bl.c

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/*
* 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 being correctly configured
*
* 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>
include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h percpu.h is included by sched.h and module.h and thus ends up being included when building most .c files. percpu.h includes slab.h which in turn includes gfp.h making everything defined by the two files universally available and complicating inclusion dependencies. percpu.h -> slab.h dependency is about to be removed. Prepare for this change by updating users of gfp and slab facilities include those headers directly instead of assuming availability. As this conversion needs to touch large number of source files, the following script is used as the basis of conversion. http://userweb.kernel.org/~tj/misc/slabh-sweep.py The script does the followings. * Scan files for gfp and slab usages and update includes such that only the necessary includes are there. ie. if only gfp is used, gfp.h, if slab is used, slab.h. * When the script inserts a new include, it looks at the include blocks and try to put the new include such that its order conforms to its surrounding. It's put in the include block which contains core kernel includes, in the same order that the rest are ordered - alphabetical, Christmas tree, rev-Xmas-tree or at the end if there doesn't seem to be any matching order. * If the script can't find a place to put a new include (mostly because the file doesn't have fitting include block), it prints out an error message indicating which .h file needs to be added to the file. The conversion was done in the following steps. 1. The initial automatic conversion of all .c files updated slightly over 4000 files, deleting around 700 includes and adding ~480 gfp.h and ~3000 slab.h inclusions. The script emitted errors for ~400 files. 2. Each error was manually checked. Some didn't need the inclusion, some needed manual addition while adding it to implementation .h or embedding .c file was more appropriate for others. This step added inclusions to around 150 files. 3. The script was run again and the output was compared to the edits from #2 to make sure no file was left behind. 4. Several build tests were done and a couple of problems were fixed. e.g. lib/decompress_*.c used malloc/free() wrappers around slab APIs requiring slab.h to be added manually. 5. The script was run on all .h files but without automatically editing them as sprinkling gfp.h and slab.h inclusions around .h files could easily lead to inclusion dependency hell. Most gfp.h inclusion directives were ignored as stuff from gfp.h was usually wildly available and often used in preprocessor macros. Each slab.h inclusion directive was examined and added manually as necessary. 6. percpu.h was updated not to include slab.h. 7. Build test were done on the following configurations and failures were fixed. CONFIG_GCOV_KERNEL was turned off for all tests (as my distributed build env didn't work with gcov compiles) and a few more options had to be turned off depending on archs to make things build (like ipr on powerpc/64 which failed due to missing writeq). * x86 and x86_64 UP and SMP allmodconfig and a custom test config. * powerpc and powerpc64 SMP allmodconfig * sparc and sparc64 SMP allmodconfig * ia64 SMP allmodconfig * s390 SMP allmodconfig * alpha SMP allmodconfig * um on x86_64 SMP allmodconfig 8. percpu.h modifications were reverted so that it could be applied as a separate patch and serve as bisection point. Given the fact that I had only a couple of failures from tests on step 6, I'm fairly confident about the coverage of this conversion patch. If there is a breakage, it's likely to be something in one of the arch headers which should be easily discoverable easily on most builds of the specific arch. Signed-off-by: Tejun Heo <tj@kernel.org> Guess-its-ok-by: Christoph Lameter <cl@linux-foundation.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
2010-03-24 08:04:11 +00:00
#include <linux/slab.h>
struct pwm_bl_data {
struct pwm_device *pwm;
struct device *dev;
unsigned int period;
backlight: add low threshold to pwm backlight The intensity of the backlight can be varied from a range of max_brightness to zero. Though most, if not all the pwm based backlight devices start flickering at lower brightness value. And also for each device there exists a brightness value below which the backlight appears to be turned off though the value is not equal to zero. If the range of brightness for a device is from zero to max_brightness. A graph is plotted for brightness Vs intensity for the pwm based backlight device has to be a linear graph. intensity | / | / | / |/ --------- 0 max_brightness But pratically on measuring the above we note that the intensity of backlight goes to zero(OFF) when the value in not zero almost nearing to zero(some x%). so the graph looks like intensity | / | / | / | | ------------ 0 x max_brightness In order to overcome this drawback knowing this x% i.e nothing but the low threshold beyond which the backlight is off and will have no effect, the brightness value is being offset by the low threshold value(retaining the linearity of the graph). Now the graph becomes intensity | / | / | / | / ------------- 0 max_brightness With this for each and every digit increment in the brightness from zero there is a change in the intensity of backlight. Devices having this behaviour can set the low threshold brightness(lth_brightness) and pass the same as platform data else can have it as zero. [akpm@linux-foundation.org: coding-style fixes] Signed-off-by: Arun Murthy <arun.murthy@stericsson.com> Acked-by: Linus Walleij <linus.walleij@stericsson.com> Acked-by: Richard Purdie <rpurdie@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2010-11-11 22:05:28 +00:00
unsigned int lth_brightness;
int (*notify)(struct device *,
int brightness);
};
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 (pb->notify)
brightness = pb->notify(pb->dev, brightness);
if (brightness == 0) {
pwm_config(pb->pwm, 0, pb->period);
pwm_disable(pb->pwm);
} else {
backlight: add low threshold to pwm backlight The intensity of the backlight can be varied from a range of max_brightness to zero. Though most, if not all the pwm based backlight devices start flickering at lower brightness value. And also for each device there exists a brightness value below which the backlight appears to be turned off though the value is not equal to zero. If the range of brightness for a device is from zero to max_brightness. A graph is plotted for brightness Vs intensity for the pwm based backlight device has to be a linear graph. intensity | / | / | / |/ --------- 0 max_brightness But pratically on measuring the above we note that the intensity of backlight goes to zero(OFF) when the value in not zero almost nearing to zero(some x%). so the graph looks like intensity | / | / | / | | ------------ 0 x max_brightness In order to overcome this drawback knowing this x% i.e nothing but the low threshold beyond which the backlight is off and will have no effect, the brightness value is being offset by the low threshold value(retaining the linearity of the graph). Now the graph becomes intensity | / | / | / | / ------------- 0 max_brightness With this for each and every digit increment in the brightness from zero there is a change in the intensity of backlight. Devices having this behaviour can set the low threshold brightness(lth_brightness) and pass the same as platform data else can have it as zero. [akpm@linux-foundation.org: coding-style fixes] Signed-off-by: Arun Murthy <arun.murthy@stericsson.com> Acked-by: Linus Walleij <linus.walleij@stericsson.com> Acked-by: Richard Purdie <rpurdie@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2010-11-11 22:05:28 +00:00
brightness = pb->lth_brightness +
(brightness * (pb->period - pb->lth_brightness) / max);
pwm_config(pb->pwm, brightness, pb->period);
pwm_enable(pb->pwm);
}
return 0;
}
static int pwm_backlight_get_brightness(struct backlight_device *bl)
{
return bl->props.brightness;
}
static const 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 backlight_properties props;
struct platform_pwm_backlight_data *data = pdev->dev.platform_data;
struct backlight_device *bl;
struct pwm_bl_data *pb;
int ret;
if (!data) {
dev_err(&pdev->dev, "failed to find platform data\n");
return -EINVAL;
}
if (data->init) {
ret = data->init(&pdev->dev);
if (ret < 0)
return ret;
}
pb = kzalloc(sizeof(*pb), GFP_KERNEL);
if (!pb) {
dev_err(&pdev->dev, "no memory for state\n");
ret = -ENOMEM;
goto err_alloc;
}
pb->period = data->pwm_period_ns;
pb->notify = data->notify;
backlight: add low threshold to pwm backlight The intensity of the backlight can be varied from a range of max_brightness to zero. Though most, if not all the pwm based backlight devices start flickering at lower brightness value. And also for each device there exists a brightness value below which the backlight appears to be turned off though the value is not equal to zero. If the range of brightness for a device is from zero to max_brightness. A graph is plotted for brightness Vs intensity for the pwm based backlight device has to be a linear graph. intensity | / | / | / |/ --------- 0 max_brightness But pratically on measuring the above we note that the intensity of backlight goes to zero(OFF) when the value in not zero almost nearing to zero(some x%). so the graph looks like intensity | / | / | / | | ------------ 0 x max_brightness In order to overcome this drawback knowing this x% i.e nothing but the low threshold beyond which the backlight is off and will have no effect, the brightness value is being offset by the low threshold value(retaining the linearity of the graph). Now the graph becomes intensity | / | / | / | / ------------- 0 max_brightness With this for each and every digit increment in the brightness from zero there is a change in the intensity of backlight. Devices having this behaviour can set the low threshold brightness(lth_brightness) and pass the same as platform data else can have it as zero. [akpm@linux-foundation.org: coding-style fixes] Signed-off-by: Arun Murthy <arun.murthy@stericsson.com> Acked-by: Linus Walleij <linus.walleij@stericsson.com> Acked-by: Richard Purdie <rpurdie@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2010-11-11 22:05:28 +00:00
pb->lth_brightness = data->lth_brightness *
(data->pwm_period_ns / data->max_brightness);
pb->dev = &pdev->dev;
pb->pwm = pwm_request(data->pwm_id, "backlight");
if (IS_ERR(pb->pwm)) {
dev_err(&pdev->dev, "unable to request PWM for backlight\n");
ret = PTR_ERR(pb->pwm);
goto err_pwm;
} else
dev_dbg(&pdev->dev, "got pwm for backlight\n");
memset(&props, 0, sizeof(struct backlight_properties));
props.max_brightness = data->max_brightness;
bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, pb,
&pwm_backlight_ops, &props);
if (IS_ERR(bl)) {
dev_err(&pdev->dev, "failed to register backlight\n");
ret = PTR_ERR(bl);
goto err_bl;
}
bl->props.brightness = data->dft_brightness;
backlight_update_status(bl);
platform_set_drvdata(pdev, bl);
return 0;
err_bl:
pwm_free(pb->pwm);
err_pwm:
kfree(pb);
err_alloc:
if (data->exit)
data->exit(&pdev->dev);
return ret;
}
static int pwm_backlight_remove(struct platform_device *pdev)
{
struct platform_pwm_backlight_data *data = pdev->dev.platform_data;
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);
if (data->exit)
data->exit(&pdev->dev);
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);
if (pb->notify)
pb->notify(pb->dev, 0);
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");
MODULE_ALIAS("platform:pwm-backlight");