lkml.org 
[lkml]   [2013]   [Mar]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 1/1 v2] pwm_bl: Add support for backlight enable GPIO
On 03/05/2013 01:43 PM, Andrew Chew wrote:
> The backlight enable GPIO is specified in the device tree node for
> backlight.
>
> Signed-off-by: Andrew Chew <achew@nvidia.com>
> ---
> I decided to go ahead with disabling/enabling the backlight via GPIO as
> needed. Note that I named the new functions pwm_backlight_enable() and
> pwm_backlight_disable() (instead of something more gpio-specific) because
> I thought it would be convenient to have a generic hook for when someone
> wants to add yet more stuff to be done on enable/disable.
>
> I tested this by going into /sys/class/backlight/backlight.n and manually
> adjusting the brightness, and checked the gpio state to see that it had
> the appropriate value.
>
> .../bindings/video/backlight/pwm-backlight.txt | 2 +
> drivers/video/backlight/pwm_bl.c | 50 ++++++++++++++++++--
> include/linux/pwm_backlight.h | 2 +
> 3 files changed, 50 insertions(+), 4 deletions(-)
>
> diff --git a/Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt b/Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt
> index 1e4fc72..1ed4f0f 100644
> --- a/Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt
> +++ b/Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt
> @@ -14,6 +14,8 @@ Required properties:
> Optional properties:
> - pwm-names: a list of names for the PWM devices specified in the
> "pwms" property (see PWM binding[0])
> + - enable-gpio: a GPIO that needs to be used to enable the backlight
> + - enable-gpio-active-high: polarity of GPIO is active high (default is low)
>
> [0]: Documentation/devicetree/bindings/pwm/pwm.txt
>
> diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
> index 069983c..7dd426e 100644
> --- a/drivers/video/backlight/pwm_bl.c
> +++ b/drivers/video/backlight/pwm_bl.c
> @@ -20,10 +20,13 @@
> #include <linux/pwm.h>
> #include <linux/pwm_backlight.h>
> #include <linux/slab.h>
> +#include <linux/of_gpio.h>
>
> struct pwm_bl_data {
> struct pwm_device *pwm;
> struct device *dev;
> + int enable_gpio;
> + unsigned int enable_gpio_flags;
> unsigned int period;
> unsigned int lth_brightness;
> unsigned int *levels;
> @@ -35,6 +38,20 @@ struct pwm_bl_data {
> void (*exit)(struct device *);
> };
>
> +static void pwm_backlight_enable(struct pwm_bl_data *pb)
> +{
> + if (gpio_is_valid(pb->enable_gpio))
> + gpio_set_value(pb->enable_gpio,
> + pb->enable_gpio_flags & GPIOF_INIT_HIGH ? 1 : 0);
> +}
> +
> +static void pwm_backlight_disable(struct pwm_bl_data *pb)
> +{
> + if (gpio_is_valid(pb->enable_gpio))
> + gpio_set_value(pb->enable_gpio,
> + pb->enable_gpio_flags & GPIOF_INIT_HIGH ? 0 : 1);
> +}
> +
> static int pwm_backlight_update_status(struct backlight_device *bl)
> {
> struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev);
> @@ -53,6 +70,7 @@ static int pwm_backlight_update_status(struct backlight_device *bl)
> if (brightness == 0) {
> pwm_config(pb->pwm, 0, pb->period);
> pwm_disable(pb->pwm);
> + pwm_backlight_disable(pb);

Maybe move the call to pwm_backlight_disable() before pwm_disable() to
have a correctly nested power sequence?

Actually every call to pwm_disable/enable is near
pwm_backlight_disable/enable, so you might as well want to call
pwm_disable/enable within pwm_backlight_enable/disable to make the code
more bullet-proof.

> } else {
> int duty_cycle;
>
> @@ -67,6 +85,7 @@ static int pwm_backlight_update_status(struct backlight_device *bl)
> (duty_cycle * (pb->period - pb->lth_brightness) / max);
> pwm_config(pb->pwm, duty_cycle, pb->period);
> pwm_enable(pb->pwm);
> + pwm_backlight_enable(pb);
> }
>
> if (pb->notify_after)
> @@ -146,10 +165,15 @@ static int pwm_backlight_parse_dt(struct device *dev,
> }
>
> /*
> - * TODO: Most users of this driver use a number of GPIOs to control
> - * backlight power. Support for specifying these needs to be
> - * added.
> + * If "enable-gpio" is present, use that GPIO to enable the backlight.
> + * The presence (or not) of "enable-gpio-active-high" will determine
> + * the value of the GPIO.
> */
> + data->enable_gpio = of_get_named_gpio(node, "enable-gpio", 0);
> + if (of_property_read_bool(node, "enable-gpio-active-high"))
> + data->enable_gpio_flags = GPIOF_OUT_INIT_HIGH;
> + else
> + data->enable_gpio_flags = GPIOF_OUT_INIT_LOW;
>
> return 0;
> }
> @@ -207,12 +231,23 @@ static int pwm_backlight_probe(struct platform_device *pdev)
> } else
> max = data->max_brightness;
>
> + pb->enable_gpio = data->enable_gpio;
> + pb->enable_gpio_flags = data->enable_gpio_flags;
> pb->notify = data->notify;
> pb->notify_after = data->notify_after;
> pb->check_fb = data->check_fb;
> pb->exit = data->exit;
> pb->dev = &pdev->dev;
>
> + if (gpio_is_valid(pb->enable_gpio)) {
> + ret = gpio_request_one(pb->enable_gpio,
> + GPIOF_DIR_OUT | pb->enable_gpio_flags, "bl_en");

I would not assume that the backlight should be enabled here. Maybe you
can use gpio_request() and gpio_set_output() to leave the output value
unchanged - the backlight framework will call update_status() anyway,
which will set the GPIO value accordingly.

> + if (ret) {
> + dev_err(&pdev->dev, "failed to allocate bl_en gpio");
> + goto err_alloc;
> + }
> + }
> +
> pb->pwm = devm_pwm_get(&pdev->dev, NULL);
> if (IS_ERR(pb->pwm)) {
> dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n");
> @@ -221,7 +256,7 @@ static int pwm_backlight_probe(struct platform_device *pdev)
> if (IS_ERR(pb->pwm)) {
> dev_err(&pdev->dev, "unable to request legacy PWM\n");
> ret = PTR_ERR(pb->pwm);
> - goto err_alloc;
> + goto err_gpio;
> }
> }
>
> @@ -255,6 +290,9 @@ static int pwm_backlight_probe(struct platform_device *pdev)
> platform_set_drvdata(pdev, bl);
> return 0;
>
> +err_gpio:
> + if (gpio_is_valid(data->enable_gpio))
> + gpio_free(data->enable_gpio);
> err_alloc:
> if (data->exit)
> data->exit(&pdev->dev);
> @@ -269,6 +307,9 @@ static int pwm_backlight_remove(struct platform_device *pdev)
> backlight_device_unregister(bl);
> pwm_config(pb->pwm, 0, pb->period);
> pwm_disable(pb->pwm);
> + pwm_backlight_disable(pb);
> + if (gpio_is_valid(pb->enable_gpio))
> + gpio_free(pb->enable_gpio);
> if (pb->exit)
> pb->exit(&pdev->dev);
> return 0;
> @@ -284,6 +325,7 @@ static int pwm_backlight_suspend(struct device *dev)
> pb->notify(pb->dev, 0);
> pwm_config(pb->pwm, 0, pb->period);
> pwm_disable(pb->pwm);
> + pwm_backlight_disable(pb);

Another good reason to move pwm_disable inside pwm_backlight_disable. :)

Alex.



\
 
 \ /
  Last update: 2013-03-05 07:02    [W:0.215 / U:0.172 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site