On 03/12/2013 11:22 PM, Andrew Chew wrote:
> Many backlights need to be explicitly enabled. Typically, this is done
> with a GPIO. For flexibility, we generalize the enable mechanism to a
> regulator.
>
> If an enable regulator is not needed, then a dummy regulator can be given
> to the backlight driver. If a GPIO is used to enable the backlight,
> then a fixed regulator can be instantiated to control the GPIO.
>
> The backlight enable regulator can be specified in the device tree node
> for the backlight, or can be done with legacy board setup code in the
> usual way.
>
> Signed-off-by: Andrew Chew <achew@xxxxxxxxxx>
> Reviewed-by: Alexandre Courbot <acourbot@xxxxxxxxxx>
> ---
> .../bindings/video/backlight/pwm-backlight.txt | 14 +++++
> drivers/video/backlight/pwm_bl.c | 55 ++++++++++++++++----
> 2 files changed, 59 insertions(+), 10 deletions(-)
>
> diff --git a/Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt b/Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt
> index 1e4fc72..7e2e089 100644
> --- a/Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt
> +++ b/Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt
> @@ -10,6 +10,11 @@ Required properties:
> last value in the array represents a 100% duty cycle (brightest).
> - default-brightness-level: the default brightness level (index into the
> array defined by the "brightness-levels" property)
> + - enable-supply: A phandle to the regulator device tree node. This
> + regulator will be turned on and off as the pwm is enabled and disabled.
> + Many backlights are enabled via a GPIO. In this case, we instantiate
> + a fixed regulator and give that to enable-supply. If a regulator
> + is not needed, then provide a dummy fixed regulator.
>
> Optional properties:
> - pwm-names: a list of names for the PWM devices specified in the
> @@ -19,10 +24,19 @@ Optional properties:
>
> Example:
>
> + bl_en: fixed-regulator {
> + compatible = "regulator-fixed";
> + regulator-name = "bl-en-supply";
> + regulator-boot-on;
> + gpio = <&some_gpio>;
> + enable-active-high;
> + };
> +
> backlight {
> compatible = "pwm-backlight";
> pwms = <&pwm 0 5000000>;
>
> brightness-levels = <0 4 8 16 32 64 128 255>;
> default-brightness-level = <6>;
> + enable-supply = <&bl_en>;
> };
> diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
> index 1fea627..c557c51 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/regulator/consumer.h>
>
> struct pwm_bl_data {
> struct pwm_device *pwm;
> struct device *dev;
> + bool enabled;
> + struct regulator *enable_supply;
> unsigned int period;
> unsigned int lth_brightness;
> unsigned int *levels;
> @@ -35,6 +38,38 @@ struct pwm_bl_data {
> void (*exit)(struct device *);
> };
>
> +static void pwm_backlight_enable(struct backlight_device *bl)
> +{
> + struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev);
> +
> + /* Bail if we are already enabled. */
> + if (pb->enabled)
> + return;
> +
> + pwm_enable(pb->pwm);
> +
> + if (regulator_enable(pb->enable_supply) != 0)
I would loose the '!= 0'
> + dev_warn(&bl->dev, "Failed to enable regulator");
> +
> + pb->enabled = true;
> +}
> +
> +static void pwm_backlight_disable(struct backlight_device *bl)
> +{
> + struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev);
> +
> + /* Bail if we are already disabled. */
> + if (!pb->enabled)
> + return;
> +
> + if (regulator_disable(pb->enable_supply) != 0)
> + dev_warn(&bl->dev, "Failed to disable regulator");
> +
> + pwm_disable(pb->pwm);
> +
> + pb->enabled = false;
> +}
Would it not be better to have some locking here since the code started to use
flag for state tracking?
> +
> static int pwm_backlight_update_status(struct backlight_device *bl)
> {
> struct pwm_bl_data *pb = bl_get_data(bl);
> @@ -51,7 +86,7 @@ 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(bl);
> } else {
> int duty_cycle;
>
> @@ -65,7 +100,7 @@ static int pwm_backlight_update_status(struct backlight_device *bl)
> duty_cycle = pb->lth_brightness +
> (duty_cycle * (pb->period - pb->lth_brightness) / max);
> pwm_config(pb->pwm, duty_cycle, pb->period);
> - pwm_enable(pb->pwm);
> + pwm_backlight_enable(bl);
> }
>
> if (pb->notify_after)
> @@ -138,12 +173,6 @@ static int pwm_backlight_parse_dt(struct device *dev,
> data->max_brightness--;
> }
>
> - /*
> - * TODO: Most users of this driver use a number of GPIOs to control
> - * backlight power. Support for specifying these needs to be
> - * added.
> - */
> -
> return 0;
> }
>
> @@ -206,6 +235,12 @@ static int pwm_backlight_probe(struct platform_device *pdev)
> pb->exit = data->exit;
> pb->dev = &pdev->dev;
>
> + pb->enable_supply = devm_regulator_get(&pdev->dev, "enable");
> + if (IS_ERR(pb->enable_supply)) {
> + ret = PTR_ERR(pb->enable_supply);
> + 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");
> @@ -268,7 +303,7 @@ 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(bl);
> if (pb->exit)
> pb->exit(&pdev->dev);
> return 0;
> @@ -283,7 +318,7 @@ static int pwm_backlight_suspend(struct device *dev)
> if (pb->notify)
> pb->notify(pb->dev, 0);
> pwm_config(pb->pwm, 0, pb->period);
> - pwm_disable(pb->pwm);
> + pwm_backlight_disable(bl);
> if (pb->notify_after)
> pb->notify_after(pb->dev, 0);
> return 0;
>
--
Péter
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