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    Subject[PATCH] pwm-backlight: add regulator and GPIO support
    Date
    Add support for an optional power regulator and enable/disable GPIO.
    This scheme is commonly used in embedded systems.

    Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
    ---
    .../bindings/video/backlight/pwm-backlight | 4 +
    drivers/video/backlight/pwm_bl.c | 86 ++++++++++++++++++----
    include/linux/pwm_backlight.h | 5 ++
    3 files changed, 79 insertions(+), 16 deletions(-)

    diff --git a/Documentation/devicetree/bindings/video/backlight/pwm-backlight b/Documentation/devicetree/bindings/video/backlight/pwm-backlight
    index 1e4fc72..85cbb7b 100644
    --- a/Documentation/devicetree/bindings/video/backlight/pwm-backlight
    +++ b/Documentation/devicetree/bindings/video/backlight/pwm-backlight
    @@ -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])
    + - power-supply: a reference to a regulator used to control the backlight power
    + - enable-gpios: a reference to a GPIO used to enable/disable the backlight

    [0]: Documentation/devicetree/bindings/pwm/pwm.txt

    @@ -25,4 +27,6 @@ Example:

    brightness-levels = <0 4 8 16 32 64 128 255>;
    default-brightness-level = <6>;
    + power-supply = <&backlight_reg>;
    + enable-gpios = <&gpio 6 0>;
    };
    diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
    index 057389d..821e03e 100644
    --- a/drivers/video/backlight/pwm_bl.c
    +++ b/drivers/video/backlight/pwm_bl.c
    @@ -20,6 +20,8 @@
    #include <linux/pwm.h>
    #include <linux/pwm_backlight.h>
    #include <linux/slab.h>
    +#include <linux/of_gpio.h>
    +#include <linux/regulator/consumer.h>

    struct pwm_bl_data {
    struct pwm_device *pwm;
    @@ -27,6 +29,9 @@ struct pwm_bl_data {
    unsigned int period;
    unsigned int lth_brightness;
    unsigned int *levels;
    + bool enabled;
    + struct regulator *power_reg;
    + int enable_gpio;
    int (*notify)(struct device *,
    int brightness);
    void (*notify_after)(struct device *,
    @@ -35,6 +40,40 @@ struct pwm_bl_data {
    void (*exit)(struct device *);
    };

    +static void pwm_backlight_off(struct pwm_bl_data *pb)
    +{
    + if (!pb->enabled)
    + return;
    +
    + if (gpio_is_valid(pb->enable_gpio))
    + gpio_set_value_cansleep(pb->enable_gpio, 0);
    +
    + if (pb->power_reg)
    + regulator_disable(pb->power_reg);
    +
    + pwm_config(pb->pwm, 0, pb->period);
    + pwm_disable(pb->pwm);
    +
    + pb->enabled = false;
    +}
    +
    +static void pwm_backlight_on(struct pwm_bl_data *pb, int brightness)
    +{
    + pwm_config(pb->pwm, brightness, pb->period);
    + pwm_enable(pb->pwm);
    +
    + if (pb->enabled)
    + return;
    +
    + if (pb->power_reg)
    + regulator_enable(pb->power_reg);
    +
    + if (gpio_is_valid(pb->enable_gpio))
    + gpio_set_value_cansleep(pb->enable_gpio, 1);
    +
    + pb->enabled = true;
    +}
    +
    static int pwm_backlight_update_status(struct backlight_device *bl)
    {
    struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev);
    @@ -51,8 +90,7 @@ static int pwm_backlight_update_status(struct backlight_device *bl)
    brightness = pb->notify(pb->dev, brightness);

    if (brightness == 0) {
    - pwm_config(pb->pwm, 0, pb->period);
    - pwm_disable(pb->pwm);
    + pwm_backlight_off(pb);
    } else {
    if (pb->levels) {
    brightness = pb->levels[brightness];
    @@ -61,8 +99,7 @@ static int pwm_backlight_update_status(struct backlight_device *bl)

    brightness = pb->lth_brightness +
    (brightness * (pb->period - pb->lth_brightness) / max);
    - pwm_config(pb->pwm, brightness, pb->period);
    - pwm_enable(pb->pwm);
    + pwm_backlight_on(pb, brightness);
    }

    if (pb->notify_after)
    @@ -141,11 +178,14 @@ 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.
    - */
    + ret = of_get_named_gpio(node, "enable-gpios", 0);
    + if (ret >= 0) {
    + data->enable_gpio = of_get_named_gpio(node, "enable-gpios", 0);
    + data->use_enable_gpio = true;
    + } else if (ret != -ENOENT) {
    + /* GPIO is optional, so ENOENT is not an error here */
    + return ret;
    + }

    return 0;
    }
    @@ -176,7 +216,9 @@ static int pwm_backlight_probe(struct platform_device *pdev)

    if (!data) {
    ret = pwm_backlight_parse_dt(&pdev->dev, &defdata);
    - if (ret < 0) {
    + if (ret == -EPROBE_DEFER) {
    + return ret;
    + } else if (ret < 0) {
    dev_err(&pdev->dev, "failed to find platform data\n");
    return ret;
    }
    @@ -221,8 +263,6 @@ static int pwm_backlight_probe(struct platform_device *pdev)
    }
    }

    - dev_dbg(&pdev->dev, "got pwm for backlight\n");
    -
    /*
    * The DT case will set the pwm_period_ns field to 0 and store the
    * period, parsed from the DT, in the PWM device. For the non-DT case,
    @@ -231,6 +271,22 @@ static int pwm_backlight_probe(struct platform_device *pdev)
    if (data->pwm_period_ns > 0)
    pwm_set_period(pb->pwm, data->pwm_period_ns);

    +
    + pb->power_reg = devm_regulator_get(&pdev->dev, "power");
    + if (IS_ERR(pb->power_reg))
    + return PTR_ERR(pb->power_reg);
    +
    + pb->enable_gpio = -EINVAL;
    + if (data->use_enable_gpio) {
    + ret = devm_gpio_request_one(&pdev->dev, data->enable_gpio,
    + GPIOF_OUT_INIT_HIGH, "backlight_enable");
    + if (ret)
    + dev_warn(&pdev->dev,
    + "error %d requesting control gpio\n", ret);
    + else
    + pb->enable_gpio = data->enable_gpio;
    + }
    +
    pb->period = pwm_get_period(pb->pwm);
    pb->lth_brightness = data->lth_brightness * (pb->period / max);

    @@ -265,8 +321,7 @@ static int pwm_backlight_remove(struct platform_device *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_backlight_off(pb);
    pwm_put(pb->pwm);
    if (pb->exit)
    pb->exit(&pdev->dev);
    @@ -281,8 +336,7 @@ 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_off(pb);
    if (pb->notify_after)
    pb->notify_after(pb->dev, 0);
    return 0;
    diff --git a/include/linux/pwm_backlight.h b/include/linux/pwm_backlight.h
    index 56f4a86..5ae2cd0 100644
    --- a/include/linux/pwm_backlight.h
    +++ b/include/linux/pwm_backlight.h
    @@ -18,6 +18,11 @@ struct platform_pwm_backlight_data {
    void (*notify_after)(struct device *dev, int brightness);
    void (*exit)(struct device *dev);
    int (*check_fb)(struct device *dev, struct fb_info *info);
    + /* optional GPIO that enables/disables the backlight */
    + int enable_gpio;
    + /* 0 (default initialization value) is a valid GPIO number. Make use of
    + * control gpio explicit to avoid bad surprises. */
    + bool use_enable_gpio;
    };

    #endif
    --
    1.7.11.1


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