[PATCH] pwm-backlight: add regulator and GPIO support

Alexandre Courbot
2012-06-29T13:21:07Z

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