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Subject[PATCH 1/1] pwm_bl: Add support for backlight enable GPIO
Date
The backlight enable GPIO is specified in the device tree node for
backlight.

Signed-off-by: Andrew Chew <achew@nvidia.com>
---
.../bindings/video/backlight/pwm-backlight.txt | 2 ++
drivers/video/backlight/pwm_bl.c | 32 +++++++++++++++++---
include/linux/pwm_backlight.h | 2 ++
3 files changed, 32 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..f29f9c7 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;
@@ -146,10 +149,15 @@ 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 +215,23 @@ 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");
+ 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 +240,7 @@ 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 +274,9 @@ 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 +291,8 @@ static int pwm_backlight_remove(struct platform_device *pdev)
backlight_device_unregister(bl);
pwm_config(pb->pwm, 0, pb->period);
pwm_disable(pb->pwm);
+ if (gpio_is_valid(pb->enable_gpio))
+ gpio_free(pb->enable_gpio);
if (pb->exit)
pb->exit(&pdev->dev);
return 0;
diff --git a/include/linux/pwm_backlight.h b/include/linux/pwm_backlight.h
index 56f4a86..2706805 100644
--- a/include/linux/pwm_backlight.h
+++ b/include/linux/pwm_backlight.h
@@ -8,6 +8,8 @@

struct platform_pwm_backlight_data {
int pwm_id;
+ int enable_gpio;
+ unsigned int enable_gpio_flags;
unsigned int max_brightness;
unsigned int dft_brightness;
unsigned int lth_brightness;
--
1.7.9.5


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