[V4,9/9] pwm_bl: Add mandatory backlight enable regulator
diff mbox

Message ID 1363719573-20926-10-git-send-email-achew@nvidia.com
State New, archived
Headers show

Commit Message

achew@nvidia.com March 19, 2013, 6:59 p.m. UTC
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@nvidia.com>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Tested-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
---
 .../bindings/video/backlight/pwm-backlight.txt     | 14 +++++
 drivers/video/backlight/pwm_bl.c                   | 59 ++++++++++++++++++----
 2 files changed, 63 insertions(+), 10 deletions(-)

Comments

Stephen Warren March 20, 2013, 6 p.m. UTC | #1
On 03/19/2013 12:59 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.

> 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.

"enable" doesn't seem like the right name here; if this really is an
"enable" input, then it's not a regulator. If you're calling it "enable"
because the regulator is usually controlled by a GPIO that enables it,
then what you really have is a regulator that provides power to the
backlight, and the method that you enable that regulator is irrelevant.

Put another way, wouldn't "power" be a better name, thus making the
property "power-supply"? Although that property name migth be considered
to have some negative correlation with other concepts, so if people
object to that, perhaps e.g. "vdd-supply"?
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Thierry Reding March 20, 2013, 10:19 p.m. UTC | #2
On Wed, Mar 20, 2013 at 12:00:10PM -0600, Stephen Warren wrote:
> On 03/19/2013 12:59 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.
> 
> > 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.
> 
> "enable" doesn't seem like the right name here; if this really is an
> "enable" input, then it's not a regulator. If you're calling it "enable"
> because the regulator is usually controlled by a GPIO that enables it,
> then what you really have is a regulator that provides power to the
> backlight, and the method that you enable that regulator is irrelevant.
> 
> Put another way, wouldn't "power" be a better name, thus making the
> property "power-supply"? Although that property name migth be considered
> to have some negative correlation with other concepts, so if people
> object to that, perhaps e.g. "vdd-supply"?

"power" sounds like a reasonable name to me.

Thierry

Patch
diff mbox

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..e4922f5 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 +38,42 @@  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);
+	int ret;
+
+	/* Bail if we are already enabled. */
+	if (pb->enabled)
+		return;
+
+	pwm_enable(pb->pwm);
+
+	ret = regulator_enable(pb->enable_supply);
+	if (ret)
+		dev_warn(&bl->dev, "Failed to enable regulator: %d", ret);
+
+	pb->enabled = true;
+}
+
+static void pwm_backlight_disable(struct backlight_device *bl)
+{
+	struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev);
+	int ret;
+
+	/* Bail if we are already disabled. */
+	if (!pb->enabled)
+		return;
+
+	ret = regulator_disable(pb->enable_supply);
+	if (ret)
+		dev_warn(&bl->dev, "Failed to disable regulator: %d", ret);
+
+	pwm_disable(pb->pwm);
+
+	pb->enabled = false;
+}
+
 static int pwm_backlight_update_status(struct backlight_device *bl)
 {
 	struct pwm_bl_data *pb = bl_get_data(bl);
@@ -51,7 +90,7 @@  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 +104,7 @@  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 +177,6 @@  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 +239,12 @@  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 +307,7 @@  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 +322,7 @@  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;