[v4,1/2] backlight: pwm_bl: Move the checks for initial power state to a separate function

Submitted by Péter Ujfalusi on Nov. 22, 2016, 1:41 p.m.

Details

Message ID 20161122134123.1209-2-peter.ujfalusi@ti.com
State New
Headers show

Commit Message

Péter Ujfalusi Nov. 22, 2016, 1:41 p.m.
Move the checks to select the initial state for the backlight to a new
function and document the checks we are doing.

With the separate function it is going to be easier to fix or improve the
initial power state configuration later and it is easier to read the code.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Reviewed-by: Thierry Reding <treding@nvidia.com>
---
 drivers/video/backlight/pwm_bl.c | 56 ++++++++++++++++++++++++++--------------
 1 file changed, 37 insertions(+), 19 deletions(-)

Comments

Lee Jones Dec. 9, 2016, 9:13 a.m.
On Tue, 22 Nov 2016, Peter Ujfalusi wrote:

> Move the checks to select the initial state for the backlight to a new
> function and document the checks we are doing.
> 
> With the separate function it is going to be easier to fix or improve the
> initial power state configuration later and it is easier to read the code.
> 
> Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
> Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
> Reviewed-by: Thierry Reding <treding@nvidia.com>
> ---
>  drivers/video/backlight/pwm_bl.c | 56 ++++++++++++++++++++++++++--------------
>  1 file changed, 37 insertions(+), 19 deletions(-)

Applied for v4.11, thanks.

> diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
> index 12614006211e..5712ddd053dd 100644
> --- a/drivers/video/backlight/pwm_bl.c
> +++ b/drivers/video/backlight/pwm_bl.c
> @@ -192,6 +192,32 @@ static int pwm_backlight_parse_dt(struct device *dev,
>  }
>  #endif
>  
> +static int pwm_backlight_initial_power_state(const struct pwm_bl_data *pb)
> +{
> +	struct device_node *node = pb->dev->of_node;
> +
> +	/* Not booted with device tree or no phandle link to the node */
> +	if (!node || !node->phandle)
> +		return FB_BLANK_UNBLANK;
> +
> +	/*
> +	 * If the driver is probed from the device tree and there is a
> +	 * phandle link pointing to the backlight node, it is safe to
> +	 * assume that another driver will enable the backlight at the
> +	 * appropriate time. Therefore, if it is disabled, keep it so.
> +	 */
> +
> +	/* if the enable GPIO is disabled, do not enable the backlight */
> +	if (pb->enable_gpio && gpiod_get_value(pb->enable_gpio) == 0)
> +		return FB_BLANK_POWERDOWN;
> +
> +	/* The regulator is disabled, do not enable the backlight */
> +	if (!regulator_is_enabled(pb->power_supply))
> +		return FB_BLANK_POWERDOWN;
> +
> +	return FB_BLANK_UNBLANK;
> +}
> +
>  static int pwm_backlight_probe(struct platform_device *pdev)
>  {
>  	struct platform_pwm_backlight_data *data = dev_get_platdata(&pdev->dev);
> @@ -200,7 +226,6 @@ static int pwm_backlight_probe(struct platform_device *pdev)
>  	struct backlight_device *bl;
>  	struct device_node *node = pdev->dev.of_node;
>  	struct pwm_bl_data *pb;
> -	int initial_blank = FB_BLANK_UNBLANK;
>  	struct pwm_args pargs;
>  	int ret;
>  
> @@ -267,20 +292,16 @@ static int pwm_backlight_probe(struct platform_device *pdev)
>  		pb->enable_gpio = gpio_to_desc(data->enable_gpio);
>  	}
>  
> -	if (pb->enable_gpio) {
> -		/*
> -		 * If the driver is probed from the device tree and there is a
> -		 * phandle link pointing to the backlight node, it is safe to
> -		 * assume that another driver will enable the backlight at the
> -		 * appropriate time. Therefore, if it is disabled, keep it so.
> -		 */
> -		if (node && node->phandle &&
> -		    gpiod_get_direction(pb->enable_gpio) == GPIOF_DIR_OUT &&
> -		    gpiod_get_value(pb->enable_gpio) == 0)
> -			initial_blank = FB_BLANK_POWERDOWN;
> -		else
> -			gpiod_direction_output(pb->enable_gpio, 1);
> -	}
> +	/*
> +	 * If the GPIO is configured as input, change the direction to output
> +	 * and set the GPIO as active.
> +	 * Do not force the GPIO to active when it was already output as it
> +	 * could cause backlight flickering or we would enable the backlight too
> +	 * early. Leave the decision of the initial backlight state for later.
> +	 */
> +	if (pb->enable_gpio &&
> +	    gpiod_get_direction(pb->enable_gpio) == GPIOF_DIR_IN)
> +		gpiod_direction_output(pb->enable_gpio, 1);
>  
>  	pb->power_supply = devm_regulator_get(&pdev->dev, "power");
>  	if (IS_ERR(pb->power_supply)) {
> @@ -288,9 +309,6 @@ static int pwm_backlight_probe(struct platform_device *pdev)
>  		goto err_alloc;
>  	}
>  
> -	if (node && node->phandle && !regulator_is_enabled(pb->power_supply))
> -		initial_blank = FB_BLANK_POWERDOWN;
> -
>  	pb->pwm = devm_pwm_get(&pdev->dev, NULL);
>  	if (IS_ERR(pb->pwm) && PTR_ERR(pb->pwm) != -EPROBE_DEFER && !node) {
>  		dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n");
> @@ -347,7 +365,7 @@ static int pwm_backlight_probe(struct platform_device *pdev)
>  	}
>  
>  	bl->props.brightness = data->dft_brightness;
> -	bl->props.power = initial_blank;
> +	bl->props.power = pwm_backlight_initial_power_state(pb);
>  	backlight_update_status(bl);
>  
>  	platform_set_drvdata(pdev, bl);
Geert Uytterhoeven March 21, 2017, 6:48 p.m.
Hi Peter,

On Tue, Nov 22, 2016 at 2:41 PM, Peter Ujfalusi <peter.ujfalusi@ti.com> wrote:
> Move the checks to select the initial state for the backlight to a new
> function and document the checks we are doing.

This is far from a simple "move"...

> With the separate function it is going to be easier to fix or improve the
> initial power state configuration later and it is easier to read the code.
>
> Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
> Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
> Reviewed-by: Thierry Reding <treding@nvidia.com>

This patch (commit 7613c922315e308a in v4.11-rc1) broke the display on
r8a7740/armadillo.

> @@ -267,20 +292,16 @@ static int pwm_backlight_probe(struct platform_device *pdev)
>                 pb->enable_gpio = gpio_to_desc(data->enable_gpio);
>         }
>
> -       if (pb->enable_gpio) {
> -               /*
> -                * If the driver is probed from the device tree and there is a
> -                * phandle link pointing to the backlight node, it is safe to
> -                * assume that another driver will enable the backlight at the
> -                * appropriate time. Therefore, if it is disabled, keep it so.
> -                */
> -               if (node && node->phandle &&
> -                   gpiod_get_direction(pb->enable_gpio) == GPIOF_DIR_OUT &&
> -                   gpiod_get_value(pb->enable_gpio) == 0)
> -                       initial_blank = FB_BLANK_POWERDOWN;
> -               else
> -                       gpiod_direction_output(pb->enable_gpio, 1);

In my case, "node" points to the "/backlight" node, but phandle is NULL.
Hence before, gpiod_direction_output() was called to enable the GPIO...

> -       }
> +       /*
> +        * If the GPIO is configured as input, change the direction to output
> +        * and set the GPIO as active.
> +        * Do not force the GPIO to active when it was already output as it
> +        * could cause backlight flickering or we would enable the backlight too
> +        * early. Leave the decision of the initial backlight state for later.
> +        */
> +       if (pb->enable_gpio &&
> +           gpiod_get_direction(pb->enable_gpio) == GPIOF_DIR_IN)
> +               gpiod_direction_output(pb->enable_gpio, 1);

... while now it's no longer called, as gpiod_get_direction() returns
-EINVAL.

Indeed, r8a7740_pfc does not implement the .get_direction() callback,
so gpiod_get_direction() always returns -EINVAL, which is never equal
to GPIOF_DIR_IN.

Restoring the old behavior by changing the above test to

        if (pb->enable_gpio &&
            (!node || !node->phandle ||
             gpiod_get_direction(pb->enable_gpio) == GPIOF_DIR_IN))

fixes the display for me, but leads to a more complex expression.

However, changing the test to

        if (pb->enable_gpio &&
            gpiod_get_direction(pb->enable_gpio) != GPIOF_DIR_OUT)

also fixes the display, as an error is always different from GPIOF_DIR_OUT.

Anyone with comments or suggestions to fix this for real?

Thanks!

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
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To unsubscribe from this list: send the line "unsubscribe linux-pwm" in
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Philipp Zabel March 22, 2017, 10:46 a.m.
On Tue, 2017-03-21 at 19:48 +0100, Geert Uytterhoeven wrote:
> Hi Peter,
> 
> On Tue, Nov 22, 2016 at 2:41 PM, Peter Ujfalusi <peter.ujfalusi@ti.com> wrote:
> > Move the checks to select the initial state for the backlight to a new
> > function and document the checks we are doing.
> 
> This is far from a simple "move"...
> 
> > With the separate function it is going to be easier to fix or improve the
> > initial power state configuration later and it is easier to read the code.
> >
> > Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
> > Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
> > Reviewed-by: Thierry Reding <treding@nvidia.com>
> 
> This patch (commit 7613c922315e308a in v4.11-rc1) broke the display on
> r8a7740/armadillo.
> 
> > @@ -267,20 +292,16 @@ static int pwm_backlight_probe(struct platform_device *pdev)
> >                 pb->enable_gpio = gpio_to_desc(data->enable_gpio);
> >         }
> >
> > -       if (pb->enable_gpio) {
> > -               /*
> > -                * If the driver is probed from the device tree and there is a
> > -                * phandle link pointing to the backlight node, it is safe to
> > -                * assume that another driver will enable the backlight at the
> > -                * appropriate time. Therefore, if it is disabled, keep it so.
> > -                */
> > -               if (node && node->phandle &&
> > -                   gpiod_get_direction(pb->enable_gpio) == GPIOF_DIR_OUT &&
> > -                   gpiod_get_value(pb->enable_gpio) == 0)
> > -                       initial_blank = FB_BLANK_POWERDOWN;
> > -               else
> > -                       gpiod_direction_output(pb->enable_gpio, 1);
> 
> In my case, "node" points to the "/backlight" node, but phandle is NULL.
> Hence before, gpiod_direction_output() was called to enable the GPIO...
> 
> > -       }
> > +       /*
> > +        * If the GPIO is configured as input, change the direction to output
> > +        * and set the GPIO as active.
> > +        * Do not force the GPIO to active when it was already output as it
> > +        * could cause backlight flickering or we would enable the backlight too
> > +        * early. Leave the decision of the initial backlight state for later.
> > +        */
> > +       if (pb->enable_gpio &&
> > +           gpiod_get_direction(pb->enable_gpio) == GPIOF_DIR_IN)
> > +               gpiod_direction_output(pb->enable_gpio, 1);
> 
> ... while now it's no longer called, as gpiod_get_direction() returns
> -EINVAL.
> 
> Indeed, r8a7740_pfc does not implement the .get_direction() callback,
> so gpiod_get_direction() always returns -EINVAL, which is never equal
> to GPIOF_DIR_IN.

Oh, I didn't think about this at all, anymore. Though I believe to
remember that this was the reason that I checked for
(gpiod_get_direction(pb->enable_gpio) == GPIOF_DIR_OUT) before, so ...

> Restoring the old behavior by changing the above test to
> 
>         if (pb->enable_gpio &&
>             (!node || !node->phandle ||
>              gpiod_get_direction(pb->enable_gpio) == GPIOF_DIR_IN))
> 
> fixes the display for me, but leads to a more complex expression.
> 
> However, changing the test to
> 
>         if (pb->enable_gpio &&
>             gpiod_get_direction(pb->enable_gpio) != GPIOF_DIR_OUT)
> 
> also fixes the display, as an error is always different from GPIOF_DIR_OUT.
>
> Anyone with comments or suggestions to fix this for real?

... I'm in favor of the latter, as this is closer to the initial
intention. I'd also mention this in the comment:

       /*
        * If the GPIO is not known to be already configured as output, that is,
        * if gpiod_get_direction returns either GPIOF_DIR_IN or -EINVAL, change
        * the direction to output and set the GPIO as active.
        * Do not force the GPIO to active when it was already output as it
        * could cause backlight flickering or we would enable the backlight too
        * early. Leave the decision of the initial backlight state for later.
        */

regards
Philipp

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Geert Uytterhoeven March 22, 2017, 12:30 p.m.
Hi Philip,

On Wed, Mar 22, 2017 at 11:46 AM, Philipp Zabel <p.zabel@pengutronix.de> wrote:
> On Tue, 2017-03-21 at 19:48 +0100, Geert Uytterhoeven wrote:
>> On Tue, Nov 22, 2016 at 2:41 PM, Peter Ujfalusi <peter.ujfalusi@ti.com> wrote:
>> > Move the checks to select the initial state for the backlight to a new
>> > function and document the checks we are doing.
>>
>> This is far from a simple "move"...
>>
>> > With the separate function it is going to be easier to fix or improve the
>> > initial power state configuration later and it is easier to read the code.
>> >
>> > Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
>> > Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
>> > Reviewed-by: Thierry Reding <treding@nvidia.com>
>>
>> This patch (commit 7613c922315e308a in v4.11-rc1) broke the display on
>> r8a7740/armadillo.
>>
>> > @@ -267,20 +292,16 @@ static int pwm_backlight_probe(struct platform_device *pdev)
>> >                 pb->enable_gpio = gpio_to_desc(data->enable_gpio);
>> >         }
>> >
>> > -       if (pb->enable_gpio) {
>> > -               /*
>> > -                * If the driver is probed from the device tree and there is a
>> > -                * phandle link pointing to the backlight node, it is safe to
>> > -                * assume that another driver will enable the backlight at the
>> > -                * appropriate time. Therefore, if it is disabled, keep it so.
>> > -                */
>> > -               if (node && node->phandle &&
>> > -                   gpiod_get_direction(pb->enable_gpio) == GPIOF_DIR_OUT &&
>> > -                   gpiod_get_value(pb->enable_gpio) == 0)
>> > -                       initial_blank = FB_BLANK_POWERDOWN;
>> > -               else
>> > -                       gpiod_direction_output(pb->enable_gpio, 1);
>>
>> In my case, "node" points to the "/backlight" node, but phandle is NULL.
>> Hence before, gpiod_direction_output() was called to enable the GPIO...
>>
>> > -       }
>> > +       /*
>> > +        * If the GPIO is configured as input, change the direction to output
>> > +        * and set the GPIO as active.
>> > +        * Do not force the GPIO to active when it was already output as it
>> > +        * could cause backlight flickering or we would enable the backlight too
>> > +        * early. Leave the decision of the initial backlight state for later.
>> > +        */
>> > +       if (pb->enable_gpio &&
>> > +           gpiod_get_direction(pb->enable_gpio) == GPIOF_DIR_IN)
>> > +               gpiod_direction_output(pb->enable_gpio, 1);
>>
>> ... while now it's no longer called, as gpiod_get_direction() returns
>> -EINVAL.
>>
>> Indeed, r8a7740_pfc does not implement the .get_direction() callback,
>> so gpiod_get_direction() always returns -EINVAL, which is never equal
>> to GPIOF_DIR_IN.
>
> Oh, I didn't think about this at all, anymore. Though I believe to
> remember that this was the reason that I checked for
> (gpiod_get_direction(pb->enable_gpio) == GPIOF_DIR_OUT) before, so ...
>
>> Restoring the old behavior by changing the above test to
>>
>>         if (pb->enable_gpio &&
>>             (!node || !node->phandle ||
>>              gpiod_get_direction(pb->enable_gpio) == GPIOF_DIR_IN))
>>
>> fixes the display for me, but leads to a more complex expression.
>>
>> However, changing the test to
>>
>>         if (pb->enable_gpio &&
>>             gpiod_get_direction(pb->enable_gpio) != GPIOF_DIR_OUT)
>>
>> also fixes the display, as an error is always different from GPIOF_DIR_OUT.
>>
>> Anyone with comments or suggestions to fix this for real?
>
> ... I'm in favor of the latter, as this is closer to the initial
> intention. I'd also mention this in the comment:
>
>        /*
>         * If the GPIO is not known to be already configured as output, that is,
>         * if gpiod_get_direction returns either GPIOF_DIR_IN or -EINVAL, change
>         * the direction to output and set the GPIO as active.
>         * Do not force the GPIO to active when it was already output as it
>         * could cause backlight flickering or we would enable the backlight too
>         * early. Leave the decision of the initial backlight state for later.
>         */

Thanks, I'll cook up a patch.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
--
To unsubscribe from this list: send the line "unsubscribe linux-pwm" in
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Patch hide | download patch | download mbox

diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
index 12614006211e..5712ddd053dd 100644
--- a/drivers/video/backlight/pwm_bl.c
+++ b/drivers/video/backlight/pwm_bl.c
@@ -192,6 +192,32 @@  static int pwm_backlight_parse_dt(struct device *dev,
 }
 #endif
 
+static int pwm_backlight_initial_power_state(const struct pwm_bl_data *pb)
+{
+	struct device_node *node = pb->dev->of_node;
+
+	/* Not booted with device tree or no phandle link to the node */
+	if (!node || !node->phandle)
+		return FB_BLANK_UNBLANK;
+
+	/*
+	 * If the driver is probed from the device tree and there is a
+	 * phandle link pointing to the backlight node, it is safe to
+	 * assume that another driver will enable the backlight at the
+	 * appropriate time. Therefore, if it is disabled, keep it so.
+	 */
+
+	/* if the enable GPIO is disabled, do not enable the backlight */
+	if (pb->enable_gpio && gpiod_get_value(pb->enable_gpio) == 0)
+		return FB_BLANK_POWERDOWN;
+
+	/* The regulator is disabled, do not enable the backlight */
+	if (!regulator_is_enabled(pb->power_supply))
+		return FB_BLANK_POWERDOWN;
+
+	return FB_BLANK_UNBLANK;
+}
+
 static int pwm_backlight_probe(struct platform_device *pdev)
 {
 	struct platform_pwm_backlight_data *data = dev_get_platdata(&pdev->dev);
@@ -200,7 +226,6 @@  static int pwm_backlight_probe(struct platform_device *pdev)
 	struct backlight_device *bl;
 	struct device_node *node = pdev->dev.of_node;
 	struct pwm_bl_data *pb;
-	int initial_blank = FB_BLANK_UNBLANK;
 	struct pwm_args pargs;
 	int ret;
 
@@ -267,20 +292,16 @@  static int pwm_backlight_probe(struct platform_device *pdev)
 		pb->enable_gpio = gpio_to_desc(data->enable_gpio);
 	}
 
-	if (pb->enable_gpio) {
-		/*
-		 * If the driver is probed from the device tree and there is a
-		 * phandle link pointing to the backlight node, it is safe to
-		 * assume that another driver will enable the backlight at the
-		 * appropriate time. Therefore, if it is disabled, keep it so.
-		 */
-		if (node && node->phandle &&
-		    gpiod_get_direction(pb->enable_gpio) == GPIOF_DIR_OUT &&
-		    gpiod_get_value(pb->enable_gpio) == 0)
-			initial_blank = FB_BLANK_POWERDOWN;
-		else
-			gpiod_direction_output(pb->enable_gpio, 1);
-	}
+	/*
+	 * If the GPIO is configured as input, change the direction to output
+	 * and set the GPIO as active.
+	 * Do not force the GPIO to active when it was already output as it
+	 * could cause backlight flickering or we would enable the backlight too
+	 * early. Leave the decision of the initial backlight state for later.
+	 */
+	if (pb->enable_gpio &&
+	    gpiod_get_direction(pb->enable_gpio) == GPIOF_DIR_IN)
+		gpiod_direction_output(pb->enable_gpio, 1);
 
 	pb->power_supply = devm_regulator_get(&pdev->dev, "power");
 	if (IS_ERR(pb->power_supply)) {
@@ -288,9 +309,6 @@  static int pwm_backlight_probe(struct platform_device *pdev)
 		goto err_alloc;
 	}
 
-	if (node && node->phandle && !regulator_is_enabled(pb->power_supply))
-		initial_blank = FB_BLANK_POWERDOWN;
-
 	pb->pwm = devm_pwm_get(&pdev->dev, NULL);
 	if (IS_ERR(pb->pwm) && PTR_ERR(pb->pwm) != -EPROBE_DEFER && !node) {
 		dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n");
@@ -347,7 +365,7 @@  static int pwm_backlight_probe(struct platform_device *pdev)
 	}
 
 	bl->props.brightness = data->dft_brightness;
-	bl->props.power = initial_blank;
+	bl->props.power = pwm_backlight_initial_power_state(pb);
 	backlight_update_status(bl);
 
 	platform_set_drvdata(pdev, bl);