2017-03-22 17:21:55

by Geert Uytterhoeven

Subject: [PATCH] backlight: pwm_bl: Fix GPIO out for unimplemented .get_direction()

Commit 7613c922315e308a ("backlight: pwm_bl: Move the checks for initial
power state to a separate function") not just moved some code, but made
slight changes in semantics.

If a gpiochip doesn't implement the optional .get_direction() callback,
gpiod_get_direction always returns -EINVAL, which is never equal to
GPIOF_DIR_IN, leading to the GPIO not being configured for output.

To avoid this, invert the test and check for not GPIOF_DIR_OUT instead,
like the original code did.

This restores the display on r8a7740/armadillo.

Fixes: 7613c922315e308a ("backlight: pwm_bl: Move the checks for initial power state to a separate function")
Signed-off-by: Geert Uytterhoeven <[email protected]>
---
drivers/video/backlight/pwm_bl.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
index d7efcb632f7d9dde..002f1ce22bd02032 100644
--- a/drivers/video/backlight/pwm_bl.c
+++ b/drivers/video/backlight/pwm_bl.c
@@ -297,14 +297,15 @@ static int pwm_backlight_probe(struct platform_device *pdev)
}

/*
- * If the GPIO is configured as input, change the direction to output
- * and set the GPIO as active.
+ * 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.
*/
if (pb->enable_gpio &&
- gpiod_get_direction(pb->enable_gpio) == GPIOF_DIR_IN)
+ gpiod_get_direction(pb->enable_gpio) != GPIOF_DIR_OUT)
gpiod_direction_output(pb->enable_gpio, 1);

pb->power_supply = devm_regulator_get(&pdev->dev, "power");
--
2.7.4

2017-03-23 21:13:56

by Peter Ujfalusi

Subject: Re: [PATCH] backlight: pwm_bl: Fix GPIO out for unimplemented .get_direction()

On 03/22/2017 07:21 PM, Geert Uytterhoeven wrote:
> Commit 7613c922315e308a ("backlight: pwm_bl: Move the checks for initial
> power state to a separate function") not just moved some code, but made
> slight changes in semantics.
>
> If a gpiochip doesn't implement the optional .get_direction() callback,
> gpiod_get_direction always returns -EINVAL, which is never equal to
> GPIOF_DIR_IN, leading to the GPIO not being configured for output.

The platforms I have tested the gpio drivers do implement the get_direction()
callback and I was not aware of this behaviour.

> To avoid this, invert the test and check for not GPIOF_DIR_OUT instead,
> like the original code did.
>
> This restores the display on r8a7740/armadillo.
>
> Fixes: 7613c922315e308a ("backlight: pwm_bl: Move the checks for initial power state to a separate function")
> Signed-off-by: Geert Uytterhoeven <[email protected]>

Reviewed-by: Peter Ujfalusi <[email protected]>

> ---
> drivers/video/backlight/pwm_bl.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
> index d7efcb632f7d9dde..002f1ce22bd02032 100644
> --- a/drivers/video/backlight/pwm_bl.c
> +++ b/drivers/video/backlight/pwm_bl.c
> @@ -297,14 +297,15 @@ static int pwm_backlight_probe(struct platform_device *pdev)
> }
>
> /*
> - * If the GPIO is configured as input, change the direction to output
> - * and set the GPIO as active.
> + * 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.
> */
> if (pb->enable_gpio &&
> - gpiod_get_direction(pb->enable_gpio) == GPIOF_DIR_IN)
> + gpiod_get_direction(pb->enable_gpio) != GPIOF_DIR_OUT)
> gpiod_direction_output(pb->enable_gpio, 1);
>
> pb->power_supply = devm_regulator_get(&pdev->dev, "power");
>


--
P?ter

2017-03-24 09:13:47

by Philipp Zabel

Subject: Re: [PATCH] backlight: pwm_bl: Fix GPIO out for unimplemented .get_direction()

On Wed, 2017-03-22 at 18:21 +0100, Geert Uytterhoeven wrote:
> Commit 7613c922315e308a ("backlight: pwm_bl: Move the checks for initial
> power state to a separate function") not just moved some code, but made
> slight changes in semantics.
>
> If a gpiochip doesn't implement the optional .get_direction() callback,
> gpiod_get_direction always returns -EINVAL, which is never equal to
> GPIOF_DIR_IN, leading to the GPIO not being configured for output.
>
> To avoid this, invert the test and check for not GPIOF_DIR_OUT instead,
> like the original code did.
>
> This restores the display on r8a7740/armadillo.
>
> Fixes: 7613c922315e308a ("backlight: pwm_bl: Move the checks for initial power state to a separate function")
> Signed-off-by: Geert Uytterhoeven <[email protected]>

Acked-by: Philipp Zabel <[email protected]>

regards
Philipp

> ---
> drivers/video/backlight/pwm_bl.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
> index d7efcb632f7d9dde..002f1ce22bd02032 100644
> --- a/drivers/video/backlight/pwm_bl.c
> +++ b/drivers/video/backlight/pwm_bl.c
> @@ -297,14 +297,15 @@ static int pwm_backlight_probe(struct platform_device *pdev)
> }
>
> /*
> - * If the GPIO is configured as input, change the direction to output
> - * and set the GPIO as active.
> + * 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.
> */
> if (pb->enable_gpio &&
> - gpiod_get_direction(pb->enable_gpio) == GPIOF_DIR_IN)
> + gpiod_get_direction(pb->enable_gpio) != GPIOF_DIR_OUT)
> gpiod_direction_output(pb->enable_gpio, 1);
>
> pb->power_supply = devm_regulator_get(&pdev->dev, "power");

2017-03-24 16:43:07

by Daniel Thompson

Subject: Re: [PATCH] backlight: pwm_bl: Fix GPIO out for unimplemented .get_direction()

On 22/03/17 17:21, Geert Uytterhoeven wrote:
> Commit 7613c922315e308a ("backlight: pwm_bl: Move the checks for initial
> power state to a separate function") not just moved some code, but made
> slight changes in semantics.
>
> If a gpiochip doesn't implement the optional .get_direction() callback,
> gpiod_get_direction always returns -EINVAL, which is never equal to
> GPIOF_DIR_IN, leading to the GPIO not being configured for output.
>
> To avoid this, invert the test and check for not GPIOF_DIR_OUT instead,
> like the original code did.
>
> This restores the display on r8a7740/armadillo.
>
> Fixes: 7613c922315e308a ("backlight: pwm_bl: Move the checks for initial power state to a separate function")
> Signed-off-by: Geert Uytterhoeven <[email protected]>

Acked-by: Daniel Thommpson <[email protected]>


> ---
> drivers/video/backlight/pwm_bl.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
> index d7efcb632f7d9dde..002f1ce22bd02032 100644
> --- a/drivers/video/backlight/pwm_bl.c
> +++ b/drivers/video/backlight/pwm_bl.c
> @@ -297,14 +297,15 @@ static int pwm_backlight_probe(struct platform_device *pdev)
> }
>
> /*
> - * If the GPIO is configured as input, change the direction to output
> - * and set the GPIO as active.
> + * 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.
> */
> if (pb->enable_gpio &&
> - gpiod_get_direction(pb->enable_gpio) == GPIOF_DIR_IN)
> + gpiod_get_direction(pb->enable_gpio) != GPIOF_DIR_OUT)
> gpiod_direction_output(pb->enable_gpio, 1);
>
> pb->power_supply = devm_regulator_get(&pdev->dev, "power");
>

2017-03-24 16:43:58

by Daniel Thompson

Subject: Re: [PATCH] backlight: pwm_bl: Fix GPIO out for unimplemented .get_direction()

On 24/03/17 16:42, Daniel Thompson wrote:
> On 22/03/17 17:21, Geert Uytterhoeven wrote:
>> Commit 7613c922315e308a ("backlight: pwm_bl: Move the checks for initial
>> power state to a separate function") not just moved some code, but made
>> slight changes in semantics.
>>
>> If a gpiochip doesn't implement the optional .get_direction() callback,
>> gpiod_get_direction always returns -EINVAL, which is never equal to
>> GPIOF_DIR_IN, leading to the GPIO not being configured for output.
>>
>> To avoid this, invert the test and check for not GPIOF_DIR_OUT instead,
>> like the original code did.
>>
>> This restores the display on r8a7740/armadillo.
>>
>> Fixes: 7613c922315e308a ("backlight: pwm_bl: Move the checks for
>> initial power state to a separate function")
>> Signed-off-by: Geert Uytterhoeven <[email protected]>
>
> Acked-by: Daniel Thommpson <[email protected]>

Actually, it would be better if there only one m...

Acked-by: Daniel Thompson <[email protected]>


Daniel.

>
>
>> ---
>> drivers/video/backlight/pwm_bl.c | 7 ++++---
>> 1 file changed, 4 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/video/backlight/pwm_bl.c
>> b/drivers/video/backlight/pwm_bl.c
>> index d7efcb632f7d9dde..002f1ce22bd02032 100644
>> --- a/drivers/video/backlight/pwm_bl.c
>> +++ b/drivers/video/backlight/pwm_bl.c
>> @@ -297,14 +297,15 @@ static int pwm_backlight_probe(struct
>> platform_device *pdev)
>> }
>>
>> /*
>> - * If the GPIO is configured as input, change the direction to
>> output
>> - * and set the GPIO as active.
>> + * 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.
>> */
>> if (pb->enable_gpio &&
>> - gpiod_get_direction(pb->enable_gpio) == GPIOF_DIR_IN)
>> + gpiod_get_direction(pb->enable_gpio) != GPIOF_DIR_OUT)
>> gpiod_direction_output(pb->enable_gpio, 1);
>>
>> pb->power_supply = devm_regulator_get(&pdev->dev, "power");
>>
>

2017-03-27 14:28:00

by Lee Jones

Subject: Re: [PATCH] backlight: pwm_bl: Fix GPIO out for unimplemented .get_direction()

On Fri, 24 Mar 2017, Daniel Thompson wrote:

> On 24/03/17 16:42, Daniel Thompson wrote:
> > On 22/03/17 17:21, Geert Uytterhoeven wrote:
> > > Commit 7613c922315e308a ("backlight: pwm_bl: Move the checks for initial
> > > power state to a separate function") not just moved some code, but made
> > > slight changes in semantics.
> > >
> > > If a gpiochip doesn't implement the optional .get_direction() callback,
> > > gpiod_get_direction always returns -EINVAL, which is never equal to
> > > GPIOF_DIR_IN, leading to the GPIO not being configured for output.
> > >
> > > To avoid this, invert the test and check for not GPIOF_DIR_OUT instead,
> > > like the original code did.
> > >
> > > This restores the display on r8a7740/armadillo.
> > >
> > > Fixes: 7613c922315e308a ("backlight: pwm_bl: Move the checks for
> > > initial power state to a separate function")
> > > Signed-off-by: Geert Uytterhoeven <[email protected]>
> >
> > Acked-by: Daniel Thommpson <[email protected]>
>
> Actually, it would be better if there only one m...
>
> Acked-by: Daniel Thompson <[email protected]>

You probably don't want to be typing out your Acks manually every
time. Can you set a key combination in your editor?

> > > ---
> > > drivers/video/backlight/pwm_bl.c | 7 ++++---
> > > 1 file changed, 4 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/drivers/video/backlight/pwm_bl.c
> > > b/drivers/video/backlight/pwm_bl.c
> > > index d7efcb632f7d9dde..002f1ce22bd02032 100644
> > > --- a/drivers/video/backlight/pwm_bl.c
> > > +++ b/drivers/video/backlight/pwm_bl.c
> > > @@ -297,14 +297,15 @@ static int pwm_backlight_probe(struct
> > > platform_device *pdev)
> > > }
> > >
> > > /*
> > > - * If the GPIO is configured as input, change the direction to
> > > output
> > > - * and set the GPIO as active.
> > > + * 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.
> > > */
> > > if (pb->enable_gpio &&
> > > - gpiod_get_direction(pb->enable_gpio) == GPIOF_DIR_IN)
> > > + gpiod_get_direction(pb->enable_gpio) != GPIOF_DIR_OUT)
> > > gpiod_direction_output(pb->enable_gpio, 1);
> > >
> > > pb->power_supply = devm_regulator_get(&pdev->dev, "power");
> > >
> >
>

--
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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