[PATCH] cs5535_gpio: gpio_chip.get should return the input value

[PATCH] cs5535_gpio: gpio_chip.get should return the input value

[Ben Gardner]

The gpio_chip.get() function for the CS5535 GPIO driver currently returns the
output value instead of the input value.
This patch changes it to return the input value.

Signed-off-by: Ben Gardner <gardner.ben@gmail.com>
---
--- linux-2.6.33-rc8.orig/drivers/gpio/cs5535-gpio.c
+++ linux-2.6.33-rc8/drivers/gpio/cs5535-gpio.c
@@ -154,7 +154,7 @@

 static int chip_gpio_get(struct gpio_chip *chip, unsigned offset)
 {
-	return cs5535_gpio_isset(offset, GPIO_OUTPUT_VAL);
+	return cs5535_gpio_isset(offset, GPIO_READ_BACK);
 }

 static void chip_gpio_set(struct gpio_chip *chip, unsigned offset, int val)

Re: [PATCH] cs5535_gpio: gpio_chip.get should return the input value

[Andrew Morton]

On Tue, 23 Feb 2010 16:55:17 -0600 Ben Gardner <gardner.ben@gmail.com> wrote:

> The gpio_chip.get() function for the CS5535 GPIO driver currently returns the
> output value instead of the input value.
> This patch changes it to return the input value.
> 
> Signed-off-by: Ben Gardner <gardner.ben@gmail.com>
> ---
> --- linux-2.6.33-rc8.orig/drivers/gpio/cs5535-gpio.c
> +++ linux-2.6.33-rc8/drivers/gpio/cs5535-gpio.c
> @@ -154,7 +154,7 @@
> 
>  static int chip_gpio_get(struct gpio_chip *chip, unsigned offset)
>  {
> -	return cs5535_gpio_isset(offset, GPIO_OUTPUT_VAL);
> +	return cs5535_gpio_isset(offset, GPIO_READ_BACK);
>  }
> 
>  static void chip_gpio_set(struct gpio_chip *chip, unsigned offset, int val)

<presses F10>

What were the user-visible effects of this bug?

Re: [PATCH] cs5535_gpio: gpio_chip.get should return the input value

[Andres Salomon]

On Tue, 23 Feb 2010 16:55:17 -0600
Ben Gardner <gardner.ben@gmail.com> wrote:

> The gpio_chip.get() function for the CS5535 GPIO driver currently
> returns the output value instead of the input value.
> This patch changes it to return the input value.
> 
> Signed-off-by: Ben Gardner <gardner.ben@gmail.com>
> ---
> --- linux-2.6.33-rc8.orig/drivers/gpio/cs5535-gpio.c
> +++ linux-2.6.33-rc8/drivers/gpio/cs5535-gpio.c
> @@ -154,7 +154,7 @@
> 
>  static int chip_gpio_get(struct gpio_chip *chip, unsigned offset)
>  {
> -	return cs5535_gpio_isset(offset, GPIO_OUTPUT_VAL);
> +	return cs5535_gpio_isset(offset, GPIO_READ_BACK);
>  }
> 
>  static void chip_gpio_set(struct gpio_chip *chip, unsigned offset,
> int val)

Hm, you're probably right.  Of course this breaks cs5535audio_olpc.c,
since the GPIO isn't marked bidirectional (only output is enabled).
I'll follow up w/ a patch.

Acked-by: Andres Salomon <dilinger@collabora.co.uk>

[PATCH] OLPC: ALSA: fix cs5535audio's MIC GPIO to enable input

[Andres Salomon]

Previously the MIC GPIO was set to output mode, and when checking the status
after setting it we were checking OUTPUT_VAL.  This worked, though I'm not
quite sure why.  Instead, if we actually check the READ_BACK value, it
doesn't work unless the GPIO is in bidirectional mode.  Thus, enable
input mode as well.

Signed-off-by: Andres Salomon <dilinger@collabora.co.uk>
---
 sound/pci/cs5535audio/cs5535audio_olpc.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/sound/pci/cs5535audio/cs5535audio_olpc.c b/sound/pci/cs5535audio/cs5535audio_olpc.c
index 50da49b..f5574f2 100644
--- a/sound/pci/cs5535audio/cs5535audio_olpc.c
+++ b/sound/pci/cs5535audio/cs5535audio_olpc.c
@@ -157,6 +157,7 @@ int __devinit olpc_quirks(struct snd_card *card, struct snd_ac97 *ac97)
 		return -EIO;
 	}
 	gpio_direction_output(OLPC_GPIO_MIC_AC, 0);
+	gpio_direction_input(OLPC_GPIO_MIC_AC);
 
 	/* drop the original AD1888 HPF control */
 	memset(&elem, 0, sizeof(elem));
-- 
1.5.6.5

Re: [PATCH] cs5535_gpio: gpio_chip.get should return the input value

[Ben Gardner]

>> --- linux-2.6.33-rc8.orig/drivers/gpio/cs5535-gpio.c
>> +++ linux-2.6.33-rc8/drivers/gpio/cs5535-gpio.c
>> @@ -154,7 +154,7 @@
>>
>>  static int chip_gpio_get(struct gpio_chip *chip, unsigned offset)
>>  {
>> -     return cs5535_gpio_isset(offset, GPIO_OUTPUT_VAL);
>> +     return cs5535_gpio_isset(offset, GPIO_READ_BACK);
>>  }
>>
>>  static void chip_gpio_set(struct gpio_chip *chip, unsigned offset, int val)
>
> <presses F10>
>
> What were the user-visible effects of this bug?

The user-visible effects were that the input didn't work.
I use the CS5535 chip in a custom board that uses GPIO 25 and 26 as
voltage monitoring inputs (external voltage comparators).
Since the char-based cs5535-gpio is now deprecated, I'm trying out the
gpio driver.
I export the GPIO pins via sysfs to access them from user-space.
Reading the 'value' member didn't reflect the input.

Personally, I would prefer a separate sysfs entry for the output and
the input, since the GPIO pins can be both outputs and inputs, but
that would require a gpiolib change.
Since there doesn't appear to be a gpio maintainer, any change to that
might be tricky.

Ben

Re: [PATCH] cs5535_gpio: gpio_chip.get should return the input value

[Andrew Morton]

On Wed, 24 Feb 2010 21:52:07 -0600 Ben Gardner <gardner.ben@gmail.com> wrote:

> >> --- linux-2.6.33-rc8.orig/drivers/gpio/cs5535-gpio.c
> >> +++ linux-2.6.33-rc8/drivers/gpio/cs5535-gpio.c
> >> @@ -154,7 +154,7 @@
> >>
> >> __static int chip_gpio_get(struct gpio_chip *chip, unsigned offset)
> >> __{
> >> - __ __ return cs5535_gpio_isset(offset, GPIO_OUTPUT_VAL);
> >> + __ __ return cs5535_gpio_isset(offset, GPIO_READ_BACK);
> >> __}
> >>
> >> __static void chip_gpio_set(struct gpio_chip *chip, unsigned offset, int val)
> >
> > <presses F10>
> >
> > What were the user-visible effects of this bug?
> 
> The user-visible effects were that the input didn't work.
> I use the CS5535 chip in a custom board that uses GPIO 25 and 26 as
> voltage monitoring inputs (external voltage comparators).
> Since the char-based cs5535-gpio is now deprecated, I'm trying out the
> gpio driver.
> I export the GPIO pins via sysfs to access them from user-space.
> Reading the 'value' member didn't reflect the input.

OK, then in that case we'd want to backport this into 2.6.33.x and
perhaps earlier?

> Personally, I would prefer a separate sysfs entry for the output and
> the input, since the GPIO pins can be both outputs and inputs, but
> that would require a gpiolib change.
> Since there doesn't appear to be a gpio maintainer, any change to that
> might be tricky.

Eh, we can cope.  Propose a patch and cc lots of people..

Re: [PATCH] cs5535_gpio: gpio_chip.get should return the input value

[Ben Gardner]

>> > What were the user-visible effects of this bug?
>>
>> The user-visible effects were that the input didn't work.
>> I use the CS5535 chip in a custom board that uses GPIO 25 and 26 as
>> voltage monitoring inputs (external voltage comparators).
>> Since the char-based cs5535-gpio is now deprecated, I'm trying out the
>> gpio driver.
>> I export the GPIO pins via sysfs to access them from user-space.
>> Reading the 'value' member didn't reflect the input.
>
> OK, then in that case we'd want to backport this into 2.6.33.x and
> perhaps earlier?

It looks like the driver was added 15 Dec 2009, so it doesn't look
like it existed in an earlier kernel.

>> Personally, I would prefer a separate sysfs entry for the output and
>> the input, since the GPIO pins can be both outputs and inputs, but
>> that would require a gpiolib change.
>> Since there doesn't appear to be a gpio maintainer, any change to that
>> might be tricky.
>
> Eh, we can cope.  Propose a patch and cc lots of people..

Will do.

Thanks,
Ben

Re: [PATCH] cs5535_gpio: gpio_chip.get should return the input value

[Andres Salomon]

On Wed, 24 Feb 2010 22:16:43 -0600
Ben Gardner <gardner.ben@gmail.com> wrote:

> >> > What were the user-visible effects of this bug?
> >>
> >> The user-visible effects were that the input didn't work.
> >> I use the CS5535 chip in a custom board that uses GPIO 25 and 26 as
> >> voltage monitoring inputs (external voltage comparators).
> >> Since the char-based cs5535-gpio is now deprecated, I'm trying out
> >> the gpio driver.
> >> I export the GPIO pins via sysfs to access them from user-space.
> >> Reading the 'value' member didn't reflect the input.
> >
> > OK, then in that case we'd want to backport this into 2.6.33.x and
> > perhaps earlier?
> 
> It looks like the driver was added 15 Dec 2009, so it doesn't look
> like it existed in an earlier kernel.

But it should definitely be added to 2.6.33.y.

Re: [PATCH] OLPC: ALSA: fix cs5535audio's MIC GPIO to enable input

[Ben Gardner]

Hi Andres,

> Previously the MIC GPIO was set to output mode, and when checking the status
> after setting it we were checking OUTPUT_VAL.  This worked, though I'm not
> quite sure why. Instead, if we actually check the READ_BACK value, it
> doesn't work unless the GPIO is in bidirectional mode.  Thus, enable
> input mode as well.

The cs5535-gpio driver was reading output value, not the sensed input value.
When that was fixed, this OLPC code failed because the input wasn't
enabled, so the gpio_get_value() call didn't return anything useful.
At reset the CS5535/6 GPIOs have both input and output disabled.

> Signed-off-by: Andres Salomon <dilinger@collabora.co.uk>
> ---
>  sound/pci/cs5535audio/cs5535audio_olpc.c |    1 +
>  1 files changed, 1 insertions(+), 0 deletions(-)
>
> diff --git a/sound/pci/cs5535audio/cs5535audio_olpc.c b/sound/pci/cs5535audio/cs5535audio_olpc.c
> index 50da49b..f5574f2 100644
> --- a/sound/pci/cs5535audio/cs5535audio_olpc.c
> +++ b/sound/pci/cs5535audio/cs5535audio_olpc.c
> @@ -157,6 +157,7 @@ int __devinit olpc_quirks(struct snd_card *card, struct snd_ac97 *ac97)
>                return -EIO;
>        }
>        gpio_direction_output(OLPC_GPIO_MIC_AC, 0);
> +       gpio_direction_input(OLPC_GPIO_MIC_AC);
>
>        /* drop the original AD1888 HPF control */
>        memset(&elem, 0, sizeof(elem));

This will only work because the cs5535-gpio driver and gpiolib are
both 'broken'.

The problem with gpiolib is that it only allows a GPIO pin to be
either an input or output, but not both.
It has two separate functions to configure the direction
(gpio_direction_input/gpio_direction_output), where one should do (ie,
gpio_set_direction).
>From what I can tell, when direction_input() is called, the GPIO chip
is expected to disable the output and enable the input. If that really
occurred, then the above code would still be broken.

The cs5535-gpio driver doesn't follow that input-or-output convention.
It never disables the direction that wasn't requested.

I'm working on a gpiolib patch that will combine gpio_direction_output
and gpio_direction_input into one function.  That would enable the
above driver to be 'obviously correct'.

Ben

Re: [PATCH] OLPC: ALSA: fix cs5535audio's MIC GPIO to enable input

[Andres Salomon]

On Fri, 26 Feb 2010 11:47:35 -0600
Ben Gardner <gardner.ben@gmail.com> wrote:

[...]
> 
> I'm working on a gpiolib patch that will combine gpio_direction_output
> and gpio_direction_input into one function.  That would enable the
> above driver to be 'obviously correct'.
> 

Cool.  I'm happy to help convert drivers if you want the help.

Re: [PATCH] OLPC: ALSA: fix cs5535audio's MIC GPIO to enable input

[Ben Gardner]

>> I'm working on a gpiolib patch that will combine gpio_direction_output
>> and gpio_direction_input into one function.  That would enable the
>> above driver to be 'obviously correct'.
>
> Cool.  I'm happy to help convert drivers if you want the help.

I'm not one to turn down help.
Lets see how the proposed changes I just sent off are received and go
from there.

Ben

Re: [PATCH] OLPC: ALSA: fix cs5535audio's MIC GPIO to enable input

[Ben Gardner]

> Lets see how the proposed changes I just sent off are received and go
> from there.

Based on the feedback from the other gpio patches, I'd like to do the following:
1) drop this patch (olpc-alsa-fix-cs5535audios-mic-gpio-to-enable-input.patch)
2) drop the patch that caused this patch to be created
(cs5535_gpio-gpio_chipget-should-return-the-input-value.patch)
3) submit a new patch that contains the original change + the changes
needed to adjust input/output settings to follow the spirit of
gpiolib.

That way, there is one patch that fully fixes the issue and no window
where the OLPC MIC stuff is broken.

Ben

Re: [PATCH] OLPC: ALSA: fix cs5535audio's MIC GPIO to enable input

[Andres Salomon]

On Mon, 1 Mar 2010 08:55:44 -0600
Ben Gardner <gardner.ben@gmail.com> wrote:

> > Lets see how the proposed changes I just sent off are received and go
> > from there.
> 
> Based on the feedback from the other gpio patches, I'd like to do the following:
> 1) drop this patch (olpc-alsa-fix-cs5535audios-mic-gpio-to-enable-input.patch)
> 2) drop the patch that caused this patch to be created
> (cs5535_gpio-gpio_chipget-should-return-the-input-value.patch)
> 3) submit a new patch that contains the original change + the changes
> needed to adjust input/output settings to follow the spirit of
> gpiolib.
> 
> That way, there is one patch that fully fixes the issue and no window
> where the OLPC MIC stuff is broken.
> 

That'd be great, thanks!