[PATCH] gpio: pca953x: Don't flip bits on PCA957x GPIO expanders when probing them.

[PATCH] gpio: pca953x: Don't flip bits on PCA957x GPIO expanders when probing them.

[Graeme Smecher]

The pca957x driver supports a handful of I2C GPIO expanders from NXP, Maxim,
and TI. For the PCA9574 and PCA9575 devices only, the driver resets the GPIO
level and direction in the pca957x_probe function. This seems like the wrong
thing to do, since it can cause hardware bit twiddles during warm reboots when
the chip state and reset values don't match.

This kind of initialization is best left upstream (in a bootloader) or
downstream (in userspace). It's also an inconsistency across devices supported
by this driver.

This patch is NOT boot-tested: the SoC I'm  using is stuck on 2.6.37, and the
patch doesn't apply trivially.

Signed-off-by: Graeme Smecher <gsmecher@threespeedlogic.com>
Acked-by: Haojian Zhuang <haojian.zhuang@gmail.com>
---
 drivers/gpio/gpio-pca953x.c |   11 -----------
 1 file changed, 11 deletions(-)

diff --git a/drivers/gpio/gpio-pca953x.c b/drivers/gpio/gpio-pca953x.c
index cdd1aa1..6e48c07 100644
--- a/drivers/gpio/gpio-pca953x.c
+++ b/drivers/gpio/gpio-pca953x.c
@@ -683,17 +683,6 @@ static int device_pca957x_init(struct pca953x_chip *chip, u32 invert)
 	int ret;
 	u8 val[MAX_BANK];
 
-	/* Let every port in proper state, that could save power */
-	memset(val, 0, NBANK(chip));
-	pca953x_write_regs(chip, PCA957X_PUPD, val);
-	memset(val, 0xFF, NBANK(chip));
-	pca953x_write_regs(chip, PCA957X_CFG, val);
-	memset(val, 0, NBANK(chip));
-	pca953x_write_regs(chip, PCA957X_OUT, val);
-
-	ret = pca953x_read_regs(chip, PCA957X_IN, val);
-	if (ret)
-		goto out;
 	ret = pca953x_read_regs(chip, PCA957X_OUT, chip->reg_output);
 	if (ret)
 		goto out;
-- 
1.7.10.4

Re: [PATCH] gpio: pca953x: Don't flip bits on PCA957x GPIO expanders when probing them.

[Linus Walleij]

On Fri, Sep 13, 2013 at 11:41 PM, Graeme Smecher
<gsmecher@threespeedlogic.com> wrote:

> The pca957x driver supports a handful of I2C GPIO expanders from NXP, Maxim,
> and TI. For the PCA9574 and PCA9575 devices only, the driver resets the GPIO
> level and direction in the pca957x_probe function. This seems like the wrong
> thing to do, since it can cause hardware bit twiddles during warm reboots when
> the chip state and reset values don't match.
>
> This kind of initialization is best left upstream (in a bootloader) or
> downstream (in userspace). It's also an inconsistency across devices supported
> by this driver.
>
> This patch is NOT boot-tested: the SoC I'm  using is stuck on 2.6.37, and the
> patch doesn't apply trivially.
>
> Signed-off-by: Graeme Smecher <gsmecher@threespeedlogic.com>
> Acked-by: Haojian Zhuang <haojian.zhuang@gmail.com>

Looks like you're deleting code from Gregory CLEMENT,
Gregory what do you say about this?

Yours,
Linus Walleij

Re: [PATCH] gpio: pca953x: Don't flip bits on PCA957x GPIO expanders when probing them.

[Gregory CLEMENT]

Hi Linus,

On 20/09/2013 22:24, Linus Walleij wrote:
> On Fri, Sep 13, 2013 at 11:41 PM, Graeme Smecher
> <gsmecher@threespeedlogic.com> wrote:
> 
>> The pca957x driver supports a handful of I2C GPIO expanders from NXP, Maxim,
>> and TI. For the PCA9574 and PCA9575 devices only, the driver resets the GPIO
>> level and direction in the pca957x_probe function. This seems like the wrong
>> thing to do, since it can cause hardware bit twiddles during warm reboots when
>> the chip state and reset values don't match.
>>
>> This kind of initialization is best left upstream (in a bootloader) or
>> downstream (in userspace). It's also an inconsistency across devices supported
>> by this driver.
>>
>> This patch is NOT boot-tested: the SoC I'm  using is stuck on 2.6.37, and the
>> patch doesn't apply trivially.
>>
>> Signed-off-by: Graeme Smecher <gsmecher@threespeedlogic.com>
>> Acked-by: Haojian Zhuang <haojian.zhuang@gmail.com>
> 
> Looks like you're deleting code from Gregory CLEMENT,
> Gregory what do you say about this?

Thanks to point me this patch, I didn't have noticed it.
The code being removed is mine because I change it to take care of the
multiple bankd. I didn't change the functionality. The original code
was from Haojian Zhuang so as he gave his acked-by it should be fine.

However could you wait for until the end of this week end, to let me test
it on a real hardware?

Thanks,

Gregory

-- 
Gregory Clement, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com

Re: [PATCH] gpio: pca953x: Don't flip bits on PCA957x GPIO expanders when probing them.

[Linus Walleij]

On Fri, Sep 20, 2013 at 10:37 PM, Gregory CLEMENT
<gregory.clement@free-electrons.com> wrote:

> However could you wait for until the end of this week end, to let me test
> it on a real hardware?

Sure, no hurry.

Yours,
Linus Walleij

Re: [PATCH] gpio: pca953x: Don't flip bits on PCA957x GPIO expanders when probing them.

[Gregory CLEMENT]

Hi,

On 20/09/2013 23:06, Linus Walleij wrote:
> On Fri, Sep 20, 2013 at 10:37 PM, Gregory CLEMENT
> <gregory.clement@free-electrons.com> wrote:
> 
>> However could you wait for until the end of this week end, to let me test
>> it on a real hardware?
> 
> Sure, no hurry.
> 

I tested the patch using the GPIO box connected to the Mirabox and I
didn't see any regression. So you can add my:

Tested-by: Gregory CLEMENT <gregory.clement@free-electrons.com>

Thanks,

> Yours,
> Linus Walleij
> 


-- 
Gregory Clement, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com

Re: [PATCH] gpio: pca953x: Don't flip bits on PCA957x GPIO expanders when probing them.

[Linus Walleij]

On Fri, Sep 13, 2013 at 11:41 PM, Graeme Smecher
<gsmecher@threespeedlogic.com> wrote:

> The pca957x driver supports a handful of I2C GPIO expanders from NXP, Maxim,
> and TI. For the PCA9574 and PCA9575 devices only, the driver resets the GPIO
> level and direction in the pca957x_probe function. This seems like the wrong
> thing to do, since it can cause hardware bit twiddles during warm reboots when
> the chip state and reset values don't match.
>
> This kind of initialization is best left upstream (in a bootloader) or
> downstream (in userspace). It's also an inconsistency across devices supported
> by this driver.
>
> This patch is NOT boot-tested: the SoC I'm  using is stuck on 2.6.37, and the
> patch doesn't apply trivially.
>
> Signed-off-by: Graeme Smecher <gsmecher@threespeedlogic.com>
> Acked-by: Haojian Zhuang <haojian.zhuang@gmail.com>

Patch applied with Gregory's Tested-by tag!

Yours,
Linus Walleij

Re: [PATCH] gpio: pca953x: Don't flip bits on PCA957x GPIO expanders when probing them.

[Graeme Smecher]

Hi,

On 23/09/13 06:57 AM, Linus Walleij wrote:
> On Fri, Sep 13, 2013 at 11:41 PM, Graeme Smecher
> <gsmecher@threespeedlogic.com>  wrote:
>
>> The pca957x driver supports a handful of I2C GPIO expanders from NXP, Maxim,
>> and TI. For the PCA9574 and PCA9575 devices only, the driver resets the GPIO
>> level and direction in the pca957x_probe function. This seems like the wrong
>> thing to do, since it can cause hardware bit twiddles during warm reboots when
>> the chip state and reset values don't match.
>>
>> This kind of initialization is best left upstream (in a bootloader) or
>> downstream (in userspace). It's also an inconsistency across devices supported
>> by this driver.
>>
>> This patch is NOT boot-tested: the SoC I'm  using is stuck on 2.6.37, and the
>> patch doesn't apply trivially.
>>
>> Signed-off-by: Graeme Smecher<gsmecher@threespeedlogic.com>
>> Acked-by: Haojian Zhuang<haojian.zhuang@gmail.com>
> Patch applied with Gregory's Tested-by tag!

Thanks all!

cheers,
Graeme