[PATCH RFC 1/4] ARM: bcm2835: remove sdhci pins from GPIO pinctrl

[swarren@wwwdotorg.org (Stephen Warren)]

On 12/05/2015 02:12 AM, Stefan Wahren wrote:
> 
>> Stephen Warren <swarren@wwwdotorg.org> hat am 2. Dezember 2015 um 04:40
>> geschrieben:
>>
>>
>> On 11/19/2015 09:06 AM, Stefan Wahren wrote:
>>> Currently the pins alt3 (sdhci) are assigned to GPIO pinctrl.
>>> This is bad because a user could export it to sysfs and break
>>> sdhci. In order to avoid that remove those pins from GPIO pintrl.
>>
>>> diff --git a/arch/arm/boot/dts/bcm2835-rpi-a-plus.dts
>>> b/arch/arm/boot/dts/bcm2835-rpi-a-plus.dts
>>
>>> &gpio {
>>> - pinctrl-0 = <&gpioout &alt0 &i2s_alt0 &alt3>;
>>> + pinctrl-0 = <&gpioout &alt0 &i2s_alt0>;
>>
>> This doesn't make sense. The current DT content is configuring those
>> pins as SDHCI, not as GPIO. Admitedly this is redundant since the
>> firmware and/or bootloader already did this in order to boot the system,
>> but irrespective, the current DT causes no issues. Removing the pinctrl
>> setting should not influence whether the pins can be exported via GPIO
>> sysfs either.
> 
> You are right. 
> 
> Is it generally possible to avoid the GPIO sysfs export for SDHCI pins? 
> Is it an issue of pinctrl-bcm2835?

I believe this same issue exists on all platforms where GPIO pins can be
mux'd onto the same pins as other functions.