Re: linux-next regression caused by "gpiolib: request the gpio before querying its direction"

[Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>]

On Wed, Aug 30, 2017 at 6:24 PM, jmondi <jacopo@xxxxxxxxxx> wrote:
> On Wed, Aug 30, 2017 at 04:32:55PM +0200, Thomas Petazzoni wrote:
>> On Wed, 30 Aug 2017 09:22:55 -0500, Timur Tabi wrote:
>> > No, that's it.  The question is, what exactly should the 'request'
>> > function do?  Should it be modifying the hardware to satisfy the
>> > request?  When I wrote my patch, I assumed that it wouldn't.  I thought
>> > that request simply answered the question, "can I touch this GPIO"?
>>
>> No, it also muxes the pin in GPIO, and you can see the "reference"
>> implementation pinctrl-single also does it.
>>
>> Let's see what Linus W. has to say about the semantic of the "request"
>> operation.
>>
>> But if we change the semantic of "request" to no longer mux the hardware
>> as GPIO, then you will also have regressions, because there are plenty
>> of GPIOs that are requested, but not explicitly muxed as GPIOs in the
>> DT, precisely because today requesting a GPIO is sufficient to have it
>> re-muxed as GPIO at the pinctrl level.
>
> Just to point out one of Renesas' pin controller devices seems to
> suffer from the same problem, introduced by Timur's commit
>
> https://www.spinics.net/lists/linux-renesas-soc/msg17647.html
>
> This is indeed caused by the "request" introduced by the above said
> commit, that in rza1 pincontroller, actually muxes the requested
> pin as GPIO.

To clarify: which causes havoc if that pin is used as e.g. an SDRAM
address line.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

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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