Re: [PATCH 1/2] mmc: core: allow a reset gpio to be configured.

Ulf Hansson
2014-11-28T11:56:35Z

On 8 November 2014 at 01:14, NeilBrown <neilb@suse.de> wrote:
> If the regulator supplying an SDIO device is shared
> with another device, the turning the regulator 'on' and 'off'
> will not actually cycle power and so will not reset
> the device.
>
> This is particularly a problem for some wi2si wireless modules which
> have a BT module on chip and can share power lines.
> Without the power-cycle, subsequent reset commands fail.
>
> So allow a 'reset' gpio to be specified. If provided, the
> line is asserted during power-up.

There have been several attempts to fix similar issues as this patch
does. The latest one I posted a few month ago, which wasn't accepted.
http://comments.gmane.org/gmane.linux.power-management.general/46635

There has also been some off-list discussions on especially how we
should describe this in DT and there were actually some consensus made
around that. Still I haven't seen any patches on the mailing lists.

So to summarize, I am really concerned that we keep having these power
sequence issues for SDIO devices and right now the discussion has been
on hold. I am considering to hack on it myself, since I am tired of
waiting. :-)

Regarding this patch, I don't intent to apply it.

Kind regards
Uffe