Re: [PATCH] mmc: pwrseq: add support for Marvell SD8787 chip

From: Ulf Hansson
Date: Wed Nov 30 2016 - 09:40:10 EST

On 30 November 2016 at 14:11, Javier Martinez Canillas
<javier@xxxxxxxxxxxx> wrote:
> Hello Matt,
> On Tue, Nov 29, 2016 at 10:20 PM, Matt Ranostay
> <matt@xxxxxxxxxxxxxxxxxxx> wrote:
>> On Tue, Nov 29, 2016 at 9:13 AM, Javier Martinez Canillas
> [snip]
>>>> +- pwndn-gpio: contains a power down GPIO specifier.
>>>> +- reset-gpio: contains a reset GPIO specifier.
>>>> +
>>> I wonder if we really need a custom power sequence provider for just
>>> this SDIO WiFI chip though. AFAICT the only missing piece in
>>> mmc-pwrseq-simple is the power down GPIO property, so maybe
>>> mmc-pwrseq-simple could be extended instead to have an optional
>>> powerdown-gpios property and instead in the Marvell SD8787 DT binding
>>> can be mentioned which mmc-pwrseq-simple properties are required for
>>> the device.
>> The reason we didn't do that is we need delay between the two
>> assertions/desertions of GPIOs. It wouldn't seems good practice to
>> hack the pwrseq-simple for this...
> Yes, I noticed that. I wouldn't say that it would be a hack for the
> pwrseq-simple since it already has a "post-power-on-delay-ms" DT
> property, so AFAICT it would just be adding a "pre-power-on-delay-ms"
> property for your use case.
> It would also be more consistent since it would support a delay for
> pre and post power callbacks. It would also make you avoid hardcoding
> the 300 msec wait, in case other device has a similar need but with a
> different wait time.
> In summary, I think that devices having a power (or power down) and
> enable GPIO, and needing to wait between the GPIO toggling are common.
> So I would prefer to make pwrseq-simple usable for these instead of
> adding device specific power sequence providers. But it's just my
> opinion and not my call :-)

This is a good idea. Please try out this approach.


Kind regards