[PATCH 1/8] mmc: dt: pwrseq-simple: Invent power-off-delay-us

[Rob Herring]

On Mon, May 15, 2017 at 6:08 AM, Ulf Hansson <ulf.hansson at linaro.org> wrote:
> On 12 May 2017 at 22:03, Rob Herring <robh at kernel.org> wrote:
>> On Mon, May 08, 2017 at 06:21:10PM +0200, Ulf Hansson wrote:
>>> During power off, after the GPIO pin has been asserted, some devices like
>>> the Wifi chip from TI, Wl18xx, needs a delay before the host continues with
>>> clock gating and turning off regulators as to follow a graceful shutdown
>>> sequence.
>>>
>>> Therefore invent an optional power-off-delay-us DT binding for
>>> mmc-pwrseq-simple, to allow us to support this constraint.
>>
>> Do you really need this to be programmable per device. A delay is not
>> going to hurt devices that don't need it.
>
> Well, that depends on what "hurt" means. The device would still be
> properly shut down, only that it would take unnecessary longer to do
> so.
>
> I think the problem here, is that this delay may also affect system
> suspend/resume time of the device, if the device powers off/on in this
> sequence.

I was assuming that given you changed the units the time was small
enough to not be significant.

>> Sorry, but this is exactly what I don't like about "simple" bindings:
>> adding one property at a time.
>
> I understand you opinion, which in the end is a matter of taste/flavor.

It's more than that. The problem is you would end up with a different
binding if everything is defined up front versus reviewing one
addition at a time.

To give a trivial example here, now we have power on and off times in
different units and if I was reviewing them together I would say make
them both usec. That example is mostly taste, but different units also
makes it more error prone for the dts writer.

> However, for me this just follows the existing approach - and suddenly
> say no to this, doesn't really seems right either.

I never said no.

Rob