[RFC PATCH v3] reset: Add a defer reset object to send board specific reset

[Maxime Ripard]

On Thu, Aug 14, 2014 at 11:36:38AM +0200, Philipp Zabel wrote:
> Hi Maxime,
> 
> Am Montag, den 11.08.2014, 19:33 +0200 schrieb Maxime Ripard:
> > > Mostly because Maxime and I seem to have a completely different opinion
> > > and nobody else argued one way or the other.
> > 
> > Yep, mostly because I don't see how a generic approach can work.
> > 
> > The existing reset-gpios property only provide the gpio to use, but
> > some informations are encoded in the driver, such as the reset
> > duration, or a reset sequence if any.
> 
> The driver should provide the duration.

How? This used to be in the code, and reset_control_reset doesn't take
such argument.

> I'd really like to see an example where sequencing is necessary.

Well, if you have several reset lines, the sequencing between each
might be important.

> I agree that as soon as things get significantly more complicated than
> pulsing a single GPIO, the reset-gpios binding is too limited.

While the generic reset bindings are perfect for that.

> Still, I'm not happy to mandate a separate gpio reset device for each
> reset line if most devices are simple enough for it to work without.

Well, it's pretty much already the case for other subsystems, such as
regulator.

I guess we can treat this as a legacy option, but allow the reset-gpio
code to be a full driver of its own, if we need more advanced use
cases?

> What about using reset-gpios for the majority of simple cases and have a
> separate gpio-reset-sequencer driver when multiple GPIO resets have to
> be timed?

I don't know. I feel like it should be in the driver itself, rather
than in a generic layer.

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
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