linux-kernel - Re: [PATCH v3 3/5] spi: sunxi: Add Allwinner A31 SPI controller driver

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Message-ID: <20140204110209.GQ22609@sirena.org.uk>
Date:	Tue, 4 Feb 2014 11:02:09 +0000
From:	Mark Brown <broonie@...nel.org>
To:	Maxime Ripard <maxime.ripard@...e-electrons.com>
Cc:	Mike Turquette <mturquette@...aro.org>,
	Emilio Lopez <emilio@...pez.com.ar>,
	linux-sunxi@...glegroups.com, linux-spi@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, kevin.z.m.zh@...il.com,
	sunny@...winnertech.com, shuge@...winnertech.com,
	zhuzhenhua@...winnertech.com, Kevin Hilman <khilman@...aro.org>
Subject: Re: [PATCH v3 3/5] spi: sunxi: Add Allwinner A31 SPI controller
 driver

On Tue, Feb 04, 2014 at 10:09:26AM +0100, Maxime Ripard wrote:
> On Tue, Feb 04, 2014 at 12:21:10AM +0000, Mark Brown wrote:

> > It isn't awesome, no.  Ideally the runtime PM code would do this but
> > then you couldn't ifdef the operations which as far as I can tell is the
> > main thing people want from disabling it and it gets complicated for
> > devices that genuinely do power up on startup so here we are.

> We discussed it with Kevin on IRC, and he suggested that we move that
> pm_runtime initialization to the SPI core, but I guess that would also
> mean that all drivers shouldn't ifdef the operations, so that the core
> can call the runtime_resume callback directly.

No, that's not going to be robust - it means drivers can't do any power
sequencing of their own.

> However, I don't really get why any driver should be doing so, since
> you still need these functions to at least to the device
> suspend/resume in the probe/remove, and you don't really want to
> duplicate the code.

I don't think it's particularly useful to support disabling runtime PM
in the first place but some drivers do different things when doing
runtime management to those they do on first init - for example there
may be additional steps that only need to be done during first power up.

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