Re: [PATCH 2/2] gpio: rcar: Fine-grained Runtime PM support

[Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>]

Hi Niklas,

On Friday 09 Dec 2016 00:15:51 Niklas Söderlund wrote:
> On 2016-12-08 23:40:42 +0200, Laurent Pinchart wrote:
> > On Thursday 08 Dec 2016 18:32:28 Niklas Söderlund wrote:
> >> From: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
> >> 
> >> Currently gpio modules are runtime-resumed at probe time. This means the
> >> gpio module will be active all the time (except during system suspend,
> >> if not configured as a wake-up source).
> >> 
> >> While an R-Car Gen2 gpio module retains pins configured for output at
> >> the requested level while put in standby mode, gpio register cannot be
> >> accessed while suspended.  Unfortunately pm_runtime_get_sync() cannot be
> >> called from all contexts where gpio register access is needed. Hence
> >> move the Runtime PM handling from probe/remove time to gpio request/free
> >> time, which is probably the best we can do.
> >> 
> >> On r8a7791/koelsch, gpio modules 0, 1, 3, and 4 are now suspended during
> >> normal use (gpio2 is used for LEDs and regulators, gpio5 for keys, gpio6
> >> for SD-Card CD & WP, gpio7 for keys and regulators).
> >> 
> >> Signed-off-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
> >> [Niklas: s/gpio_to_priv(chip)/gpiochip_get_data(chip)/]
> > 
> > Just curious, what's the rationale for this ?
> 
> This was changed for the whole driver after the original patch was
> applied (at the time of change the patch was not yet reverted), see [1].
> I needed to update this when I resurrected the patch, maybe I could have
> been more clever and reverted the revert patch but this felt cleaner, if
> it's better to do it the other way around and revert a revert please let
> me know so I can do so in the future.

No, this is fine. I'm a bit dubious about [1] given that it consumes more CPU 
cycles without any benefit as far as I can see. Maybe I can't see far enough 
though, Linus Walleij could prove me wrong :-)

> [1] c7b6f457cb53bcee ("gpio: rcar: use gpiochip data pointer").

-- 
Regards,

Laurent Pinchart

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