Re: [PATCH v3] mmc: sdhci-xenon: Add Xenon SDHCI specific system-level PM support

[Jisheng Zhang <jszhang@marvell.com>]

Hi Ulf,

On Thu, 13 Jul 2017 11:18:32 +0200 Ulf Hansson wrote:

> On 13 July 2017 at 00:16, Zhoujie Wu <zjwu@marvell.com> wrote:
> > From: Hu Ziji <huziji@marvell.com>
> >
> > Add Xenon specific system-level suspend and resume support.
> > Especially during resume, re-configure Xenon specific registers
> > since registers setting will be lost in suspend if Xenon is power off.  
> 
> I recommend to start with deploying runtime PM support instead of
> system PM support. Then on top of such change, you should make use of
> the runtime PM centric path to get system sleep support for "free"
> (and thus all the nice benefits).

I'm not sure whether runtime PM is useful for xenon case. The xenon HW
support ACG(Auto Clock Gating) and SDCLK-Off-While-Idle features, that's
to say we even don't need to do anything but achieve the runtime PM gains.

Thanks,
Jisheng

> 
> Please have a look at sdhci-of-at91 for a good reference.
> Regarding sdhci-of-at91, there is currently a patch [1], which adds
> dealing with restoring context of registers after a system resume.
> Similar to what you need.
> 
> Kind regards
> Uffe
> 
> [1]
> https://patchwork.kernel.org/patch/9837951/
> 
> [...]
> 
> Kind regards
> Uffe