[PATCH 2/2] arm64: dts: rockchip: add eMMC's power domain support for rk3399

[Doug Anderson]

Hi,

On Wed, Aug 31, 2016 at 7:29 PM, Ziyuan Xu <xzy.xu at rock-chips.com> wrote:
>> This is fine to pick up _only_ if you don't care about suspend/resume.
>> If you care about suspend/resume then someone needs to first write a
>> patch that will re-init all "corecfg" values after power is turned on.
>
>
> Do you mean corecfg_clockmultiplier and corecfg_baseclkfreq, if yes, we
> don't need to strore/re-init it after resume.
> corecfg_clockmultiplier is only used to fetch host->clk_mul, and
> host->clk_mul has been a fixed value at run-time, unless driver unbind.
> The same as corecfg_clockmultiplier, corecfg_baseclkfreq is used to check
> the xin_clk at probe time, we don't reference it at run-time.
> BTW, I have tested suspend/resume on rk3399 prior to this sumbit, eMMC works
> fine.

I guess I don't actually know how the corecfg_clockmultiplier and
corecfg_baseclkfreq fields are actually used, but I presume that they
actually do something useful and aren't used to just communicate back
to software?

I know that:

1. If I don't pick this patch and I suspend/resume,
corecfg_clockmultiplier and corecfg_baseclkfreq are still fine after
suspend / resume.

2. If I do pick this patch and I suspend/resume,
corecfg_clockmultiplier and corecfg_baseclkfreq are wrong after
suspend/resume (tested by reading /dev/mem directly from userspace
after suspend/resume).


Are you saying that it is unimportant that corecfg_clockmultiplier and
corecfg_baseclkfreq are wrong?

>> Technically I think this should probably use "pm runtime" and not
>> normal suspend/resume hooks.  Any time we end up pm runtime suspended
>> then I think our power will go off (because of genpd?) and we need to
>> restore values.
>
>
> I understand your consideration. BUT genpd is in charge of on/off pd if the
> corresponding device node has "power-domains" property. RPM is unnecessary
> for this situation, we will not use autosuspend, right?
>
> @shawn, what's your opinion?

I haven't dug.  If Runtime PM isn't enabled for sdhci-of-arasan then I
guess we can just worry about suspend/resume, though.

-Doug