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

From: Doug Anderson <dianders@chromium.org>
To: Shawn Lin <shawn.lin@rock-chips.com>
Cc: "Elaine Zhang" <zhangqing@rock-chips.com>,
	"Rob Herring" <robh+dt@kernel.org>,
	"Heiko Stübner" <heiko@sntech.de>,
	"Ziyuan Xu" <xzy.xu@rock-chips.com>,
	"Ulf Hansson" <ulf.hansson@linaro.org>,
	"Mark Rutland" <mark.rutland@arm.com>,
	"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
	"Catalin Marinas" <catalin.marinas@arm.com>,
	"Xing Zheng" <zhengxing@rock-chips.com>,
	"Masahiro Yamada" <yamada.masahiro@socionext.com>,
	"Frank Wang" <frank.wang@rock-chips.com>,
	"Brian Norris" <briannorris@chromium.org>,
	"Will Deacon" <will.deacon@arm.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"open list:ARM/Rockchip SoC..."
	<linux-rockchip@lists.infradead.org>,
	"Jianqun Xu" <jay.xu@rock-chips.com>,
	"David Wu" <david.wu@rock-chips.com>,
	"Shunqian Zheng" <zhengsq@rock-chips.com>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>,
	"Caesar Wang" <wxt@rock-chips.com>
Subject: Re: [PATCH 2/2] arm64: dts: rockchip: add eMMC's power domain support for rk3399
Date: Wed, 31 Aug 2016 10:42:40 -0700	[thread overview]
Message-ID: <CAD=FV=W=LkVAm187hxp0Kbjxi5kSThwKnCMX+tr8SXQ-v_xQTQ@mail.gmail.com> (raw)
In-Reply-To: <ceba6a89-6945-58c5-62e4-7d842cfa2312@rock-chips.com>

Hi,

On Sun, Aug 28, 2016 at 8:25 PM, Shawn Lin <shawn.lin@rock-chips.com> wrote:
> On 2016/8/29 10:50, Elaine Zhang wrote:
>>
>>
>>
>> On 08/27/2016 11:05 PM, Shawn Lin wrote:
>>>
>>> On 2016/8/27 21:41, Ziyuan Xu wrote:
>>>>
>>>> Control power domain for eMMC via genpd to reduce power consumption.
>>>>
>>>> Signed-off-by: Elaine Zhang <zhangqing@rock-chips.com>
>>>> Signed-off-by: Ziyuan Xu <xzy.xu@rock-chips.com>
>>>>
>>>
>>> It looks nice to me. But this should be merged after applying that[0]
>>> as your patch will break bind/unbind test for sdhci-of-arasan on rk3399
>>> without it[0]. Moreover, Elaine should make sure that upstreamed
>>> rockchip power domain stuff would not off pd for emmc, *otherwise*, I
>>> should update my patch to make sure we update clkmul every time when
>>> doing suspend 2 resume..
>>>
>>>
>> Forgot to say:
>> If use pd, Although there is no call to power odd the pd_emmc,
>> it will be power off when the system doing suspend 2 resume.
>> (Because the system call
>> __device_suspend_noirq->pm_genpd_suspend_noirq->rockchip_pd_power_off)
>
>
> Thanks for explaining this. I checked the code a bit and actually I
> don't need to updata clkmul since it was recorded, although it is still
> reset to 0x10 reading from syscon. So for that, we can now pick it
> up without waiting for my sdhci-of-arasan's update.
>
> Reviewed-by: Shawn Lin <shawn.lin@rock-chips.com>

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.

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'm not sure if this should be done in a generic way where we try to
save and restore all values in the "sdhci_arasan_soc_ctl_map" or if we
should try to be smarter...

-Doug