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

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Date:   Wed, 31 Aug 2016 10:42:40 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Shawn Lin <shawn.lin@...k-chips.com>
Cc:     Elaine Zhang <zhangqing@...k-chips.com>,
        Rob Herring <robh+dt@...nel.org>,
        Heiko Stübner <heiko@...ech.de>,
        Ziyuan Xu <xzy.xu@...k-chips.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Mark Rutland <mark.rutland@....com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Xing Zheng <zhengxing@...k-chips.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Frank Wang <frank.wang@...k-chips.com>,
        Brian Norris <briannorris@...omium.org>,
        Will Deacon <will.deacon@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
        Jianqun Xu <jay.xu@...k-chips.com>,
        David Wu <david.wu@...k-chips.com>,
        Shunqian Zheng <zhengsq@...k-chips.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        Caesar Wang <wxt@...k-chips.com>
Subject: Re: [PATCH 2/2] arm64: dts: rockchip: add eMMC's power domain support
 for rk3399

Hi,

On Sun, Aug 28, 2016 at 8:25 PM, Shawn Lin <shawn.lin@...k-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@...k-chips.com>
>>>> Signed-off-by: Ziyuan Xu <xzy.xu@...k-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@...k-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