linux-kernel - Re: [PATCH 0/5] Add power domain support for dw

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Date:	Mon, 1 Aug 2016 11:10:57 +0800
From:	Shawn Lin <shawn.lin@...k-chips.com>
To:	Ulf Hansson <ulf.hansson@...aro.org>
Cc:	shawn.lin@...k-chips.com, Heiko Stuebner <heiko@...ech.de>,
	Rob Herring <robh+dt@...nel.org>,
	Jaehoon Chung <jh80.chung@...sung.com>,
	linux-mmc <linux-mmc@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
	Douglas Anderson <dianders@...omium.org>,
	Brian Norris <briannorris@...omium.org>,
	Feng Xiao <xf@...k-chips.com>,
	Elaine Zhang <zhangqing@...k-chips.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/5] Add power domain support for dw_mmc/sdhci-of-arasan

在 2016/7/29 17:21, Ulf Hansson 写道:
> On 29 July 2016 at 06:14, Shawn Lin <shawn.lin@...k-chips.com> wrote:
>>
>> We need to enable the power domain manually while probing as the
>> power policy will turn off the pd which is not referenced. Otherwise
>
> I assume you are going to use the generic PM domain (genpd)?

yes.

> If so, this statement isn't entirely correct.
>
> As a matter of fact, the PM domain will be "powered on" once you have
> registered your PM domain with genpd and when the device (dw_mmc etc)
> gets attached to the domain. The attach occurs when the platform bus'
> ->probe() function get invoked for the device.
>
> Genpd monitors each device within the domain. To allow it to "power
> off", all devices in same domain needs to be runtime PM enabled and
> runtime PM suspended.

I will check this with my PM guys as I have limited knowledge about
PM stuff. Thanks for these great info.


So, if my real intention is to just enable genpd to make sure it will
be in "power on " stat, I just need to update my DTS/DTB. That would be
great.:)

>
> Due to this, you should be able to deploy genpd support+an updated
> DTB, without first having to deploying runtime PM support in the
> related drivers. In other words, you should be able to work on these
> things almost independently of each other.

sure.

>
>> we may take risk of breaking kernel once Feng Xiao land the rockchip pd
>> relate stuff. So, let's do it in advance.
>>
>> This pachset is based on the latest linux-next[1] which should contain
>> the next branch of linux-mmc and dt stuff. It's ideal to pack these all
>> into Ulf' tree with Heiko's ack for dts, Rob's ack for Doc and Jaehoon's
>> ack for dw_mmc. But it's okay to be merged seperately.
>>
>> [1] git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
>>
>> Thanks.
>>
>>
>>
>> Shawn Lin (5):
>>   Documentation: mmc: synopsys-dw-mshc: add power domain description
>>   Documentation: mmc: sdhci-of-arasan: add power domain description
>
> To me this isn't necessary to describe for each device. I think
> Documentation/devicetree/bindings/power/power_domain.txt describes all
> that is needed.
>
>>   arm64: dts: rockchip: Provide power-domains for sd/sdio/emmc
>>     controllers
>>   mmc: dw_mmc: add power domain support
>>   mmc: sdhci-of-arasan: add power domain support
>
> I would rephrase these commit message headers, to something like
> "Deploy runtime PM support", as that is actually what you intend to
> do.
>
>>
>>  Documentation/devicetree/bindings/mmc/arasan,sdhci.txt     |  1 +
>>  Documentation/devicetree/bindings/mmc/synopsys-dw-mshc.txt |  2 ++
>>  arch/arm64/boot/dts/rockchip/rk3399.dtsi                   |  3 +++
>>  drivers/mmc/host/dw_mmc.c                                  | 11 +++++++++++
>>  drivers/mmc/host/sdhci-of-arasan.c                         | 10 ++++++++++
>>  5 files changed, 27 insertions(+)
>>
>> --
>> 2.3.7
>>
>>
>
> Kind regards
> Uffe
>
>
>


-- 
Best Regards
Shawn Lin