linux-kernel - Re: [RESEND PATCH v16 4/4] ARM: dts: add the support power-domain node on RK3288 SoCs

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Date:	Thu, 27 Aug 2015 17:24:13 -0700
From:	Kevin Hilman <khilman@...nel.org>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:	Doug Anderson <dianders@...omium.org>,
	Caesar Wang <wxt@...k-chips.com>,
	Heiko Stübner <heiko@...ech.de>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	"linux-arm-kernel\@lists.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"open list\:ARM\/Rockchip SoC..." 
	<linux-rockchip@...ts.infradead.org>,
	Tomasz Figa <tomasz.figa@...il.com>,
	"linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>,
	Kumar Gala <galak@...eaurora.org>,
	Russell King <linux@....linux.org.uk>,
	Rob Herring <robh+dt@...nel.org>,
	Arnd Bergmann <arnd@...db.de>,
	Linus Walleij <linus.walleij@...aro.org>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	"devicetree\@vger.kernel.org" <devicetree@...r.kernel.org>,
	"jinkun.hong" <jinkun.hong@...k-chips.com>
Subject: Re: [RESEND PATCH v16 4/4] ARM: dts: add the support power-domain node on RK3288 SoCs

Dmitry Torokhov <dmitry.torokhov@...il.com> writes:

> On Tue, Aug 25, 2015 at 3:45 PM, Kevin Hilman <khilman@...nel.org> wrote:
>> Doug Anderson <dianders@...omium.org> writes:
>>
>>> To put things in a
>>> concrete way, for pd_vio we'd go through the entire device tree
>>> ourselves and find all properties that look like "power-domains =
>>> <&power RK3288_PD_VIO>;".  We'd then find the parent of those
>>> properties and look for a property named "clocks".  We'd then iterate
>>> over all those clocks and turn those on.  Did I get that right?
>>
>> ... but you make it sound like more work than it is.  The genpd already
>> keeps a list of devices that refer to the power domain.  In fact, the
>> genpd 'attach' method can be platform-specific, so could be used to keep
>> track of a list (or a subset) of clocks which are needed for reset.
>
> That is not really workable: the attach and detach happen in
> probe/remove path; if you do not have driver for the device you will
> miss the clocks for it. 

And in my proposal, I suggested that clocks without drivers are
good candidates to list in the domain, with the caveat that the be
called out (documented) as being device clocks that are missing a
driver, so when a driver shows up they can be moved accordingly, and in
a way that actually describes the hardware.

> And the quirk of this SoC is that we need to
> turn all clocks during domain transition, regardless of whether there
> is a driver for all devices.

I understand.  And that "quirk" is not unique to rockchip socs.

Kevin




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