Re: [PATCH v6 0/6] clk: qcom: use power-domain for sm8250's clock controllers

From: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
To: Stephen Boyd <sboyd@kernel.org>
Cc: Andy Gross <agross@kernel.org>,
	Bjorn Andersson <bjorn.andersson@linaro.org>,
	Jonathan Marek <jonathan@marek.ca>,
	Michael Turquette <mturquette@baylibre.com>,
	Rob Herring <robh+dt@kernel.org>,
	Taniya Das <tdas@codeaurora.org>,
	"open list:DRM DRIVER FOR MSM ADRENO GPU" 
	<linux-arm-msm@vger.kernel.org>,
	"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
	<devicetree@vger.kernel.org>,
	"open list:COMMON CLK FRAMEWORK" <linux-clk@vger.kernel.org>,
	"Bryan O'Donoghue" <bryan.odonoghue@linaro.org>,
	Mark Brown <broonie@kernel.org>,
	Ulf Hansson <ulf.hansson@linaro.org>,
	open list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v6 0/6] clk: qcom: use power-domain for sm8250's clock controllers
Date: Sun, 29 Aug 2021 18:54:02 +0300	[thread overview]
Message-ID: <CAA8EJppo8Zze5ViYOWooHy=RR4ueXNeWiBFyKdtpUcm5Cs69ew@mail.gmail.com> (raw)
In-Reply-To: <163020909027.2218116.11109424225803296345@swboyd.mtv.corp.google.com>

On Sun, 29 Aug 2021 at 06:51, Stephen Boyd <sboyd@kernel.org> wrote:
>
> Quoting Dmitry Baryshkov (2021-08-26 14:56:23)
> > On 26/08/2021 21:31, Stephen Boyd wrote:
> > > Quoting Dmitry Baryshkov (2021-07-27 13:19:56)
> > >> On SM8250 both the display and video clock controllers are powered up by
> > >> the MMCX power domain. Handle this by linking clock controllers to the
> > >> proper power domain, and using runtime power management to enable and
> > >> disable the MMCX power domain.
> > >>
> > >> Dependencies:
> > >> - https://lore.kernel.org/linux-arm-msm/20210703005416.2668319-1-bjorn.andersson@linaro.org/
> > >>    (pending)
> > >
> > > Does this patch series need to go through the qcom tree? Presumably the
> > > dependency is going through qcom -> arm-soc
> >
> > It looks like Bjorn did not apply his patches in the for-5.15 series, so
> > we'd have to wait anyway. Probably I should rebase these patches instead
> > on Rajendra's required-opps patch (which is going in this window).
> >
>
> Ok. Thanks. I'll drop it from my queue for now.

Just for the reference. I've sent v7 of this patchset. After thinking
more about power domains relationship, I think we have a hole in the
abstraction here. Currently subdomains cause power domains to be
powered up, but do not dictate the performance level the parent domain
should be working in. While this does not look like an issue for the
gdsc (and thus it can be easily solved by the Bjorn's patches, which
enforce rpmhpd to be powered on to 'at least lowest possible'
performance state, this might be not the case for the future links. I
think at some point the pd_add_subdomain() interface should be
extended with the ability to specify minimum required performance
state when the link becomes on. Until that time I have changed code to
enforce having clock controller in pm resume state when gdsc is
enabled, thus CC itself votes on parent's (rpmhpd) performance state.

-- 
With best wishes
Dmitry