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Message-ID: <ZCVyBuKMvDV0gQPW@linaro.org>
Date: Thu, 30 Mar 2023 14:27:02 +0300
From: Abel Vesa <abel.vesa@...aro.org>
To: Saravana Kannan <saravanak@...gle.com>,
Ulf Hansson <ulf.hansson@...aro.org>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>,
Kevin Hilman <khilman@...nel.org>,
Ulf Hansson <ulf.hansson@...aro.org>,
Pavel Machek <pavel@....cz>, Len Brown <len.brown@...el.com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Bjorn Andersson <andersson@...nel.org>,
Andy Gross <agross@...nel.org>,
Konrad Dybcio <konrad.dybcio@...aro.org>,
Mike Turquette <mturquette@...libre.com>,
Stephen Boyd <sboyd@...nel.org>, linux-pm@...r.kernel.org,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
linux-arm-msm@...r.kernel.org, linux-clk@...r.kernel.org,
Doug Anderson <dianders@...omium.org>,
Matthias Kaehlcke <mka@...omium.org>,
Android Kernel Team <kernel-team@...roid.com>
Subject: Re: [PATCH v3 0/4] Allow genpd providers to power off domains on
sync state
On 23-03-27 17:17:28, Saravana Kannan wrote:
> On Mon, Mar 27, 2023 at 12:38 PM Abel Vesa <abel.vesa@...aro.org> wrote:
> >
> > There have been already a couple of tries to make the genpd "disable
> > unused" late initcall skip the powering off of domains that might be
> > needed until later on (i.e. until some consumer probes). The conclusion
> > was that the provider could return -EBUSY from the power_off callback
> > until the provider's sync state has been reached. This patch series tries
> > to provide a proof-of-concept that is working on Qualcomm platforms.
>
> I'm giving my thoughts in the cover letter instead of spreading it
> around all the patches so that there's context between the comments.
>
> 1) Why can't all the logic in this patch series be implemented at the
> framework level? And then allow the drivers to opt into this behavior
> by setting the sync_state() callback.
>
> That way, you can land it only for QC drivers by setting up
> sync_state() callback only for QC drivers, but actually have the same
> code function correctly for non-QC drivers too. And then once we have
> this functionality working properly for QC drivers for one kernel
> version (or two), we'll just have the framework set the device's
> driver's sync_state() if it doesn't have one already.
I think Ulf has already NACK'ed that approach here:
[1] https://lore.kernel.org/lkml/CAPDyKFon35wcQ+5kx3QZb-awN_S_q8y1Sir-G+GoxkCvpN=iiA@mail.gmail.com/
And suggested this new approach that this patch series proposes.
(Unless I missunderstood his point)
>
> 2) sync_state() is not just about power on/off. It's also about the
> power domain level. Can you handle that too please?
Well, this patchset only tries to delay the disabling of unused power
domains until all consumers have had a chance to probe. So we use sync
state only to queue up a power-off request to make sure those unused
ones get disabled.
>
> 3) In your GDSC drivers, it's not clear to me if you are preventing
> power off until sync_state() only for GDSCs that were already on at
> boot. So if an off-at-boot GDSC gets turned on, and then you attempt
> to turn it off before all its consumers have probed, it'll fail to
> power it off even though that wasn't necessary?
I think we can circumvent looking at a GDSC by knowing it there was ever
a power on request since boot. I'll try to come up with something in the
new version.
>
> 4) The returning -EBUSY when a power off is attempted seems to be
> quite wasteful. The framework will go through the whole sequence of
> trying to power down, send the notifications and then fail and then
> send the undo notifications. Combined with point (2) I think this can
> be handled better at the aggregation level in the framework to avoid
> even going that far into the power off sequence.
Again, have a look at [1] (above).
Ulf, any thoughts on this 4th point?
>
> -Saravana
>
> >
> > I've been doing extensive testing on SM8450, but I've also spinned this
> > on my X13s (SC8280XP). Both patches that add the sync state callback to
> > the SC8280XP and SM8450 are here to provide context. Once we agree on
> > the form, I intend to add the sync state callback to all gdsc providers.
> >
> > Currently, some of the gdsc providers might not reach sync state due to
> > list of consumers not probing yet (or at all). The sync state can be
> > enforced by writing 1 to the state_synced sysfs attribute of the
> > provider, thanks to Saravana's commit [1] which has been already merged.
> >
> > [1] https://lore.kernel.org/r/20230304005355.746421-3-saravanak@google.com
> >
> > V2 (RFC) of this patchset was here:
> > https://lore.kernel.org/all/20230320134217.1685781-1-abel.vesa@linaro.org/
> >
> > Changes since v2:
> > * renamed genpd_queue_power_off_work to pm_genpd_queue_power_off and added
> > comment about its purpose w.r.t. it being exported.
> > * added the qcom_cc generic sync state callback to all providers that
> > register GDSCs, instead of SM8450 and SC8280XP
> >
> > Changes since v1:
> > * Added the qcom_cc sync state callback which calls in turn the gdsc one
> > * dropped extra semicolon from pm_domain.h
> >
> > Abel Vesa (4):
> > PM: domains: Allow power off queuing from providers
> > soc: qcom: rpmhpd: Do proper power off when state synced
> > clk: qcom: gdsc: Avoid actual power off until sync state
> > clk: qcom: Add sync state callback to all providers
> >
> > drivers/base/power/domain.c | 18 ++++++++++--------
> > drivers/clk/qcom/apss-ipq6018.c | 1 +
> > drivers/clk/qcom/camcc-sc7180.c | 1 +
> > drivers/clk/qcom/camcc-sc7280.c | 1 +
> > drivers/clk/qcom/camcc-sdm845.c | 1 +
> > drivers/clk/qcom/camcc-sm6350.c | 1 +
> > drivers/clk/qcom/camcc-sm8250.c | 1 +
> > drivers/clk/qcom/camcc-sm8450.c | 1 +
> > drivers/clk/qcom/common.c | 19 +++++++++++++++++++
> > drivers/clk/qcom/common.h | 2 ++
> > drivers/clk/qcom/dispcc-qcm2290.c | 1 +
> > drivers/clk/qcom/dispcc-sc7180.c | 1 +
> > drivers/clk/qcom/dispcc-sc7280.c | 1 +
> > drivers/clk/qcom/dispcc-sc8280xp.c | 1 +
> > drivers/clk/qcom/dispcc-sdm845.c | 1 +
> > drivers/clk/qcom/dispcc-sm6115.c | 1 +
> > drivers/clk/qcom/dispcc-sm6125.c | 1 +
> > drivers/clk/qcom/dispcc-sm6350.c | 1 +
> > drivers/clk/qcom/dispcc-sm6375.c | 1 +
> > drivers/clk/qcom/dispcc-sm8250.c | 1 +
> > drivers/clk/qcom/dispcc-sm8450.c | 1 +
> > drivers/clk/qcom/dispcc-sm8550.c | 1 +
> > drivers/clk/qcom/gcc-apq8084.c | 1 +
> > drivers/clk/qcom/gcc-ipq806x.c | 1 +
> > drivers/clk/qcom/gcc-ipq8074.c | 1 +
> > drivers/clk/qcom/gcc-mdm9615.c | 1 +
> > drivers/clk/qcom/gcc-msm8660.c | 1 +
> > drivers/clk/qcom/gcc-msm8909.c | 1 +
> > drivers/clk/qcom/gcc-msm8916.c | 1 +
> > drivers/clk/qcom/gcc-msm8939.c | 1 +
> > drivers/clk/qcom/gcc-msm8953.c | 1 +
> > drivers/clk/qcom/gcc-msm8960.c | 1 +
> > drivers/clk/qcom/gcc-msm8974.c | 1 +
> > drivers/clk/qcom/gcc-msm8976.c | 1 +
> > drivers/clk/qcom/gcc-msm8994.c | 1 +
> > drivers/clk/qcom/gcc-msm8996.c | 1 +
> > drivers/clk/qcom/gcc-msm8998.c | 1 +
> > drivers/clk/qcom/gcc-qcm2290.c | 1 +
> > drivers/clk/qcom/gcc-qcs404.c | 1 +
> > drivers/clk/qcom/gcc-qdu1000.c | 1 +
> > drivers/clk/qcom/gcc-sa8775p.c | 1 +
> > drivers/clk/qcom/gcc-sc7180.c | 1 +
> > drivers/clk/qcom/gcc-sc7280.c | 1 +
> > drivers/clk/qcom/gcc-sc8180x.c | 1 +
> > drivers/clk/qcom/gcc-sc8280xp.c | 1 +
> > drivers/clk/qcom/gcc-sdm660.c | 1 +
> > drivers/clk/qcom/gcc-sdm845.c | 1 +
> > drivers/clk/qcom/gcc-sdx55.c | 1 +
> > drivers/clk/qcom/gcc-sdx65.c | 1 +
> > drivers/clk/qcom/gcc-sm6115.c | 1 +
> > drivers/clk/qcom/gcc-sm6125.c | 1 +
> > drivers/clk/qcom/gcc-sm6350.c | 1 +
> > drivers/clk/qcom/gcc-sm6375.c | 1 +
> > drivers/clk/qcom/gcc-sm7150.c | 1 +
> > drivers/clk/qcom/gcc-sm8150.c | 1 +
> > drivers/clk/qcom/gcc-sm8250.c | 1 +
> > drivers/clk/qcom/gcc-sm8350.c | 1 +
> > drivers/clk/qcom/gcc-sm8450.c | 1 +
> > drivers/clk/qcom/gcc-sm8550.c | 1 +
> > drivers/clk/qcom/gdsc.c | 26 ++++++++++++++++++++++++++
> > drivers/clk/qcom/gdsc.h | 6 ++++++
> > drivers/clk/qcom/gpucc-msm8998.c | 1 +
> > drivers/clk/qcom/gpucc-sc7180.c | 1 +
> > drivers/clk/qcom/gpucc-sc7280.c | 1 +
> > drivers/clk/qcom/gpucc-sc8280xp.c | 1 +
> > drivers/clk/qcom/gpucc-sdm660.c | 1 +
> > drivers/clk/qcom/gpucc-sdm845.c | 1 +
> > drivers/clk/qcom/gpucc-sm6115.c | 1 +
> > drivers/clk/qcom/gpucc-sm6125.c | 1 +
> > drivers/clk/qcom/gpucc-sm6350.c | 1 +
> > drivers/clk/qcom/gpucc-sm6375.c | 1 +
> > drivers/clk/qcom/gpucc-sm8150.c | 1 +
> > drivers/clk/qcom/gpucc-sm8250.c | 1 +
> > drivers/clk/qcom/gpucc-sm8350.c | 1 +
> > drivers/clk/qcom/lcc-ipq806x.c | 1 +
> > drivers/clk/qcom/lpassaudiocc-sc7280.c | 1 +
> > drivers/clk/qcom/lpasscc-sc7280.c | 1 +
> > drivers/clk/qcom/lpasscorecc-sc7180.c | 2 ++
> > drivers/clk/qcom/lpasscorecc-sc7280.c | 2 ++
> > drivers/clk/qcom/mmcc-apq8084.c | 1 +
> > drivers/clk/qcom/mmcc-msm8974.c | 1 +
> > drivers/clk/qcom/mmcc-msm8994.c | 1 +
> > drivers/clk/qcom/mmcc-msm8996.c | 1 +
> > drivers/clk/qcom/mmcc-msm8998.c | 1 +
> > drivers/clk/qcom/mmcc-sdm660.c | 1 +
> > drivers/clk/qcom/videocc-sc7180.c | 1 +
> > drivers/clk/qcom/videocc-sc7280.c | 1 +
> > drivers/clk/qcom/videocc-sdm845.c | 1 +
> > drivers/clk/qcom/videocc-sm8150.c | 1 +
> > drivers/clk/qcom/videocc-sm8250.c | 1 +
> > drivers/soc/qcom/rpmhpd.c | 19 +++++++------------
> > include/linux/pm_domain.h | 4 ++++
> > 92 files changed, 161 insertions(+), 20 deletions(-)
> >
> > --
> > 2.34.1
> >
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