From: Ulf Hansson <ulf.hansson@linaro.org>
To: Sudeep Holla <sudeep.holla@arm.com>
Cc: Lina Iyer <ilina@codeaurora.org>,
Maulik Shah <mkshah@codeaurora.org>,
Stephen Boyd <swboyd@chromium.org>,
Andy Gross <agross@kernel.org>,
David Brown <david.brown@linaro.org>,
Lorenzo Pieralisi <Lorenzo.Pieralisi@arm.com>,
linux-arm-msm <linux-arm-msm@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Linux PM <linux-pm@vger.kernel.org>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
Bjorn Andersson <bjorn.andersson@linaro.org>,
Evan Green <evgreen@chromium.org>,
Doug Anderson <dianders@chromium.org>,
Rajendra Nayak <rnayak@codeaurora.org>,
lsrao@codeaurora.org, "Rafael J. Wysocki" <rjw@rjwysocki.net>
Subject: Re: [PATCH v3 5/7] drivers: firmware: psci: Add hierarchical domain idle states converter
Date: Fri, 7 Feb 2020 13:32:28 +0100 [thread overview]
Message-ID: <CAPDyKFp-zvD1iFcpRaTFiuazxYmLEx0Czf3=TZJxjSCDmmPsvA@mail.gmail.com> (raw)
In-Reply-To: <20200207111955.GA40103@bogus>
[...]
> > I understand the arguments for using PC vs OSI and agree with it. But
> > what in PSCI is against Linux knowing when the last core is powering
> > down when the PSCI is configured to do only Platform Cordinated.
>
> Nothing :D. But knowing the evolution and reasons for adding OSI in the
> PSCI specification and having argued about benefits of OSI over PC for
> years and finally when we have it in mainline, this argument of using
> PC for exact reasons why OSI evolved is something I can't understand
> and I am confused.
>
> > There should not be any objection to drivers knowing when all the cores
> > are powered down, be it reference counting CPU PM notifications or using
> > a cleaner approach like this where GendPD framwork does everything
> > cleanly and gives a nice callback. ARM architecture allows for different
> > aspects of CPU access be handled at different levels. I see this as an
> > extension of that approach.
> >
>
> One thing that was repeatedly pointed out during OSI patch review was no
> extra overhead for PC mode where firmware can make decisions. So, just
> use OSI now and let us be done with this discussion of OSI vs PC. If PC
> is what you think you need for future, we can revert all OSI changes and
> start discussing again :-)
Just to make it clear, I fully agree with you in regards to overhead
for PC-mode. This is especially critical for ARM SoCs with lots of
cores, I assume.
However, the overhead you refer to, is *only* going to be present in
case when the DTS has the hierarchical CPU topology description with
"power-domains". Because, that is *optional* to use, I am expecting
only those SoC/platforms that needs to manage last-man activities to
use this layout, the others will remain unaffected.
That said, does that address your concern?
Kind regards
Uffe
next prev parent reply other threads:[~2020-02-07 12:33 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-03 13:35 [PATCH v3 0/7] Add RSC power domain support Maulik Shah
2020-02-03 13:35 ` [PATCH v3 1/7] drivers: qcom: rpmh: fix macro to accept NULL argument Maulik Shah
2020-02-03 13:35 ` [PATCH v3 2/7] drivers: qcom: rpmh: remove rpmh_flush export Maulik Shah
2020-02-03 13:35 ` [PATCH v3 3/7] dt-bindings: soc: qcom: Add RSC power domain specifier Maulik Shah
2020-02-03 13:35 ` [PATCH v3 4/7] drivers: qcom: rpmh-rsc: Add RSC power domain support Maulik Shah
2020-02-03 13:35 ` [PATCH v3 5/7] drivers: firmware: psci: Add hierarchical domain idle states converter Maulik Shah
2020-02-03 17:08 ` Sudeep Holla
2020-02-04 4:52 ` Maulik Shah
2020-02-04 15:21 ` Sudeep Holla
2020-02-05 12:23 ` Maulik Shah
2020-02-05 14:06 ` Sudeep Holla
2020-02-05 15:55 ` Ulf Hansson
2020-02-05 16:18 ` Sudeep Holla
2020-02-06 8:45 ` Ulf Hansson
2020-02-06 20:45 ` Lina Iyer
2020-02-07 11:20 ` Sudeep Holla
2020-02-07 12:32 ` Ulf Hansson [this message]
2020-02-07 14:48 ` Lorenzo Pieralisi
2020-02-07 15:52 ` Ulf Hansson
2020-02-07 16:15 ` Sudeep Holla
2020-02-08 10:25 ` Ulf Hansson
2020-02-10 10:31 ` Sudeep Holla
2020-02-07 16:05 ` Sudeep Holla
2020-02-06 21:11 ` Bjorn Andersson
2020-02-07 11:25 ` Sudeep Holla
2020-02-03 13:35 ` [PATCH v3 6/7] arm64: dts: qcom: sc7180: Add cpuidle low power states Maulik Shah
2020-02-04 23:15 ` Matthias Kaehlcke
2020-02-05 12:07 ` Maulik Shah
2020-02-03 13:35 ` [PATCH v3 7/7] arm64: dts: qcom: sc7180: Convert to the hierarchical CPU topology layout Maulik Shah
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