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Wysocki" , Rob Herring , Krzysztof Kozlowski , Conor Dooley , linux-pm@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH v2 2/3] cpufreq: qcom-nvmem: Enable virtual power domain devices Message-ID: References: <20231018-msm8909-cpufreq-v2-0-0962df95f654@kernkonzept.com> <20231018-msm8909-cpufreq-v2-2-0962df95f654@kernkonzept.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-0.8 required=5.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on morse.vger.email Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (morse.vger.email [0.0.0.0]); Tue, 24 Oct 2023 09:25:52 -0700 (PDT) On Tue, Oct 24, 2023 at 06:11:34PM +0200, Ulf Hansson wrote: > On Tue, 24 Oct 2023 at 15:07, Stephan Gerhold > wrote: > > > > On Tue, Oct 24, 2023 at 02:49:32PM +0200, Ulf Hansson wrote: > > > On Tue, 24 Oct 2023 at 14:03, Stephan Gerhold > > > wrote: > > > > > > > > On Thu, Oct 19, 2023 at 01:26:19PM +0200, Ulf Hansson wrote: > > > > > On Thu, 19 Oct 2023 at 12:24, Ulf Hansson wrote: > > > > > > > > > > > > On Wed, 18 Oct 2023 at 10:06, Stephan Gerhold > > > > > > wrote: > > > > > > > > > > > > > > The genpd core caches performance state votes from devices that are > > > > > > > runtime suspended as of commit 3c5a272202c2 ("PM: domains: Improve > > > > > > > runtime PM performance state handling"). They get applied once the > > > > > > > device becomes active again. > > > > > > > > > > > > > > To attach the power domains needed by qcom-cpufreq-nvmem the OPP core > > > > > > > calls genpd_dev_pm_attach_by_id(). This results in "virtual" dummy > > > > > > > devices that use runtime PM only to control the enable and performance > > > > > > > state for the attached power domain. > > > > > > > > > > > > > > However, at the moment nothing ever resumes the virtual devices created > > > > > > > for qcom-cpufreq-nvmem. They remain permanently runtime suspended. This > > > > > > > means that performance state votes made during cpufreq scaling get > > > > > > > always cached and never applied to the hardware. > > > > > > > > > > > > > > Fix this by enabling the devices after attaching them and use > > > > > > > dev_pm_syscore_device() to ensure the power domains also stay on when > > > > > > > going to suspend. Since it supplies the CPU we can never turn it off > > > > > > > from Linux. There are other mechanisms to turn it off when needed, > > > > > > > usually in the RPM firmware (RPMPD) or the cpuidle path (CPR genpd). > > > > > > > > > > > > I believe we discussed using dev_pm_syscore_device() for the previous > > > > > > version. It's not intended to be used for things like the above. > > > > > > > > > > > > Moreover, I was under the impression that it wasn't really needed. In > > > > > > fact, I would think that this actually breaks things for system > > > > > > suspend/resume, as in this case the cpr driver's genpd > > > > > > ->power_on|off() callbacks are no longer getting called due this, > > > > > > which means that the cpr state machine isn't going to be restored > > > > > > properly. Or did I get this wrong? > > > > > > > > > > BTW, if you really need something like the above, the proper way to do > > > > > it would instead be to call device_set_awake_path() for the device. > > > > > > > > > > > > > Unfortunately this does not work correctly. When I use > > > > device_set_awake_path() it does set dev->power.wakeup_path = true. > > > > However, this flag is cleared again in device_prepare() when entering > > > > suspend. To me it looks a bit like wakeup_path is not supposed to be set > > > > directly by drivers? Before and after your commit 8512220c5782 ("PM / > > > > core: Assign the wakeup_path status flag in __device_prepare()") it > > > > seems to be internally bound to device_may_wakeup(). > > > > > > > > It works if I make device_may_wakeup() return true, with > > > > > > > > device_set_wakeup_capable(dev, true); > > > > device_wakeup_enable(dev); > > > > > > > > but that also allows *disabling* the wakeup from sysfs which doesn't > > > > really make sense for the CPU. > > > > > > > > Any ideas? > > > > > > The device_set_awake_path() should be called from a system suspend > > > callback. So you need to add that callback for the cpufreq driver. > > > > > > Sorry, if that wasn't clear. > > > > > > > Hmm, but at the moment I'm calling this on the virtual genpd devices. > > How would it work for them? I don't have a suspend callback for them. > > > > I guess could loop over the virtual devices in the cpufreq driver > > suspend callback, but is my driver suspend callback really guaranteed to > > run before the device_prepare() that clears "wakeup_path" on the virtual > > devices? > > Yes, that's guaranteed. dpm_prepare() (which calls device_prepare()) > is always being executed before dpm_suspend(). > Thanks, I think I understand. Maybe. :-) Just to confirm, I should call device_set_awake_path() for the virtual genpd devices as part of the PM ->suspend() callback? And this will be guaranteed to run after the "prepare" phase but before the "suspend_noirq" phase where the genpd core will check the wakeup flag? Thanks, Stepan