On Tue, 24 Oct 2023 at 14:03, Stephan Gerhold stephan.gerhold@kernkonzept.com wrote:
On Thu, Oct 19, 2023 at 01:26:19PM +0200, Ulf Hansson wrote:
On Thu, 19 Oct 2023 at 12:24, Ulf Hansson ulf.hansson@linaro.org wrote:
On Wed, 18 Oct 2023 at 10:06, Stephan Gerhold stephan.gerhold@kernkonzept.com 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.
Kind regards Uffe