On Mon, 17 Aug 2020 at 18:49, Sibi Sankar <sibis@xxxxxxxxxxxxxx> wrote: > > On 2020-08-17 14:14, Ulf Hansson wrote: > > On Thu, 13 Aug 2020 at 19:26, Sibi Sankar <sibis@xxxxxxxxxxxxxx> wrote: > >> > >> On 2020-08-13 18:04, Ulf Hansson wrote: > >> > On Wed, 12 Aug 2020 at 19:03, Sibi Sankar <sibis@xxxxxxxxxxxxxx> wrote: > >> >> > >> >> Uffe, > >> >> Thanks for taking time to review the > >> >> series! > >> >> > >> >> On 2020-08-12 15:15, Ulf Hansson wrote: > >> >> > On Tue, 11 Aug 2020 at 21:03, Sibi Sankar <sibis@xxxxxxxxxxxxxx> wrote: > >> >> >> > >> >> >> This is for power domains which needs to stay powered on for suspend > >> >> >> but can be powered on/off as part of runtime PM. This flag is aimed at > >> >> >> power domains coupled to remote processors which enter suspend states > >> >> >> independent to that of the application processor. Such power domains > >> >> >> are turned off only on remote processor crash/shutdown. > >> >> > > >> >> > As Kevin also requested, please elaborate more on the use case. > >> >> > > >> >> > Why exactly must the PM domain stay powered on during system suspend? > >> >> > Is there a wakeup configured that needs to be managed - or is there a > >> >> > co-processor/FW behaviour that needs to be obeyed to? > >> >> > >> >> Yes this is a co-processor behavior that > >> >> needs to be obeyed. Specifically application > >> >> processor notifies the Always on Subsystem > >> >> (AOSS) that a particular co-processor is up > >> >> using the power domains exposed by AOSS QMP > >> >> driver. AOSS uses this information to wait > >> >> for the co-processors to suspend before > >> >> starting its sleep sequence. The application > >> >> processor powers off these power domains only > >> >> if the co-processor has crashed or powered > >> >> off. > >> > > >> > Thanks for clarifying! > >> > > >> > Although, can you please elaborate a bit more on the actual use case? > >> > What are the typical co-processor and what drivers are involved in > >> > managing it? > >> > >> The co-processors using the power domains > >> exposed by qcom_aoss driver are modem, > >> audio dsp, compute dsp managed using > >> qcom_q6v5_mss and qcom_q6v5_pas driver. > >> > >> > > >> > As you may know, runtime PM becomes disabled during system suspend of > >> > a device. Which means, if the driver tries to power off the > >> > coprocessor (via calling pm_runtime_put() for example), somewhere in > >> > the system suspend phase of the corresponding device, its attached PM > >> > domain stays powered on when managed by genpd. > >> > >> The drivers aren't really expected > >> do anything during suspend/resume > >> pretty much because the co-processors > >> enter low-power modes independent to > >> that of the application processor. On > >> co-processor crash the remoteproc core > >> does a pm_stay_awake followed by a > >> pm_relax after crash recovery. > > > > Okay, thanks again for clarifying. You have convinced me about the > > need for a new flag to cope with these use cases. > > > > Would you mind updating the commit message with some of the > > information you just provided? > > > > Additionally, to make it clear that the flag should be used to keep > > the PM domain powered on during system suspend, but only if it's > > already powered on - please rename the flag to GENPD_FLAG_NO_SUSPEND, > > and update the corresponding description of it in the header file. > > Thanks, naming it ^^ makes more sense :) > > https://lore.kernel.org/lkml/340a7aafcf0301ff3158a4e211992041@xxxxxxxxxxxxxx/ > > Also we wouldn't want to power on > runtime suspended power domains with > the NO_SUSPEND flag set, on resume as > explained ^^. Do you agree with that > as well? Actually no. Instead, I think that deserves a separate flag, as it may very well turn out that resuming can be skipped for other cases than "NO_SUSPEND". Therefore, please add a GENPD_FLAG_NO_RESUME for this. Kind regards Uffe
