Re: [PATCH v10 1/2] scsi: ufs: Enable power management for wlun

["Rafael J. Wysocki" <rafael@kernel.org>]

On Sat, Mar 6, 2021 at 5:17 PM Alan Stern <stern@rowland.harvard.edu> wrote:
>
> On Fri, Mar 05, 2021 at 06:54:24PM -0800, Asutosh Das (asd) wrote:
>
> > Now during my testing I see a weird issue sometimes (1 in 7).
> > Scenario - bootups
> >
> > Issue:
> > The supplier 'ufs_device_wlun 0:0:0:49488' goes into runtime suspend even
> > when one/more of its consumers are in RPM_ACTIVE state.
> >
> > *Log:
> > [   10.056379][  T206] sd 0:0:0:1: [sdb] Synchronizing SCSI cache
> > [   10.062497][  T113] sd 0:0:0:5: [sdf] Synchronizing SCSI cache
> > [   10.356600][   T32] sd 0:0:0:7: [sdh] Synchronizing SCSI cache
> > [   10.362944][  T174] sd 0:0:0:3: [sdd] Synchronizing SCSI cache
> > [   10.696627][   T83] sd 0:0:0:2: [sdc] Synchronizing SCSI cache
> > [   10.704562][  T170] sd 0:0:0:6: [sdg] Synchronizing SCSI cache
> > [   10.980602][    T5] sd 0:0:0:0: [sda] Synchronizing SCSI cache
> >
> > /** Printing all the consumer nodes of supplier **/
> > [   10.987327][    T5] ufs_device_wlun 0:0:0:49488: usage-count @ suspend: 0
> > <-- this is the usage_count
> > [   10.994440][    T5] ufs_rpmb_wlun 0:0:0:49476: PM state - 2
> > [   11.000402][    T5] scsi 0:0:0:49456: PM state - 2
> > [   11.005453][    T5] sd 0:0:0:0: PM state - 2
> > [   11.009958][    T5] sd 0:0:0:1: PM state - 2
> > [   11.014469][    T5] sd 0:0:0:2: PM state - 2
> > [   11.019072][    T5] sd 0:0:0:3: PM state - 2
> > [   11.023595][    T5] sd 0:0:0:4: PM state - 0 << RPM_ACTIVE
> > [   11.353298][    T5] sd 0:0:0:5: PM state - 2
> > [   11.357726][    T5] sd 0:0:0:6: PM state - 2
> > [   11.362155][    T5] sd 0:0:0:7: PM state - 2
> > [   11.366584][    T5] ufshcd-qcom 1d84000.ufshc: __ufshcd_wl_suspend - 8709
> > [   11.374366][    T5] ufs_device_wlun 0:0:0:49488: __ufshcd_wl_suspend -
> > (0) has rpm_active flags

Do you mean that rpm_active of the link between the consumer and the
supplier is greater than 0 at this point and the consumer is
RPM_ACTIVE, but the supplier suspends successfully nevertheless?

> > [   11.383376][    T5] ufs_device_wlun 0:0:0:49488:
> > ufshcd_wl_runtime_suspend <-- Supplier suspends fine.
> > [   12.977318][  T174] sd 0:0:0:4: [sde] Synchronizing SCSI cache
> >
> > And the the suspend of sde is stuck now:
> > schedule+0x9c/0xe0
> > schedule_timeout+0x40/0x128
> > io_schedule_timeout+0x44/0x68
> > wait_for_common_io+0x7c/0x100
> > wait_for_completion_io+0x14/0x20
> > blk_execute_rq+0x90/0xcc
> > __scsi_execute+0x104/0x1c4
> > sd_sync_cache+0xf8/0x2a0
> > sd_suspend_common+0x74/0x11c
> > sd_suspend_runtime+0x14/0x20
> > scsi_runtime_suspend+0x64/0x94
> > __rpm_callback+0x80/0x2a4
> > rpm_suspend+0x308/0x614
> > pm_runtime_work+0x98/0xa8
> >
> > I added 'DL_FLAG_RPM_ACTIVE' while creating links.
> >       if (hba->sdev_ufs_device) {
> >               link = device_link_add(&sdev->sdev_gendev,
> >                                   &hba->sdev_ufs_device->sdev_gendev,
> >                                  DL_FLAG_PM_RUNTIME|DL_FLAG_RPM_ACTIVE);
> > I didn't expect this to resolve the issue anyway and it didn't.
> >
> > Another interesting point here is when I resume any of the above suspended
> > consumers, it all goes back to normal, which is kind of expected. I tried
> > resuming the consumer and the supplier is resumed and the supplier is
> > suspended when all the consumers are suspended.
> >
> > Any pointers on this issue please?
> >
> > @Bart/@Alan - Do you've any pointers please?
>
> It's very noticeable that although you seem to have isolated a bug in
> the power management subsystem (supplier goes into runtime suspend
> even when one of its consumers is still active), you did not CC the
> power management maintainer or mailing list.
>
> I have added the appropriate CC's.

Thanks Alan!