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

[Alan Stern <stern@rowland.harvard.edu>]

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
> [   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.

Alan Stern