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

[Asutosh Das (asd)]

On 3/8/2021 9:17 AM, Rafael J. Wysocki wrote:
> On Mon, Mar 8, 2021 at 5:21 PM Rafael J. Wysocki <rafael at kernel.org> wrote:
>>
>> On Sat, Mar 6, 2021 at 5:17 PM Alan Stern <stern at 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
> 
> I mean is rpm_active of the link greater than 1 (because 1 means "no
> active references to the supplier")?
Hi Rafael:
No - it is not greater than 1.

I'm trying to understand what's going on in it; will update when I've 
something.

> 
>> 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!


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