Re: [PATCH v14 1/2] scsi: ufs: Enable power management for wlun

[Adrian Hunter <adrian.hunter@intel.com>]

On 1/04/21 4:40 am, Asutosh Das (asd) wrote:
> On 3/31/2021 11:19 AM, Adrian Hunter wrote:
>> On 31/03/21 1:31 am, Asutosh Das wrote:
>>> During runtime-suspend of ufs host, the scsi devices are
>>> already suspended and so are the queues associated with them.
>>> But the ufs host sends SSU (START_STOP_UNIT) to wlun
>>> during its runtime-suspend.
>>> During the process blk_queue_enter checks if the queue is not in
>>> suspended state. If so, it waits for the queue to resume, and never
>>> comes out of it.
>>> The commit
>>> (d55d15a33: scsi: block: Do not accept any requests while suspended)
>>> adds the check if the queue is in suspended state in blk_queue_enter().
>>>
>>> Call trace:
>>>   __switch_to+0x174/0x2c4
>>>   __schedule+0x478/0x764
>>>   schedule+0x9c/0xe0
>>>   blk_queue_enter+0x158/0x228
>>>   blk_mq_alloc_request+0x40/0xa4
>>>   blk_get_request+0x2c/0x70
>>>   __scsi_execute+0x60/0x1c4
>>>   ufshcd_set_dev_pwr_mode+0x124/0x1e4
>>>   ufshcd_suspend+0x208/0x83c
>>>   ufshcd_runtime_suspend+0x40/0x154
>>>   ufshcd_pltfrm_runtime_suspend+0x14/0x20
>>>   pm_generic_runtime_suspend+0x28/0x3c
>>>   __rpm_callback+0x80/0x2a4
>>>   rpm_suspend+0x308/0x614
>>>   rpm_idle+0x158/0x228
>>>   pm_runtime_work+0x84/0xac
>>>   process_one_work+0x1f0/0x470
>>>   worker_thread+0x26c/0x4c8
>>>   kthread+0x13c/0x320
>>>   ret_from_fork+0x10/0x18
>>>
>>> Fix this by registering ufs device wlun as a scsi driver and
>>> registering it for block runtime-pm. Also make this as a
>>> supplier for all other luns. That way, this device wlun
>>> suspends after all the consumers and resumes after
>>> hba resumes.
>>>
>>> Co-developed-by: Can Guo <cang@codeaurora.org>
>>> Signed-off-by: Can Guo <cang@codeaurora.org>
>>> Signed-off-by: Asutosh Das <asutoshd@codeaurora.org>
>>> ---
>>
> Hi Adrian
> Thanks for the comments.
>> Looks good but still doesn't seem to based on the latest tree.
>>
> Umm, it's based on the below:
> git://git.kernel.org/pub/scm/linux/kernel/git/mkp/scsi.git
> Branch: refs/heads/for-next
> 
> The top most change is e27f3c8 on 27th March'21.
> Which tree are you referring to that'd be latest?

Dunno, but that seems to be missing:

  commit aa53f580e67b49ec5f4d9bd1de81eb9eb0dc079f
  Author: Can Guo <cang@codeaurora.org>
  Date:   Tue Feb 23 21:36:47 2021 -0800

    scsi: ufs: Minor adjustments to error handling

which is in v5.12-rc3

> 
>> Also came across the issue below:
>>
>> <SNIP>
>>
>>> +#ifdef CONFIG_PM_SLEEP
>>> +static int ufshcd_wl_poweroff(struct device *dev)
>>> +{
>>> +    ufshcd_wl_shutdown(dev);
>>
>> This turned out to be wrong.  This is a PM op and SCSI has already
>> quiesced the sdev's.  All that is needed isOk. I'll fix it in the next version.
> 
>>
>>     __ufshcd_wl_suspend(hba, UFS_SHUTDOWN_PM);
>>
>>> +    return 0;
>>> +}
>>> +#endif
> 
>