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Subject: Re: [PATCH v18 1/2] scsi: ufs: Enable power management for wlun
To:     Bart Van Assche <bvanassche@acm.org>, cang@codeaurora.org,
        martin.petersen@oracle.com, adrian.hunter@intel.com,
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 <f111e363-c709-fe3c-65da-450c9e9e3408@acm.org>
From:   "Asutosh Das (asd)" <asutoshd@codeaurora.org>
Message-ID: <9ae35c14-f8aa-a181-2259-2d32bd2c1f07@codeaurora.org>
Date:   Fri, 16 Apr 2021 11:21:48 -0700
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On 4/15/2021 4:11 PM, Bart Van Assche wrote:
> On 4/14/21 11:58 AM, Asutosh Das wrote:
>> [ ... ]
> 
Hi Bart,
Thanks for the comments. I will fix the comments in the next version.

> The following code is executed before ufshcd_async_scan() is called:
> 
> 	dev = hba->dev;
> 	[ ... ]
> 	/* Hold auto suspend until async scan completes */
> 	pm_runtime_get_sync(dev);
> 
That would only keep the hba runtime resumed. At this point of time the 
luns are not detected yet.
> and the following code occurs in ufshcd_add_lus():
> 
> 	pm_runtime_put_sync(hba->dev);
> 
> Isn't that sufficient to postpone enabling of runtime PM until LUN
> scanning has finished? Or in other words, is adding a
> pm_runtime_get_noresume() call in ufshcd_slave_configure() really necessary?
> 
Yes, because the supplier (device wlun) may be suspended otherwise in 
scsi_sysfs_add_sdev().
>> @@ -4979,15 +5035,9 @@ ufshcd_transfer_rsp_status(struct ufs_hba *hba, struct ufshcd_lrb *lrbp)
>>   			 */
>>   			if (!hba->pm_op_in_progress &&
>>   			    !ufshcd_eh_in_progress(hba) &&
>> -			    ufshcd_is_exception_event(lrbp->ucd_rsp_ptr) &&
>> -			    schedule_work(&hba->eeh_work)) {
>> -				/*
>> -				 * Prevent suspend once eeh_work is scheduled
>> -				 * to avoid deadlock between ufshcd_suspend
>> -				 * and exception event handler.
>> -				 */
>> -				pm_runtime_get_noresume(hba->dev);
>> -			}
>> +			    ufshcd_is_exception_event(lrbp->ucd_rsp_ptr))
>> +				/* Flushed in suspend */
>> +				schedule_work(&hba->eeh_work);
> 
> What makes it safe to leave out the above pm_runtime_get_noresume() call?
> 
The __ufshcd_wl_suspend() would flush this work so that it doesn't run 
after suspend.
> Thanks,
> 
> Bart.
> 


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