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

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Date:   Thu, 1 Apr 2021 10:45:10 +0300
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     "Asutosh Das (asd)" <asutoshd@...eaurora.org>, cang@...eaurora.org,
        martin.petersen@...cle.com, linux-scsi@...r.kernel.org
Cc:     linux-arm-msm@...r.kernel.org,
        Alim Akhtar <alim.akhtar@...sung.com>,
        Avri Altman <avri.altman@....com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        Pedro Sousa <pedrom.sousa@...opsys.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Stanley Chu <stanley.chu@...iatek.com>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Lee Jones <lee.jones@...aro.org>,
        Bean Huo <beanhuo@...ron.com>,
        Kiwoong Kim <kwmad.kim@...sung.com>,
        Yue Hu <huyue2@...ong.com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Wei Yongjun <weiyongjun1@...wei.com>,
        Bart van Assche <bvanassche@....org>,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        Dinghao Liu <dinghao.liu@....edu.cn>,
        Jaegeuk Kim <jaegeuk@...nel.org>,
        Satya Tangirala <satyat@...gle.com>,
        open list <linux-kernel@...r.kernel.org>,
        "moderated list:ARM/SAMSUNG S3C, S5P AND EXYNOS ARM ARCHITECTURES" 
        <linux-arm-kernel@...ts.infradead.org>,
        "open list:ARM/SAMSUNG S3C, S5P AND EXYNOS ARM ARCHITECTURES" 
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        <linux-mediatek@...ts.infradead.org>
Subject: Re: [PATCH v14 1/2] scsi: ufs: Enable power management for wlun

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@...eaurora.org>
>>> Signed-off-by: Can Guo <cang@...eaurora.org>
>>> Signed-off-by: Asutosh Das <asutoshd@...eaurora.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@...eaurora.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
> 
>