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Subject: Re: [PATCH v14 1/2] scsi: ufs: Enable power management for wlun
To:     Asutosh Das <asutoshd@codeaurora.org>, cang@codeaurora.org,
        martin.petersen@oracle.com, linux-scsi@vger.kernel.org
Cc:     linux-arm-msm@vger.kernel.org,
        Alim Akhtar <alim.akhtar@samsung.com>,
        Avri Altman <avri.altman@wdc.com>,
        "James E.J. Bottomley" <jejb@linux.ibm.com>,
        Pedro Sousa <pedrom.sousa@synopsys.com>,
        Krzysztof Kozlowski <krzk@kernel.org>,
        Stanley Chu <stanley.chu@mediatek.com>,
        Andy Gross <agross@kernel.org>,
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        Steven Rostedt <rostedt@goodmis.org>,
        Ingo Molnar <mingo@redhat.com>,
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        Lee Jones <lee.jones@linaro.org>,
        Bean Huo <beanhuo@micron.com>,
        Kiwoong Kim <kwmad.kim@samsung.com>,
        Yue Hu <huyue2@yulong.com>,
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 <16f1bcf76ff411c70fe0e3e13f84e4b0fa7d9063.1617143113.git.asutoshd@codeaurora.org>
From:   Adrian Hunter <adrian.hunter@intel.com>
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Date:   Wed, 31 Mar 2021 21:19:13 +0300
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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>
> ---

Looks good but still doesn't seem to based on the latest tree.

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 is:

	__ufshcd_wl_suspend(hba, UFS_SHUTDOWN_PM);

> +	return 0;
> +}
> +#endif