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Date:   Tue, 2 Mar 2021 08:20:10 -0800
From:   Asutosh Das <asutoshd@codeaurora.org>
To:     Adrian Hunter <adrian.hunter@intel.com>
Cc:     cang@codeaurora.org, martin.petersen@oracle.com,
        linux-scsi@vger.kernel.org, linux-arm-msm@vger.kernel.org,
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Subject: Re: [PATCH v9 1/2] scsi: ufs: Enable power management for wlun
Message-ID: <20210302162010.GH12147@stor-presley.qualcomm.com>
References: <cover.1614655058.git.asutoshd@codeaurora.org>
 <b291bb65fadc9c828cbcb4ffb81cfa1ee47b82be.1614655058.git.asutoshd@codeaurora.org>
 <d17e52e0-cb50-50ee-accb-458b318014e5@intel.com>
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On Tue, Mar 02 2021 at 06:14 -0800, Adrian Hunter wrote:
>On 2/03/21 5:21 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 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>
>> ---
>
>Now we need either to move the suspend/resume vops from
>ufshcd_suspend/resume to __ufshcd_wl_suspend/resume, assuming that
>would work for existing implementations of those callbacks,
>or otherwise create new vops ->wl_suspend() / ->wl_resume(), and
>then split the existing implementations of those callbacks.
>
>ufs_intel_resume() now needs to be invoked from __ufshcd_wl_resume().
>I am not sure about the others:
>
>	exynos_ufs_suspend()
>	exynos_ufs_resume()
>	ufs_hisi_suspend()
>	ufs_hisi_resume()
>	ufs_mtk_suspend()
>	ufs_mtk_resume()
>	ufs_qcom_suspend()
>	ufs_qcom_resume()
>

Thanks. I'll change this in the next version.

-asd