RE: [PATCH v17 1/2] scsi: ufs: Enable power management for wlun

[Daejun Park <daejun7.park@samsung.com>]

Hi Asutosh Das,

>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>
>---
> drivers/scsi/ufs/cdns-pltfrm.c     |   2 +
> drivers/scsi/ufs/tc-dwc-g210-pci.c |   2 +
> drivers/scsi/ufs/ufs-debugfs.c     |   6 +-
> drivers/scsi/ufs/ufs-debugfs.h     |   2 +-
> drivers/scsi/ufs/ufs-exynos.c      |   2 +
> drivers/scsi/ufs/ufs-hisi.c        |   2 +
> drivers/scsi/ufs/ufs-mediatek.c    |  12 +-
> drivers/scsi/ufs/ufs-qcom.c        |   2 +
> drivers/scsi/ufs/ufs_bsg.c         |   6 +-
> drivers/scsi/ufs/ufshcd-pci.c      |  36 +--
> drivers/scsi/ufs/ufshcd.c          | 642 ++++++++++++++++++++++++++-----------
> drivers/scsi/ufs/ufshcd.h          |   6 +
> include/trace/events/ufs.h         |  20 ++
> 13 files changed, 509 insertions(+), 231 deletions(-)

In this patch, you changed pm_runtime_{get, put}_sync to scsi_autopm_{get, put}_device.
But, scsi_autopm_get_device() calls pm_runtime_put_sync() in case of error
of pm_runtime_get_sync(). So, pm_runtime_put_sync() can be called twice if
scsi_autopm_get_device has error.

Thanks,
Daejun