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

[Asutosh Das (asd)]

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@xxxxxxxxxxxxxx>
> > Signed-off-by: Can Guo <cang@xxxxxxxxxxxxxx>
> > Signed-off-by: Asutosh Das <asutoshd@xxxxxxxxxxxxxx>
> > ---
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?

> 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


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