Re: [PATCH v2] scsi: ufs: Implement Auto-Hibern8 setup

[Bart Van Assche <Bart.VanAssche@wdc.com>]

On Tue, 2017-07-25 at 16:54 +0000, Potomski, MichalX wrote:
> On Tue, 2017-07-25 at 15:30 +0000, Bart Van Assche wrote:
> > Since I'm not familiar with the Auto-Hibern8 feature: what impact does it
> > have on command processing? Does it e.g. cause SCSI or TMF commands that
> > are
> > sent to the UFS device to be ignored, to fail or to time out?
> 
> Actually behavior should be transparent for all of the higher layers, since this
> shall be fully controlled by UFS Host, which will put UFS Device to Hibern8 state,
> when it has no ongoing commands to it for set up time. If there will be any command
> UFS Host should order the Device to exit Hibern8 mode and proceed normally.
> 
> Bottom line is that in model case, it shouldn't cause any of errors mentioned by you.
> There is possible throughput degradation in case, if transfers are sporadic in terms
> of timer, which we did set up, though. According to specification it also shouldn't affect
> Hibern8 states triggered by Power Management, nor any other functionality.

Hello Michal,

SCSI requests can not only be initiated by user space but also by the kernel
itself. Are SCSI UFS devices controlled by the SCSI disk (sd) driver? Will
SCSI requests submitted by sd_check_events() to a hibernated UFS device time
out and activate the SCSI error handler?

Thanks,

Bart.