Re: [PATCH v3 8/9] scsi: ufs: Update the fast abort path in ufshcd_abort() for PM requests

[Can Guo]

Hi Bart,

On 2021-06-17 01:55, Bart Van Assche wrote:
> On 6/16/21 1:47 AM, Can Guo wrote:
> > On 2021-06-16 12:40, Bart Van Assche wrote:
> > > On 6/15/21 9:00 PM, Can Guo wrote:
> > > > 2. And say we want SCSI layer to resubmit PM requests to prevent
> > > > suspend/resume fail, we should keep retrying the PM requests (so
> > > > long as error handler can recover everything successfully),
> > > > meaning we should give them unlimited retries (which I think is a
> > > > bad idea), otherwise (if they have zero retries or limited
> > > > retries), in extreme conditions, what may happen is that error
> > > > handler can recover everything successfully every time, but all
> > > > these retries (say 3) still time out, which block the power
> > > > management for too long (retries * 60 seconds) and, most
> > > > important, when the last retry times out, scsi layer will
> > > > anyways complete the PM request (even we return DID_IMM_RETRY),
> > > > then we end up same - suspend/resume shall run concurrently with
> > > > error handler and we couldn't recover saved PM errors.
> > >
> > > Hmm ... it is not clear to me why this behavior is considered a
> > > problem?
> >
> > To me, task abort to PM requests does not worth being treated so
> > differently, after all suspend/resume may fail due to any kinds of
> > UFS errors (as I've explained so many times). My idea is to let PM
> > requests fast fail (60 seconds has passed, a broken device maybe, we
> > have reason to fail it since it is just a passthrough req) and
> > schedule UFS error handler, UFS error handler shall proceed after
> > suspend/resume fails out then start to recover everything in a safe
> > environment. Is this way not working?
> Hi Can,
>
> Thank you for the clarification. As you probably know the power
> management subsystem serializes runtime power management (RPM) and
> system suspend callbacks. I was concerned about the consequences of a
> failed RPM transition on system suspend and resume. Having taken a
> closer look at the UFS driver, I see that failed RPM transitions do not
> require special handling in the system suspend or resume callbacks. In
> other words, I'm fine with the approach of failing PM requests fast.

Thank you for your time and efforts spent on this series, I will upload
next version to address your previous comments (hope I can convince 
Trilok
to pick these up).

Thanks,

Can Guo.

> Bart.