[PATCH v6] ufs: core: wlun suspend SSU/enter hibern8 fail recovery

[Daniil Lunev]

On Wed, Dec 21, 2022 at 4:59 PM Peter Wang (王信友)
<peter.wang at mediatek.com> wrote:
> But if without this patch when purge is onging, system IO will hang,
> this is no better.
Yes, that is why I am just pointing this out as a matter of fact, not as a bug.
It is arguable if resetting the controller in the deadlock situation is a proper
thing to do, but it might be the next best thing, so I don't argue that neither.

> So, with current design, if purge initiator do not want to see rpm
> EBUSY, then he should polling bPurgeStatus.
> What do you think?

I am actually not sure if management operations extend the timeout - they are
going through bsg interface, and I am not sure it properly re-sets the timeouts
on all possible nexus interfaces, need to check that.
But even if it does, there are two problems:
* If you make kernel be polling that parameter - it will actually make the
  application level to miss the completion code (since after querying
  completion once it will return Not Started afterwards).
* And application polling is race prone. We set runtime suspend to 100ms - so
  depending on the scheduling quirks it may miss the event.

--Daniil