[PATCH] nvme: add support for TP4084 - Time-to-Ready Enhancements

[Keith Busch]

On Fri, May 20, 2022 at 11:51:49AM +0000, Niklas Cassel wrote:
> From the CC.CRIME description:
> Changing the value of this field may cause a change in the time reported in the
> CAP.TO field. Refer to the definition of CAP.TO for more details.
> 
> The definition for CAP.TO:
> If the Controller Ready Independent of Media Enable (CC.CRIME) bit is set to ‘1’
> and the worst-case time for CSTS.RDY to change state is due to enabling the
> controller after CC.EN transitions from ‘0’ to ‘1’, then this field shall be set
> to:
> a) the value in Controller Ready Independent of Media Timeout (CRTO.CRIMT); or
> b) FFh if CRTO.CRIMT is greater than FFh.
> 
> This phrasing is quite confusing IMO.

Yes, that is rather confusing. I see you started a thread on the nvme workgroup
reflector. I hope they can clear this up.
 
> It would have been way easier if it was just separate registers for
> enable and disable timeouts...

That just makes too much sense. :) The two actions could reasonably have very
different expected times to complete, so why squeeze their timeouts into a
single value? It's not like we're running low on register space.