[Intel-gfx] [PATCH] drm/i915: Use dpcd read wake for sink crc calls.

Damien Lespiau damien.lespiau at intel.com
Wed Oct 21 13:14:19 PDT 2015

On Thu, Oct 22, 2015 at 12:01:21AM +0530, Thulasimani, Sivakumar wrote:
> On 8/25/2015 2:50 AM, Vivi, Rodrigo wrote:
> >On Mon, 2015-08-24 at 19:54 +0000, Zanoni, Paulo R wrote:
> >>Em Qui, 2015-08-20 às 16:23 -0700, Rodrigo Vivi escreveu:
> >>>Let's use a native read with retry as suggested per spec to
> >>>fix Sink CRC on SKL when PSR is enabled.
> >>>
> >>>With PSR enabled panel is probably taking more time to wake
> >>>and dpcd read is faling.
> >>Does this commit actually fix any known problem with Sink CRC? Or is
> >>it
> >>just a try? It would be nice to have this clarified in the commit
> >>message.
> >It was just a try but that made sink crc working on my SKL when PSR is
> >enabled. nothing much to add...
> SKL has new register AUX_MUTEX which should be used when accessing dpcd
> on edp. just searched the nightly code and could not find it. it might be
> the reason
> for random dpcd failures reported in the other thread.

We had patches for that back in December 2013 :)

The feedback from Art was:

    The non-software aux users are PSR/SRD and GTC.
    Better leave out the mutex for now. Hardware is going to try do the
    arbitration itself. I expect you will then need to increase any software
    timeout you may have.

Do you know if anything has changed since then?


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