[Intel-gfx] [4/7] drm/i915: PSR: Mask LPSP hw tracking back again.

[Brian Norris]

On Thu, Aug 20, 2015 at 05:55:41PM -0700, Rodrigo Vivi wrote:
> At the beginning it was masked to allow PSR at all.
> Than it got removed later by my
> commit 09108b90f040 ("drm/i915: PSR: Remove Low Power HW tracking mask.")
> in order to trying fixing one case reported at intel-gfx mailing list
> where we were missing screen updates when runtime_pm was enabled.
> 
> However I verified that other patch that makes flush to force
> invalidate also fixes this issue by itself.
> commit 169de1316c1e ("drm/i915: PSR: Flush means invalidate + flush")
> 
> Mainly now that we are relying more on frontbuffer tracking it is a
> good idea to mask this hw tracking again.
> 
> But besides all this above it is important to hightligh that with LPSP
> unmasked we started seeing some screen freezings as reported at fd.o.
> 
> This patch fixes the unrecoverable frozen screens reported:
> 
> Reference: https://bugs.freedesktop.org/show_bug.cgi?id=91436
> Reference: https://bugs.freedesktop.org/show_bug.cgi?id=91437
> 
> Cc: Ivan Mitev <ivan.mitev at gmail.com>
> Signed-off-by: Rodrigo Vivi <rodrigo.vivi at intel.com>

FWIW:

Tested-by: Brian Norris <briannorris at chromium.org>

After patching up another regression locally, I bisected down to commit
09108b90f040 ("drm/i915: PSR: Remove Low Power HW tracking mask.") when
searching for why I could rarely get into PSR. I guess that's intended
behavior from the commit message?

    WARNING: With this patch if snd_intel_hda driver is
    running and not releasing power well properly PSR will
    constant Exit and Performance Counter will be 0.

Anyway, I guess I'm saying I'm interested in whether there is a sane
path to getting PSR going again (without disabling sound!).

Regards,
Brian