[Bug 100572] [SKL dmc] Headless mode media transcoding is 20-30% slower comparing to connected monitor use case

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=100572

--- Comment #27 from Tvrtko Ursulin <tvrtko.ursulin at linux.intel.com> ---
(In reply to Imre Deak from comment #26)
> (In reply to Tvrtko Ursulin from comment #25)
> > One of the experiments Animesh asked me to do was to look at the state of
> > the DC_STATE_EN register at runtime.
> > 
> > It looked that it had reverted to a value other than what was programmed by
> > i915. On top of that, it looked impossible to manually modify it at runtime.
> > 
> > The value it is reverting to was DC_STATE_EN_UPTO_DC6, regardless of whether
> > the driver has programmed DC_STATE_EN_UPTO_DC5 or DC_STATE_EN_UPTO_DC5 |
> > DC_STATE_EN_UPTO_DC6.
> > 
> > This coupled with a comment in gen9_write_dc_state makes me suspicious
> > whether DMC is not doing things behind the drivers back?
> 
> We don't use DC5 on SKL normally only DC6. Did you boot with i915.enable_dc
> set to something non-default?

Not via the param but on Animesh'es suggestion I had the gen9_write_dc_state
modified to only ever program DC_STATE_EN_UPTO_DC5, if non zero state was
passed in. Even after that the read back from DC_STATE_EN at runtime was
DC_STATE_EN_UPTO_DC6. But during programming the read-back was getting the
programmed value. So I guess some time after the initial programming it gets
modified by someone. And I couldn't find any other place in i915 which would do
it. Which is why I thought it could be DMC.

-- 
You are receiving this mail because:
You are the QA Contact for the bug.
You are on the CC list for the bug.
You are the assignee for the bug.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.freedesktop.org/archives/intel-gfx-bugs/attachments/20170502/c4911859/attachment.html>