[Bug 97965] [BSW] External HDMI monitor suddenly shows solid color when playing Youtube video at 1080p [fifo underrun]

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=97965

--- Comment #53 from Yu Kang Ku <ykku16dev2 at gmail.com> ---
(In reply to Ville Syrjala from comment #52)
> BALIMIT0 0xb
> BALIMIT1 0xc
> BALIMIT2 0xd
> BALIMIT3 0xe
>  for each agent
>  [5:0] limit if some sort
>  [7:6] reserved

I was able to make the problem go away by configuring the following registers:
BALIMIT0 = 0x1f1f1f1f
BALIMIT1 = 0x1f1f1f1f
BALIMIT2 = 0x1f1f1f1f
BALIMIT3 = 0x1f1f1f1f

The original values for these registers are:
BALIMIT0 = 0x1f3f3f3f
BALIMIT1 = 0x3f3f3f3f
BALIMIT2 = 0x3f3f3f3f
BALIMIT3 = 0x3f3f3f3f


> 
> There are 16 agents possible it seems (agent0 to agent15). I get the
> impression that display is agent3, but there was one note somewhere
> about display possibly being agent2. But by default agent2 is not isoc
> whereas agent3 is, so that makes me think agent3 is more likely.

Based on the original values of the above registers, I think you're right about
the display being agent3.  The register descriptions mention specifically that
the display needs to use a lower value.

Overall, this experiment seems to suggest that our problem is related to
bandwidth rather than C-state latency.  What do you think?

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