[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 #32 from Yu Kang Ku <ykku16dev2 at gmail.com> ---
(In reply to Ville Syrjala from comment #31)
> Actually bits 31:22 look fairly interesting here. But perhaps start
> experimenting with bits 6:0 a bit instead, since that's what we do on VLV as
> well.

I experimented with bits 6:0, but all of my experiments failed.  The following
are the 5 different values I tried:
1.  val |= 3000 / 250; /* This is what VLV is using */
2.  val |= 0x16;       /* This is what you see on your BSW */
3.  val &= ~0x7f;      /* This is the minimum value just for sanity */
4.  val |= 0x1;        /* Another sanity check */
5.  val |= 0x7f;       /* This is the maximum value */

So, I've covered the normal values, as well as the extreme ones.  After every
failure, I used intel_reg to verify that the B-unit register contained the
correct value.

I then came across a BIOS setting on the BSW RVP that can disable dynamic self
refresh altogether.  So, I disabled it, but I can still reproduce the problem. 
Since it looks like self-refresh isn't a factor here, I did not bother with
bits 31:22.

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