Hi Daniel,

did you get this? (See below)?

In the meantime, I also checked with video overlays, and the minimum 
value of 6 is not yet quite optimal, higher values (lower watermarks) 
seem to do even better. From the values I get, I also estimate a minimum 
latency of about 1100 ns, the default value of 5000 is much too high for 
the i830.

There are two alternative possibilities to fix this:

a) Include in the watermark structure not only a maximum value, but also 
a minimum value and modify calculate_wm accordingly,

-and/or-

c) include a latency value in the watermark structure, setting it to
a lower value on i830.

What do you think?

Greetings,
	Thomas


-------- Original-Nachricht --------
Betreff: [PATCH] Watermark level workaround for i830
Datum: Mon, 18 Nov 2013 10:42:31 +0100
Von: Thomas Richter <thor@math.tu-berlin.de>
An: Daniel Vetter <daniel@ffwll.ch>
Kopie (CC): intel-gfx@lists.freedesktop.org

Hi Daniel, hi intel experts,

please find a patch attached concerning the watermark levels on the i830
chipsets.

I did a couple of experiments this morning and found that the watermark
on i830 may neither be
too small (i.e. the FW_BLC register values may not be too high) as
otherwise the FIFO runs try, but
for some strange reasons, the watermark may neither be too high (the
FW_BLC register must not
be too small) as otherwise the display flickers. Reasons for this are
unclear at this moment, though
the attached patch seems to remove flickering quite reliably on linear
and tiled displays.

What I should probably also report is that the watermark is set quite
too low (i.e. much too conservative)
on the R31. The computed values are 1 and 5 (for VGA and LVDS,
respectively), though the minimum
required levels are much higher, somewhere in the ballpark of 32.

Greetings,
      Thomas