Re: i830 watermark problems - status?

Daniel Vetter
2013-11-25T15:22:52Z

On Mon, Nov 25, 2013 at 04:14:12PM +0100, Thomas Richter wrote:
> Hi Daniel, hi group,
>
> just being curious - what is the status of the i830 watermark
> problems, i.e. the state of affairs
> concerning that the i830 does not allow the maximum watermark value,
> but requires a "headroom" of eight entries to
> avoid flickering.
>
> I provided a patch for this a while ago, but this seems to go
> nowhere. Just to remind you: The current code does not create
> a stable image on i830 based devices, even if only an internal
> display is connected.
>
> I provided two possible attacks to the problem: A quick and dirty
> method which checks for the maximum value for
> i830 manually, or an overall solution which adds a "minimum"
> watermark value for all supported chipsets.
>
> Please let me know how to proceed.

I seem to be too swamped with firedrills and bugs atm to get the polished
version in. The problem with just a quick hack is that we still need to
switch i830M to the dual-pipe watermark function, and somehow my patch to
do so seems to be broken. At least you've said that the kernel still seems
to hit the single-watermark version of the function.

So atm I'm a bit stalled on this :( But if you can track this down I'd go
with a quick hack to enforce the minimum of 8 or so in the dual-pipe
watermark function shared by gen2/3.
-Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch