[Intel-gfx] i830 watermark problems - status?

[Daniel Vetter]

On Mon, Nov 25, 2013 at 4:55 PM, Thomas Richter <thor at math.tu-berlin.de> wrote:
> Am 25.11.2013 16:23, schrieb Daniel Vetter:
>>
>> 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.
>
>
> Not a problem on my side, but it would be a "bad thing"(tm) to release a
> kernel that leaves a i830 based
> architecture essentially non-usable. Well, if you depend on a local display,
> that is. (-;

Well i830M has been broken since forever, so in a way this is just
normal enabling. Since you're the first guy to actually bother with it
I don't think the actual population of i830M users is that big ... So
imo we don't need to be in an utter hurry to rush in something which
isn't ready.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch