[Intel-gfx] [RFC][PATCH 1/1] drm/i915: Rewrite ILK+ watermark handling

Ville Syrjälä ville.syrjala at linux.intel.com
Fri May 10 09:14:18 CEST 2013

On Thu, May 09, 2013 at 12:09:30PM -0700, Jesse Barnes wrote:
> On Mon,  6 May 2013 16:45:52 +0300
> ville.syrjala at linux.intel.com wrote:
> > From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > 
> > Rewrite the ILK+ watermark code to allow:
> > - updating the watermarks safely (to avoid underruns)
> > - pre-computing watermarks (will help with atomic modest and pageflip)
> > - enabling LP1+ watermarks for HSW multi-pipe scenarios
> This looks like the right way to go long term.  But Paulo's patches for
> HSW are fairly small and make things better immediately, so we should
> probably get them in first.

Agreed. I'll try to review them properly soon, so far I just glanced at

> This one needs to be split up somehow so we can review it better like
> you mention in the TODO.
> Another thing that I used when doing the WM code way back when was to
> port it to userspace and run through various configs to make sure the
> values were all sane.  Might be nice if we could do that easily
> somehow, maybe with an #ifdef or putting all the wm stuff into a
> separate file.

Actually I had this stuff running in user space first :)

It's not that hard to implement the required stubs to get some drm
file to compile in userland. I did it already for drm_edid.c (stuff
that I've neglected to publish anywhere). I've not tried it for i915
code, and I suppose it may be a bit more work. Splitting the watermark
stuff into a separate file could help a bit though.

Ville Syrjälä
Intel OTC

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