2013/5/6 <ville.syrjala at linux.intel.com>: > From: Ville Syrj?l? <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 > > The watermark registers are not double buffered, so we have to be > careful when/how we update them. It might be possible to increase the > watermark level before a plane update occurs, but decreasing the > watermark must happen after the plane update has finished. Also the > FIFO split can change depending on whether a sprite is enabled or not. > > The HSW multi-pipe low power watermark feature adds another level of > complexity since the LP watermarks must be the max of all pipes at any > given time. > > All of this makes the whole idea of updating watermarks before the plane > update too difficult. Instead just always update watermarks from the > vblank interrupt. > > We track the pending and active watermark levels for each pipe > separately, and when the active levels for any pipe are updated from the > vblank interrupt, we update the merged LP watermarks as well. We also > need to track the active state of sprites and pipes alongside the > watermarks to make sure we check the merged watermarks against the correct > limits. The assumption is that if even one pipe is using a sprite we > must check the merged values against the 1:1 (or 1:5) split FIFO sizes. > > TODO: > - pre-gen5/vlv obviously > - are the IVB sprite scaling workarounds good enough or do we need > extra vbl waits there? > - lots of testing to make sure it works I wanted to see if the values computed were correct, so I compiled your gitorious tree. On Haswell, it gives a "divide error" when I try to modprobe i915.ko. -- Paulo Zanoni
