drm/i915: CHV DDR DVFS support and another watermark rewrite
Turns out the VLV/CHV system agent doesn't understand memory latencies, so trying to rely on the PND deadline mechanism is not going to fly especially when DDR DVFS is enabled. Currently we try to avoid the problems by lying to the system agent about the deadlines and setting the FIFO watermarks to 8 cachelines. This however leads to bad memory self refresh residency. So in order to satosfy everyone we'll just give up on the deadline scheme and program the watermarks old school based on the worst case memory latency. I've modelled this a bit on the ILK+ approach where we compute multiple sets of watermarks for each pipe (PM2,PM5,DDR DVFS) and when merge thet appropriate one later with the watermarks from other pipes. There isn't too much to merge actually since each pipe has a totally independent FIFO (well apart from the mess with the partially shared DSPARB registers), but still decopuling the pipes from each other seems like a good idea. Eventually we'll want to perform the watermark update in two phases around the plane update to avoid underruns due to the single buffered watermark registers. But that's still in limbo for ILK+ too, so I've not gone that far yet for VLV/CHV either. Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com> Reviewed-by: NClint Taylor <Clinton.A.Taylor@intel.com> Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Showing
想要评论请 注册 或 登录