On Tue, Feb 10, 2015 at 03:28:26PM +0200, ville.syrjala@xxxxxxxxxxxxxxx wrote: > From: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> > > Assuming the PND deadline mechanism works reasonably we should do > memory requests as early as possible so that PND has schedule the > requests more intelligently. Currently we're still calculating > the watermarks as if VLV/CHV are identical to g4x, which isn't > the case. > > The current code also seems to calculate insufficient watermarks > and hence we're seeing some underruns, especially on high resolution > displays. > > To fix it just rip out the current code and replace is with something > that tries to utilize PND as efficiently as possible. > > We now calculate the WM watermark to trigger when the FIFO still has > 256us worth of data. 256us is the maximum deadline value supoorted by > PND, so issuing memory requests earlier would mean we probably couldn't > utilize the full FIFO as PND would attempt to return the data at > least in at least 256us. We also clamp the watermark to at least 8 > cachelines as that's the magic watermark that enabling trickle feed > would also impose. I'm assuming it matches some burst size. > > In theory we could just enable trickle feed and ignore the WM values, > except trickle feed doesn't work with max fifo mode anyway, so we'd > still need to calculate the SR watermarks. It seems cleaner to just > disable trickle feed and calculate all watermarks the same way. Also > trickle feed wouldn't account for the 256us max deadline value, thoguh > that may be a moot point in non-max fifo mode sicne the FIFOs are fairly > small. > > On VLV max fifo mode can be used with either primary or sprite planes. > So the code now also checks all the planes (apart from the cursor) > when calculating the SR plane watermark. > > We don't have to worry about the WM1 watermarks since we're using the > PND deadline scheme which means the hardware ignores WM1 values. > > Signed-off-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> This patch still lacks review. Any takers? -- Ville Syrjälä Intel OTC _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
