On Mon, May 11, 2015 at 04:27:40PM -0700, abhay.kumar@xxxxxxxxx wrote:
> From: Abhay <abhay.kumar@xxxxxxxxx>
>
> Current WM calculation is causing regression on SR residency.
> Recomputing WM using new formula as provided by VPG
Well, really it's the same formula that's been in use since forever for
watermarks. I think we have at least a couple of copies if that formula
in the wm code (should unify a bit at some point).
However to get DDR DVFS enabled we'll need to go quite a bit beyond
this. In the meantime I suppose we might try to just use the old formula
with some kind of pessimistic latency value (not sure where the 23usec
came from, last time I heard it was 33usec for DDR DVFS, and 11usec for
PM5). But that would probably mean we'd already need to hardcode the
drain latency to a small value. In fact the current drain latency
values we're using still seem insufficient in some cases.
>
> Change-Id: I9dbd6a7b70c84454748dee41738130934230b763
> Signed-off-by: Abhay <abhay.kumar@xxxxxxxxx>
> ---
> drivers/gpu/drm/i915/intel_pm.c | 26 +++++++++++++++-----------
> 1 file changed, 15 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index a960cdd..01a5d79 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -1546,6 +1546,13 @@ static int vlv_compute_wm(struct intel_crtc *crtc,
> int fifo_size)
> {
> int clock, entries, pixel_size;
> + uint32_t line_time = 0,buffer_wm = 0;
> +
> + /* using memory DVFS latency of 23usec */
> + int latency = 23000;
> +
> + int htotal = crtc->config.adjusted_mode.crtc_htotal;
> + int hdisplay = to_intel_crtc(crtc)->config.pipe_src_w;
>
> /*
> * FIXME the plane might have an fb
> @@ -1557,18 +1564,15 @@ static int vlv_compute_wm(struct intel_crtc *crtc,
> pixel_size = drm_format_plane_cpp(plane->base.fb->pixel_format, 0);
> clock = crtc->config.adjusted_mode.crtc_clock;
>
> - entries = DIV_ROUND_UP(clock, 1000) * pixel_size;
> + line_time = max(htotal * 1000 / clock, 1);
> +
> + /* Max FIFO size */
> + fifo_size = 96 * 1024;
> +
> + buffer_wm = (fifo_size - (((latency /line_time /1000) + 1 ) *
> + hdisplay * pixel_size));
> + return buffer_wm;
>
> - /*
> - * Set up the watermark such that we don't start issuing memory
> - * requests until we are within PND's max deadline value (256us).
> - * Idea being to be idle as long as possible while still taking
> - * advatange of PND's deadline scheduling. The limit of 8
> - * cachelines (used when the FIFO will anyway drain in less time
> - * than 256us) should match what we would be done if trickle
> - * feed were enabled.
> - */
> - return fifo_size - clamp(DIV_ROUND_UP(256 * entries, 64), 0, fifo_size - 8);
> }
>
> static bool vlv_compute_sr_wm(struct drm_device *dev,
> --
> 2.1.4
>
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@xxxxxxxxxxxxxxxxxxxxx
> http://lists.freedesktop.org/mailman/listinfo/intel-gfx
--
Ville Syrjälä
Intel OTC
_______________________________________________
Intel-gfx mailing list
Intel-gfx@xxxxxxxxxxxxxxxxxxxxx
http://lists.freedesktop.org/mailman/listinfo/intel-gfx
