Re: [PATCH 3/6] drm/i915/skl: Actually reuse wm values when pipes don't change

Matt Roper
2016-07-20T23:26:50Z

On Wed, Jul 20, 2016 at 04:59:59PM -0400, Lyude wrote:
> Up until now we've actually been making the mistake of leaving the
> watermark results for each pipe completely blank in skl_compute_wm()
> when they haven't changed, fix this.

Should this be moved before patch #1? With the existing code we don't
try to re-write watermark registers if they aren't changing, so leaving
them at zero should be safe. I think we want to make this change before
we start re-writing non-dirty watermarks. Alternatively, we could just
add the dirty bit test to the appropriate places in patch #1 and not
worry about copying over the unchanged values.

Matt

>
> Fixes: 734fa01f3a17 ("drm/i915/gen9: Calculate watermarks during atomic 'check' (v2)")
> Cc: stable@vger.kernel.org
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Cc: Daniel Vetter <daniel.vetter@intel.com>
> Cc: Radhakrishna Sripada <radhakrishna.sripada@intel.com>
> Cc: Hans de Goede <hdegoede@redhat.com> <cpaul@redhat.com>
> Cc: Matt Roper <matthew.d.roper@intel.com>
> Signed-off-by: Lyude <cpaul@redhat.com>
> ---
> drivers/gpu/drm/i915/intel_pm.c | 9 +++++++--
> 1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index b7d4af1..788db86 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -3987,10 +3987,13 @@ skl_copy_wm_for_pipe(struct skl_wm_values *dst,
> static int
> skl_compute_wm(struct drm_atomic_state *state)
> {
> + struct drm_device *dev = state->dev;
> + struct drm_i915_private *dev_priv = to_i915(dev);
> struct drm_crtc *crtc;
> struct drm_crtc_state *cstate;
> struct intel_atomic_state *intel_state = to_intel_atomic_state(state);
> struct skl_wm_values *results = &intel_state->wm_results;
> + struct skl_wm_values *hw_wm = &dev_priv->wm.skl_hw;
> struct skl_pipe_wm *pipe_wm;
> bool changed = false;
> int ret, i;
> @@ -4039,12 +4042,14 @@ skl_compute_wm(struct drm_atomic_state *state)
> if (changed)
> results->dirty_pipes |= drm_crtc_mask(crtc);
>
> - if ((results->dirty_pipes & drm_crtc_mask(crtc)) == 0)
> + if ((results->dirty_pipes & drm_crtc_mask(crtc)) == 0) {
> /* This pipe's WM's did not change */
> + skl_copy_wm_for_pipe(results, hw_wm, intel_crtc->pipe);
> continue;
> + }
>
> intel_cstate->update_wm_pre = true;
> - skl_compute_wm_results(crtc->dev, pipe_wm, results, intel_crtc);
> + skl_compute_wm_results(dev, pipe_wm, results, intel_crtc);
> }
>
> return 0;
> --
> 2.7.4
>

--
Matt Roper
Graphics Software Engineer
IoTG Platform Enabling & Development
Intel Corporation
(916) 356-2795