Re: [PATCH 2/6] drm/i915/gen9: Only copy WM results for changed pipes to skl_hw

Matt Roper
2016-07-20T23:13:52Z

On Wed, Jul 20, 2016 at 04:59:58PM -0400, Lyude wrote:
> From: Matt Roper <matthew.d.roper@intel.com>
>
> When we write watermark values to the hardware, those values are stored
> in dev_priv->wm.skl_hw. However with recent watermark changes, the
> results structure we're copying from only contains valid watermark and
> DDB values for the pipes that are actually changing; the values for
> other pipes remain 0. Thus a blind copy of the entire skl_wm_values
> structure will clobber the values for unchanged pipes...we need to be
> more selective and only copy over the values for the changing pipes.
>
> This mistake was hidden until recently due to another bug that caused us
> to erroneously re-calculate watermarks for all active pipes rather than
> changing pipes. Only when that bug was fixed was the impact of this bug
> discovered (e.g., modesets failing with "Requested display configuration
> exceeds system watermark limitations" messages and leaving watermarks
> non-functional, even ones initiated by intel_fbdev_restore_mode).
>
> Changes since v1:
> - Add a function for copying a pipe's wm values
> (skl_copy_wm_for_pipe()) so we can reuse this later

Your changes look good to me.

Reviewed-by: Matt Roper <matthew.d.roper@intel.com>

>
> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Fixes: 734fa01f3a17 ("drm/i915/gen9: Calculate watermarks during atomic 'check' (v2)")
> Fixes: 9b6130227495 ("drm/i915/gen9: Re-allocate DDB only for changed pipes")
> Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
> Signed-off-by: Lyude <cpaul@redhat.com>
> ---
> drivers/gpu/drm/i915/intel_pm.c | 28 ++++++++++++++++++++++++++--
> 1 file changed, 26 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index fa86bea..b7d4af1 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -3966,6 +3966,24 @@ skl_compute_ddb(struct drm_atomic_state *state)
> return 0;
> }
>
> +static void
> +skl_copy_wm_for_pipe(struct skl_wm_values *dst,
> + struct skl_wm_values *src,
> + enum pipe pipe)
> +{
> + dst->wm_linetime[pipe] = src->wm_linetime[pipe];
> + memcpy(dst->plane[pipe], src->plane[pipe],
> + sizeof(dst->plane[pipe]));
> + memcpy(dst->plane_trans[pipe], src->plane_trans[pipe],
> + sizeof(dst->plane_trans[pipe]));
> +
> + dst->ddb.pipe[pipe] = src->ddb.pipe[pipe];
> + memcpy(dst->ddb.y_plane[pipe], src->ddb.y_plane[pipe],
> + sizeof(dst->ddb.y_plane[pipe]));
> + memcpy(dst->ddb.plane[pipe], src->ddb.plane[pipe],
> + sizeof(dst->ddb.plane[pipe]));
> +}
> +
> static int
> skl_compute_wm(struct drm_atomic_state *state)
> {
> @@ -4038,8 +4056,10 @@ static void skl_update_wm(struct drm_crtc *crtc)
> struct drm_device *dev = crtc->dev;
> struct drm_i915_private *dev_priv = to_i915(dev);
> struct skl_wm_values *results = &dev_priv->wm.skl_results;
> + struct skl_wm_values *hw_vals = &dev_priv->wm.skl_hw;
> struct intel_crtc_state *cstate = to_intel_crtc_state(crtc->state);
> struct skl_pipe_wm *pipe_wm = &cstate->wm.skl.optimal;
> + int pipe;
>
> if ((results->dirty_pipes & drm_crtc_mask(crtc)) == 0)
> return;
> @@ -4051,8 +4071,12 @@ static void skl_update_wm(struct drm_crtc *crtc)
> skl_write_wm_values(dev_priv, results);
> skl_flush_wm_values(dev_priv, results);
>
> - /* store the new configuration */
> - dev_priv->wm.skl_hw = *results;
> + /*
> + * Store the new configuration (but only for the pipes that have
> + * changed; the other values weren't recomputed).
> + */
> + for_each_pipe_masked(dev_priv, pipe, results->dirty_pipes)
> + skl_copy_wm_for_pipe(hw_vals, results, pipe);
>
> mutex_unlock(&dev_priv->wm.wm_mutex);
> }
> --
> 2.7.4
>

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