[PATCH v1] Fix the possible wm overwriting

[Peres, Martin]

On 13/11/2018 15:08, Lisovskiy, Stanislav wrote:
> Currently whenever we attempt to recalculate
> watermarks, we assign dirty_pipes to zero,
> then compare current wm results to the recalculated
> one and if they changed we set correspondent dirty_pipes
> bit again.
> This can lead to if we have wm results overwriting and

This could lead to ... what?

> clearing dirty_pipes, so that kernel we still think that
> watermarks don't need to be updated, which then might
> lead to fifo underruns, crc mismatch and other pleasures.
> 
> Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy at intel.com>
> ---
>  drivers/gpu/drm/i915/intel_pm.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index dc034617febb..99564fa0cc4b 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -5441,9 +5441,6 @@ skl_compute_wm(struct drm_atomic_state *state)
>  	bool changed = false;
>  	int ret, i;
>  
> -	/* Clear all dirty flags */
> -	results->dirty_pipes = 0;
> -
>  	ret = skl_ddb_add_affected_pipes(state, &changed);
>  	if (ret || !changed)
>  		return ret;
> @@ -5496,6 +5493,7 @@ static void skl_atomic_update_crtc_wm(struct intel_atomic_state *state,
>  	struct drm_i915_private *dev_priv = to_i915(state->base.dev);
>  	struct skl_pipe_wm *pipe_wm = &cstate->wm.skl.optimal;
>  	const struct skl_ddb_allocation *ddb = &state->wm_results.ddb;
> +	struct skl_ddb_values *results = &state->wm_results;
>  	enum pipe pipe = crtc->pipe;
>  	enum plane_id plane_id;
>  
> @@ -5512,6 +5510,10 @@ static void skl_atomic_update_crtc_wm(struct intel_atomic_state *state,
>  			skl_write_cursor_wm(crtc, &pipe_wm->planes[plane_id],
>  					    ddb);
>  	}
> +
> +	/* Clear all dirty flags */
> +	results->dirty_pipes &= ~drm_crtc_mask(&crtc->base);
> +
>  }
>  
>  static void skl_initial_wm(struct intel_atomic_state *state,
> 

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