Re: [PATCH 2/3] drm/i915/gen9: Compute data rates for all planes on first commit

[Daniel Vetter <daniel@ffwll.ch>]

On Thu, Jun 09, 2016 at 03:14:54PM -0700, Matt Roper wrote:
> When we sanitize our DDB and watermark info during the first atomic
> commit, we need to calculate the total data rate.  Since we haven't
> explicitly added the planes for each CRTC to our atomic state, the total
> data rate calculation will try to use the cached values from a previous
> commit (which are 0 since there was no previous commit); this result is
> incorrect if we inherited any active planes from the BIOS.
> 
> During our very first atomic commit, we need to explicitly add all
> active planes to the atomic state to ensure that valid data rate values
> are calculated for them.  Subsequent commits will then have valid cached
> values to fall back on.
> 
> Reported-by: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
> Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
> Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_pm.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index 0cd38ca..ba08639 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -3933,6 +3933,18 @@ skl_compute_ddb(struct drm_atomic_state *state)
>  		if (IS_ERR(cstate))
>  			return PTR_ERR(cstate);
>  
> +		/*
> +		 * If this is our first commit after hw readout, we don't have
> +		 * valid data rate values cached.  Add all planes to ensure we
> +		 * calculate a valid data rate.
> +		 */
> +		if (dev_priv->wm.distrust_bios_wm) {
> +			ret = drm_atomic_add_affected_planes(state,
> +							     &intel_crtc->base);

Again, imo should be pulled out. Other wm code probably has the exact same
bug.
-Daniel

> +			if (ret)
> +				return ret;
> +		}
> +
>  		ret = skl_allocate_pipe_ddb(cstate, ddb);
>  		if (ret)
>  			return ret;
> -- 
> 2.1.4
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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