[Intel-gfx] [PATCH 1/3] drm/i915/skl+: Don't trust cached ddb values

[Maarten Lankhorst]

Op 26-05-17 om 17:15 schreef Mahesh Kumar:
> Don't trust cached DDB values. Recalculate the ddb value if cached value
> is zero.
>
> If i915 is build as a module, there may be a race condition when
> cursor_disable call comes even before intel_fbdev_initial_config.
> Which may lead to cached value being 0. And further commit will fail
> until a modeset.
>
> Signed-off-by: Mahesh Kumar <mahesh1.kumar at intel.com>
> ---
>  drivers/gpu/drm/i915/intel_pm.c | 15 ++++++++++-----
>  1 file changed, 10 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index 936eef1634c7..b67be1355e39 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -3721,6 +3721,7 @@ skl_ddb_get_pipe_allocation_limits(struct drm_device *dev,
>  	struct drm_i915_private *dev_priv = to_i915(dev);
>  	struct drm_crtc *for_crtc = cstate->base.crtc;
>  	unsigned int pipe_size, ddb_size;
> +	unsigned int active_crtcs;
>  	int nth_active_pipe;
>  
>  	if (WARN_ON(!state) || !cstate->base.active) {
> @@ -3731,10 +3732,11 @@ skl_ddb_get_pipe_allocation_limits(struct drm_device *dev,
>  	}
>  
>  	if (intel_state->active_pipe_changes)
> -		*num_active = hweight32(intel_state->active_crtcs);
> +		active_crtcs = intel_state->active_crtcs;
>  	else
> -		*num_active = hweight32(dev_priv->active_crtcs);
> +		active_crtcs = dev_priv->active_crtcs;
>  
> +	*num_active = hweight32(active_crtcs);
>  	ddb_size = INTEL_INFO(dev_priv)->ddb_size;
>  	WARN_ON(ddb_size == 0);
>  
> @@ -3754,12 +3756,15 @@ skl_ddb_get_pipe_allocation_limits(struct drm_device *dev,
>  		 * copy from old state to be sure
>  		 */
>  		*alloc = to_intel_crtc_state(for_crtc->state)->wm.skl.ddb;
> -		return;
> +		if (!skl_ddb_entry_size(alloc))
> +			DRM_DEBUG_KMS("Cached pipe DDB is 0 recalculate\n");
> +		else
> +			return;
>  	}
>  
> -	nth_active_pipe = hweight32(intel_state->active_crtcs &
> +	nth_active_pipe = hweight32(active_crtcs &
>  				    (drm_crtc_mask(for_crtc) - 1));
> -	pipe_size = ddb_size / hweight32(intel_state->active_crtcs);
> +	pipe_size = ddb_size / hweight32(active_crtcs);
>  	alloc->start = nth_active_pipe * ddb_size / *num_active;
>  	alloc->end = alloc->start + pipe_size;
>  }

I'd love it if you also add a warning somewhere for active pipe with no ddb allocation to prevent this from reoccuring in the future. :)
But with the root cause being a invalid ddb allocation at boot, won't the below one liner should fix it too, but better?

I'l ltest it when f3-kbl becomes available again.

diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index a488e068c3d6..63a47909f618 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -5051,7 +5051,7 @@ skl_compute_wm(struct drm_atomic_state *state)
 	 */
 	for_each_new_crtc_in_state(state, crtc, cstate, i)
 		changed = true;
-	if (!changed)
+	if (!changed && !to_i915(state->dev)->wm.distrust_bios_wm)
 		return 0;
 
 	/* Clear all dirty flags */