drm/i915: Check pipe source size when using skl+ scalers

The skl+ scalers only sample 12 bits of PIPESRC so we can't
do any plane scaling at all when the pipe source size is >4k.

Make sure the pipe source size is also below the scaler's src
size limits. Might not be 100% accurate, but should at least be
safe. We can refine the limits later if we discover that recent
hw is less restricted.

Cc: stable@vger.kernel.org
Tested-by: Ross Zwisler <zwisler@google.com>
Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/8357Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230418175528.13117-2-ville.syrjala@linux.intel.comReviewed-by: Jani Nikula <jani.nikula@intel.com>

drivers/gpu/drm/i915/display/skl_scaler.c

@@ -111,6 +111,8 @@ skl_update_scaler(struct intel_crtc_state *crtc_state, bool force_detach,
 	struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
 	const struct drm_display_mode *adjusted_mode =
 		&crtc_state->hw.adjusted_mode;
+	int pipe_src_w = drm_rect_width(&crtc_state->pipe_src);
+	int pipe_src_h = drm_rect_height(&crtc_state->pipe_src);
 	int min_src_w, min_src_h, min_dst_w, min_dst_h;
 	int max_src_w, max_src_h, max_dst_w, max_dst_h;
 
@@ -207,6 +209,21 @@ skl_update_scaler(struct intel_crtc_state *crtc_state, bool force_detach,
 		return -EINVAL;
 	}
 
+	/*
+	 * The pipe scaler does not use all the bits of PIPESRC, at least
+	 * on the earlier platforms. So even when we're scaling a plane
+	 * the *pipe* source size must not be too large. For simplicity
+	 * we assume the limits match the scaler source size limits. Might
+	 * not be 100% accurate on all platforms, but good enough for now.
+	 */
+	if (pipe_src_w > max_src_w || pipe_src_h > max_src_h) {
+		drm_dbg_kms(&dev_priv->drm,
+			    "scaler_user index %u.%u: pipe src size %ux%u "
+			    "is out of scaler range\n",
+			    crtc->pipe, scaler_user, pipe_src_w, pipe_src_h);
+		return -EINVAL;
+	}
+
 	/* mark this plane as a scaler user in crtc_state */
 	scaler_state->scaler_users |= (1 << scaler_user);
 	drm_dbg_kms(&dev_priv->drm, "scaler_user index %u.%u: "