omapdrm fixes for v4.11

Fix regressions:
 - Planes might have been left enabled
 - Scaling checks did not use the new config
 
 Also limit downscaling decimation to prevent HW underflows.
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Merge tag 'omapdrm-4.11-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tomba/linux into drm-next

omapdrm fixes for v4.11

Fix regressions:
- Planes might have been left enabled
- Scaling checks did not use the new config

Also limit downscaling decimation to prevent HW underflows.

* tag 'omapdrm-4.11-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tomba/linux:
  drm/omapdrm: dispc: Refuse x-decimation above 4 for all but 8-bit formats
  drm/omapdrm: Move commit_modeset_enables() before commit_planes()
  Revert "drm: omapdrm: Let the DRM core skip plane commit on inactive CRTCs"

drivers/gpu/drm/omapdrm/dss/dispc.c

@@ -2506,6 +2506,25 @@ static int dispc_ovl_calc_scaling_44xx(unsigned long pclk, unsigned long lclk,
 		return -EINVAL;
 	}
 
+	if (*decim_x > 4 && color_mode != OMAP_DSS_COLOR_NV12) {
+		/*
+		 * Let's disable all scaling that requires horizontal
+		 * decimation with higher factor than 4, until we have
+		 * better estimates of what we can and can not
+		 * do. However, NV12 color format appears to work Ok
+		 * with all decimation factors.
+		 *
+		 * When decimating horizontally by more that 4 the dss
+		 * is not able to fetch the data in burst mode. When
+		 * this happens it is hard to tell if there enough
+		 * bandwidth. Despite what theory says this appears to
+		 * be true also for 16-bit color formats.
+		 */
+		DSSERR("Not enough bandwidth, too much downscaling (x-decimation factor %d > 4)", *decim_x);
+
+		return -EINVAL;
+	}
+
 	*core_clk = dispc.feat->calc_core_clk(pclk, in_width, in_height,
 				out_width, out_height, mem_to_mem);
 	return 0;

drivers/gpu/drm/omapdrm/omap_crtc.c

@@ -410,13 +410,7 @@ static void omap_crtc_atomic_flush(struct drm_crtc *crtc,
 		dispc_mgr_set_gamma(omap_crtc->channel, lut, length);
 	}
 
-	/*
-	 * Only flush the CRTC if it is currently enabled. CRTCs that require a
-	 * mode set are disabled prior plane updates and enabled afterwards.
-	 * They are thus not active (regardless of what their CRTC core state
-	 * reports) and the DRM core could thus call this function even though
-	 * the CRTC is currently disabled. Do nothing in that case.
-	 */
+	/* Only flush the CRTC if it is currently enabled. */
 	if (!omap_crtc->enabled)
 		return;
 

drivers/gpu/drm/omapdrm/omap_drv.c

@@ -96,9 +96,22 @@ static void omap_atomic_complete(struct omap_atomic_state_commit *commit)
 	dispc_runtime_get();
 
 	drm_atomic_helper_commit_modeset_disables(dev, old_state);
-	drm_atomic_helper_commit_planes(dev, old_state,
-					DRM_PLANE_COMMIT_ACTIVE_ONLY);
+
+	/* With the current dss dispc implementation we have to enable
+	 * the new modeset before we can commit planes. The dispc ovl
+	 * configuration relies on the video mode configuration been
+	 * written into the HW when the ovl configuration is
+	 * calculated.
+	 *
+	 * This approach is not ideal because after a mode change the
+	 * plane update is executed only after the first vblank
+	 * interrupt. The dispc implementation should be fixed so that
+	 * it is able use uncommitted drm state information.
+	 */
 	drm_atomic_helper_commit_modeset_enables(dev, old_state);
+	omap_atomic_wait_for_completion(dev, old_state);
+
+	drm_atomic_helper_commit_planes(dev, old_state, 0);
 
 	omap_atomic_wait_for_completion(dev, old_state);