openwrt/target/linux/bcm27xx/patches-6.6/950-0655-vc4-drm-Remove-the-clear-of-SCALER_DISPBKGND_FILL.patch

From 62bc808af174dfc9365ae54cbaf6c21f662ea4c3 Mon Sep 17 00:00:00 2001
From: Dom Cobley <popcornmix@gmail.com>
Date: Wed, 4 Oct 2023 16:02:39 +0100
Subject: [PATCH 0655/1085] vc4/drm: Remove the clear of SCALER_DISPBKGND_FILL

Since "drm/vc4: hvs: Support BCM2712 HVS" booting Pi4
with dual 4kp30 displays connected fails with:
vc4-drm gpu: [drm] *ERROR* [CRTC:107:pixelvalve-4] flip_done timed out

It has been tracked down to the referenced commit adding a
path to clear the SCALER_DISPBKGND_FILL when not required.

Dual 4kp30 works with a core clock of 297MHz when background fill
is enabled, but requires a higher value with it disabled.
320MHz still fails, while 330MHz seems okay.

Lets always enable background fill for Pi0-4.

Fixes: e84da235223d ("drm/vc4: hvs: Support BCM2712 HVS")

Signed-off-by: Dom Cobley <popcornmix@gmail.com>
---
 drivers/gpu/drm/vc4/vc4_hvs.c | 20 +++++++++-----------
 1 file changed, 9 insertions(+), 11 deletions(-)

--- a/drivers/gpu/drm/vc4/vc4_hvs.c
+++ b/drivers/gpu/drm/vc4/vc4_hvs.c
@@ -1304,27 +1304,25 @@ void vc4_hvs_atomic_flush(struct drm_crt
 	WARN_ON(!vc4_state->mm);
 	WARN_ON_ONCE(dlist_next - dlist_start != vc4_state->mm->mm_node.size);
 
-	if (enable_bg_fill) {
+	if (vc4->gen >= VC4_GEN_6) {
 		/* This sets a black background color fill, as is the case
 		 * with other DRM drivers.
 		 */
-		if (vc4->gen >= VC4_GEN_6)
+		if (enable_bg_fill)
 			HVS_WRITE(SCALER6_DISPX_CTRL1(channel),
 				  HVS_READ(SCALER6_DISPX_CTRL1(channel)) |
 				  SCALER6_DISPX_CTRL1_BGENB);
 		else
-			HVS_WRITE(SCALER_DISPBKGNDX(channel),
-				  HVS_READ(SCALER_DISPBKGNDX(channel)) |
-				  SCALER_DISPBKGND_FILL);
-	} else {
-		if (vc4->gen >= VC4_GEN_6)
 			HVS_WRITE(SCALER6_DISPX_CTRL1(channel),
 				  HVS_READ(SCALER6_DISPX_CTRL1(channel)) &
 				  ~SCALER6_DISPX_CTRL1_BGENB);
-		else
-			HVS_WRITE(SCALER_DISPBKGNDX(channel),
-				  HVS_READ(SCALER_DISPBKGNDX(channel)) &
-				  ~SCALER_DISPBKGND_FILL);
+	} else {
+		/* we can actually run with a lower core clock when background
+		 * fill is enabled on VC4_GEN_5 so leave it enabled always.
+		 */
+		HVS_WRITE(SCALER_DISPBKGNDX(channel),
+			  HVS_READ(SCALER_DISPBKGNDX(channel)) |
+			  SCALER_DISPBKGND_FILL);
 	}
 
 	/* Only update DISPLIST if the CRTC was already running and is not