openwrt/target/linux/bcm27xx/patches-6.1/950-0731-drm-vc4-hdmi-Increase-MAI-fifo-dreq-threshold.patch

From 7b3d872d5cb43e85da3c9a6406d784ccfdd59845 Mon Sep 17 00:00:00 2001
From: Dom Cobley <popcornmix@gmail.com>
Date: Fri, 21 Apr 2023 22:00:16 +0100
Subject: [PATCH] drm/vc4: hdmi: Increase MAI fifo dreq threshold

Now we wait for write responses and have a burst
size of 4, we can set the fifo threshold much higher.

Set it to 28 (of the 32 entry size) to keep fifo
fuller and reduce chance of underflow.

Signed-off-by: Dom Cobley <popcornmix@gmail.com>
---
 drivers/gpu/drm/vc4/vc4_hdmi.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

--- a/drivers/gpu/drm/vc4/vc4_hdmi.c
+++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
@@ -2555,6 +2555,7 @@ static int vc4_hdmi_audio_prepare(struct
 {
 	struct vc4_hdmi *vc4_hdmi = dev_get_drvdata(dev);
 	struct drm_device *drm = vc4_hdmi->connector.dev;
+	struct vc4_dev *vc4 = to_vc4_dev(drm);
 	struct drm_encoder *encoder = &vc4_hdmi->encoder.base;
 	unsigned int sample_rate = params->sample_rate;
 	unsigned int channels = params->channels;
@@ -2613,11 +2614,18 @@ static int vc4_hdmi_audio_prepare(struct
 					     VC4_HDMI_AUDIO_PACKET_CEA_MASK);
 
 	/* Set the MAI threshold */
-	HDMI_WRITE(HDMI_MAI_THR,
-		   VC4_SET_FIELD(0x08, VC4_HD_MAI_THR_PANICHIGH) |
-		   VC4_SET_FIELD(0x08, VC4_HD_MAI_THR_PANICLOW) |
-		   VC4_SET_FIELD(0x06, VC4_HD_MAI_THR_DREQHIGH) |
-		   VC4_SET_FIELD(0x08, VC4_HD_MAI_THR_DREQLOW));
+	if (vc4->is_vc5)
+		HDMI_WRITE(HDMI_MAI_THR,
+			VC4_SET_FIELD(0x10, VC4_HD_MAI_THR_PANICHIGH) |
+			VC4_SET_FIELD(0x10, VC4_HD_MAI_THR_PANICLOW) |
+			VC4_SET_FIELD(0x1c, VC4_HD_MAI_THR_DREQHIGH) |
+			VC4_SET_FIELD(0x1c, VC4_HD_MAI_THR_DREQLOW));
+	else
+		HDMI_WRITE(HDMI_MAI_THR,
+			VC4_SET_FIELD(0x8, VC4_HD_MAI_THR_PANICHIGH) |
+			VC4_SET_FIELD(0x8, VC4_HD_MAI_THR_PANICLOW) |
+			VC4_SET_FIELD(0x6, VC4_HD_MAI_THR_DREQHIGH) |
+			VC4_SET_FIELD(0x8, VC4_HD_MAI_THR_DREQLOW));
 
 	HDMI_WRITE(HDMI_MAI_CONFIG,
 		   VC4_HDMI_MAI_CONFIG_BIT_REVERSE |