openwrt/target/linux/bcm27xx/patches-5.15/950-0871-drm-vc4-kms-Use-maximum-FIFO-load-for-the-HVS-clock-.patch

From 70887a91ef710cada7d43ac2ec93280bb53d540f Mon Sep 17 00:00:00 2001
From: Maxime Ripard <maxime@cerno.tech>
Date: Wed, 13 Apr 2022 16:22:49 +0200
Subject: [PATCH] drm/vc4: kms: Use maximum FIFO load for the HVS clock
 rate

The core clock computation takes into account both the load due to the
input (ie, planes) and its output (ie, encoders).

However, while the input load needs to consider all the planes, and thus
sum all of their associated loads, the output happens mostly in
parallel.

Therefore, we need to consider only the maximum of all the output loads,
and not the sum like we were doing. This resulted in a clock rate way
too high which could be discarded for being too high by the clock
framework.

Since recent changes, the clock framework will even downright reject it,
leading to a core clock being too low for its current needs.

Fixes: 16e101051f32 ("drm/vc4: Increase the core clock based on HVS load")
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
---
 drivers/gpu/drm/vc4/vc4_kms.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/drivers/gpu/drm/vc4/vc4_kms.c
+++ b/drivers/gpu/drm/vc4/vc4_kms.c
@@ -939,7 +939,9 @@ vc4_core_clock_atomic_check(struct drm_a
 			continue;
 
 		num_outputs++;
-		cob_rate += hvs_new_state->fifo_state[i].fifo_load;
+		cob_rate = max_t(unsigned long,
+				 hvs_new_state->fifo_state[i].fifo_load,
+				 cob_rate);
 	}
 
 	pixel_rate = load_state->hvs_load;