bcm27xx: add support for linux v5.15

Build system: x86_64
Build-tested: bcm2708, bcm2709, bcm2710, bcm2711
Run-tested: bcm2708/RPiB+, bcm2709/RPi3B, bcm2710/RPi3B, bcm2711/RPi4B

Signed-off-by: Marty Jones <mj8263788@gmail.com>
Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>

1 files changed, 40 insertions, 0 deletions

diff --git a/target/linux/bcm27xx/patches-5.15/950-0871-drm-vc4-kms-Use-maximum-FIFO-load-for-the-HVS-clock-.patch b/target/linux/bcm27xx/patches-5.15/950-0871-drm-vc4-kms-Use-maximum-FIFO-load-for-the-HVS-clock-.patch
new file mode 100644
index 0000000000..1ed4c9dec6
--- /dev/null
+++ b/target/linux/bcm27xx/patches-5.15/950-0871-drm-vc4-kms-Use-maximum-FIFO-load-for-the-HVS-clock-.patch
@@ -0,0 +1,40 @@
+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;