The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

Thanks,
Sasha

------------------ original commit in Linus's tree ------------------

From 3d066f9547dd58329b526db44f42c487a7974703 Mon Sep 17 00:00:00 2001
From: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Date: Wed, 21 Feb 2024 12:27:31 -0500
Subject: [PATCH] drm/amd/display: Fix idle check for shared firmware state

[WHY]
We still had an instance of get_idle_state checking the PMFW scratch
register instead of the actual idle allow signal.

[HOW]
Replace it with the SW state check for whether we had allowed idle
through notify_idle.

Cc: Mario Limonciello <mario.limonciello@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
Reviewed-by: Duncan Ma <duncan.ma@amd.com>
Acked-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
---
 drivers/gpu/drm/amd/display/dc/core/dc.c | 12 +++---------
 1 file changed, 3 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/dc/core/dc.c b/drivers/gpu/drm/amd/display/dc/core/dc.c
index 613d09c42f3b9..958552a8605ff 100644
--- a/drivers/gpu/drm/amd/display/dc/core/dc.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc.c
@@ -4847,22 +4847,16 @@ void dc_exit_ips_for_hw_access(struct dc *dc)
 
 bool dc_dmub_is_ips_idle_state(struct dc *dc)
 {
-	uint32_t idle_state = 0;
-
 	if (dc->debug.disable_idle_power_optimizations)
 		return false;
 
 	if (!dc->caps.ips_support || (dc->config.disable_ips == DMUB_IPS_DISABLE_ALL))
 		return false;
 
-	if (dc->hwss.get_idle_state)
-		idle_state = dc->hwss.get_idle_state(dc);
-
-	if (!(idle_state & DMUB_IPS1_ALLOW_MASK) ||
-		!(idle_state & DMUB_IPS2_ALLOW_MASK))
-		return true;
+	if (!dc->ctx->dmub_srv)
+		return false;
 
-	return false;
+	return dc->ctx->dmub_srv->idle_allowed;
 }
 
 /* set min and max memory clock to lowest and highest DPM level, respectively */
-- 
2.43.0