FAILED: patch "[PATCH] platform/x86: amd-pmc: Fix s2idle failures on certain AMD" failed to apply to 5.15-stable tree

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 <[email protected]>.

thanks,

greg k-h

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

From a602f5111fdd3d8a8ea2ac9e61f1c047d9794062 Mon Sep 17 00:00:00 2001
From: Fabrizio Bertocci <[email protected]>
Date: Mon, 29 Nov 2021 23:15:40 -0500
Subject: [PATCH] platform/x86: amd-pmc: Fix s2idle failures on certain AMD
laptops

On some AMD hardware laptops, the system fails communicating with the PMC when entering s2idle and the machine is battery powered.

Hardware description: HP Pavilion Aero Laptop 13-be0097nr
CPU: AMD Ryzen 7 5800U with Radeon Graphics
GPU: 03:00.0 VGA compatible controller [0300]: Advanced Micro Devices, Inc. [AMD/ATI] Device [1002:1638] (rev c1)

Detailed description of the problem (and investigation) here:
https://gitlab.freedesktop.org/drm/amd/-/issues/1799

Patch is a single line: reduce the polling delay in half, from 100uSec to 50uSec when waiting for a change in state from the PMC after a write command operation.

After changing the delay, I did not see a single failure on this machine (I have this fix for now more than one week and s2idle worked every single time on battery power).

index b7e50ed050a8..841c44cd64c2 100644
@@ -76,7 +76,7 @@
 #define AMD_CPU_ID_CZN			AMD_CPU_ID_RN
 #define AMD_CPU_ID_YC			0x14B5
 
-#define PMC_MSG_DELAY_MIN_US		100
+#define PMC_MSG_DELAY_MIN_US		50
 #define RESPONSE_REGISTER_LOOP_MAX	20000
 
 #define SOC_SUBSYSTEM_IP_MAX	12