[PATCH] ACPI: EC: Fix CPU frequency limitation on AMD platforms after suspend/resume

["M. Bergo" <marcusbergo@xxxxxxxxx>]

From 881e57c87b9595c186c2ca7e6d35d0a52c1a10c2 Mon Sep 17 00:00:00 2001
From: Marcus Bergo <marcusbergo@xxxxxxxxx>
Date: Sat, 19 Apr 2025 05:19:05 -0300
Subject: [PATCH] ACPI: EC: Fix CPU frequency limitation on AMD platforms 
after
 suspend/resume

Several AMD-based laptop models (Lenovo P15v Gen 3, P16v Gen 1, HP 
EliteBook 845 G10)
experience a CPU frequency limitation issue where the processor gets 
stuck at
approximately 544MHz after resuming from suspend when the power cord is 
unplugged
during sleep. This issue makes the systems practically unusable until a full
power cycle is performed.

The root cause was traced to commit b5539eb5ee70 ("ACPI: EC: Fix
acpi_ec_dispatch_gpe()") which restored the behavior of clearing the GPE
in acpi_ec_dispatch_gpe() function to prevent GPE storms. While this fix is
necessary for most platforms to prevent excessive power consumption during
suspend-to-idle, it causes problems on certain AMD platforms by interfering
with the EC's ability to properly restore power management settings 
after resume.

This patch implements a targeted workaround that:
1. Adds DMI-based detection for affected AMD platforms
2. Adds a function to check if we're in suspend-to-idle mode
3. Modifies the acpi_ec_dispatch_gpe() function to handle AMD platforms 
specially:
   - For affected AMD platforms during suspend-to-idle, it advances the
     transaction without clearing the GPE status bit
   - For all other platforms, it maintains the existing behavior of 
clearing
     the GPE status bit

Testing was performed on a Lenovo P16v Gen 1 with AMD Ryzen 7 PRO 7840HS and
confirmed that:
1. Without the patch, the CPU frequency is limited to 544MHz after the
 suspend/unplug/resume sequence
2. With the patch applied, the CPU properly scales up to its maximum 
frequency
   (5.1GHz) after the same sequence
3. No regressions were observed in other EC functionality (battery status,
   keyboard backlight, etc.)
4. Multiple suspend/resume cycles with different power states were tested
   without issues

The patch was also verified not to affect the behavior on Intel-based 
systems,
ensuring that the GPE storm prevention remains effective where needed.

Fixes: b5539eb5ee70 ("ACPI: EC: Fix acpi_ec_dispatch_gpe()")
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=218557
Reported-by: Mark Pearson <mark.pearson@xxxxxxxxxx>
Signed-off-by: Marcus Bergo <marcusbergo@xxxxxxxxx>
---
 drivers/acpi/ec.c | 66 ++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 65 insertions(+), 1 deletion(-)

diff --git a/drivers/acpi/ec.c b/drivers/acpi/ec.c
index 3c5f34892734..f3698f3c100f 100644
--- a/drivers/acpi/ec.c
+++ b/drivers/acpi/ec.c
@@ -29,6 +29,7 @@
 #include <linux/acpi.h>
 #include <linux/dmi.h>
 #include <asm/io.h>
+#include <asm/processor.h>
 #include "internal.h"
@@ -2139,6 +2140,59 @@ static bool acpi_ec_work_in_progress(struct 
acpi_ec *ec)
        return ec->events_in_progress + ec->queries_in_progress > 0;
 }
+/* List of AMD platforms with CPU frequency issues after suspend/resume */
+static const struct dmi_system_id acpi_ec_amd_freq_quirk[] = {
+       {
+  .matches = {
+    DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
+    DMI_MATCH(DMI_PRODUCT_NAME, "P15v Gen 3"),
+               },
+       },
+       {
+  .matches = {
+    DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
+    DMI_MATCH(DMI_PRODUCT_NAME, "P16v Gen 1"),
+               },
+       },
+       {
+  .matches = {
+    DMI_MATCH(DMI_SYS_VENDOR, "HP"),
+    DMI_MATCH(DMI_PRODUCT_NAME, "HP EliteBook 845 14 inch G10 Notebook 
PC"),
+               },
+       },
+       { },
+};
+
+/* Check if we're in suspend-to-idle mode */
+static bool pm_suspend_via_s2idle(void)
+{
+#ifdef CONFIG_PM_SLEEP
+       return pm_suspend_target_state == PM_SUSPEND_TO_IDLE;
+#else
+       return false;
+#endif
+}
+
+/* Check if the system is an AMD platform with the frequency quirk */
+static bool is_amd_freq_quirk_system(void)
+{
+       static int is_quirk_system = -1;
+
+       if (is_quirk_system == -1) {
+               /* Check if it's an AMD CPU */
+               if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD) {
+    is_quirk_system = 0;
+               } else {
+    /* Check if it's in the DMI quirk list */
+    is_quirk_system = dmi_check_system(acpi_ec_amd_freq_quirk) ? 1 : 0;
+               }
+       }
+
+       return is_quirk_system == 1;
+}
+
+
+
 bool acpi_ec_dispatch_gpe(void)
 {
        bool work_in_progress = false;
@@ -2172,7 +2226,17 @@ bool acpi_ec_dispatch_gpe(void)
        if (acpi_ec_gpe_status_set(first_ec)) {
pm_pr_dbg("ACPI EC GPE status set\n");
-  clear_gpe_and_advance_transaction(first_ec, false);
+               /*
+                * Special handling for AMD platforms with CPU frequency 
issues
+                * after suspend/resume. On these platforms, we need to 
advance the
+                * transaction but NOT clear the GPE status bit when in 
suspend-to-idle
+                * state to prevent CPU frequency limitation issues.
+                */
+               if (is_amd_freq_quirk_system() && pm_suspend_via_s2idle()) {
+    advance_transaction(first_ec, false);
+               } else {
+    clear_gpe_and_advance_transaction(first_ec, false);
+               }
work_in_progress = acpi_ec_work_in_progress(first_ec);
        }
--
2.43.0

Attachment: OpenPGP_0xC071F235B991FCBF.asc
Description: OpenPGP public key

Attachment: OpenPGP_signature.asc
Description: OpenPGP digital signature