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

M. Bergo
2025-04-27T18:37:51Z

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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@lenovo.com>

Signed-off-by: Marcus Bergo <marcusbergo@gmail.com>

---

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);

}

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