ACPI: processor: idle: fix lockup regression on 32-bit ThinkPad T40

Add and ACPI idle power level limit for 32-bit ThinkPad T40.

There is a regression on T40 introduced by commit 963c970b, starting
with kernel 5.16:

commit 963c970b65826f3c7b18c831d6a1687d951b8511
Author: Richard Gong <richard.gong@amd.com>
Date:   Wed Sep 22 08:31:16 2021 -0500

  ACPI: processor idle: Allow playing dead in C3 state

The above patch is trying to enter C3 state during init, what is causing
a T40 system freeze. I have not found a similar issue on any other of my
32-bit machines.

The fix is to add another exception to the processor_power_dmi_table[] list.
As a result the dmesg shows as expected:

[2.155398] ACPI: IBM ThinkPad T40 detected - limiting to C2 max_cstate. Override with "processor.max_cstate=9"
[2.155404] ACPI: processor limited to max C-state 2

The fix is trivial and affects only vintage T40 systems.

Fixes: 963c970b6582 ("CPI: processor idle: Allow playing dead in C3 state")
Signed-off-by: Woody Suwalski <wsuwalski@gmail.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Cc: 5.16+ <stable@vger.kernel.org> # 5.16+
[ rjw: New subject ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index 86560a28751b2f7aec9158c04d908bf1adb6b95c..f8e9fa82cb9b16d3d1d5180803fd814c349156f9 100644 (file)
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -96,6 +96,11 @@ static const struct dmi_system_id processor_power_dmi_table[] = {
          DMI_MATCH(DMI_SYS_VENDOR, "ASUSTeK Computer Inc."),
          DMI_MATCH(DMI_PRODUCT_NAME,"L8400B series Notebook PC")},
         (void *)1},
+       /* T40 can not handle C3 idle state */
+       { set_max_cstate, "IBM ThinkPad T40", {
+         DMI_MATCH(DMI_SYS_VENDOR, "IBM"),
+         DMI_MATCH(DMI_PRODUCT_NAME, "23737CU")},
+        (void *)2},
        {},
 };