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

BugLink: https://bugs.launchpad.net/bugs/1969857
commit bfe55a1f7fd6bfede16078bf04c6250fbca11588 upstream.

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

There is a regression on T40 introduced by commit d6b88ce2, starting
with kernel 5.16:

commit d6b88ce2eb9d2698eb24451eb92c0a1649b17bb1
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: d6b88ce2eb9d ("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>
Cc: "Limonciello, Mario" <Mario.Limonciello@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index ef6762a7cdf70c0fe9006fd07be45fba9052f3fe..1fd6a4a34c15420ed81cdb6519081b719814ab2f 100644 (file)
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -95,6 +95,11 @@ 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},
        {},
 };