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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Woody Suwalski <wsuwalski@gmail.com>,
        Hans de Goede <hdegoede@redhat.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Subject: [PATCH 5.16 149/227] ACPI: processor: idle: fix lockup regression on 32-bit ThinkPad T40
Date:   Mon, 21 Feb 2022 09:49:28 +0100
Message-Id: <20220221084939.789054473@linuxfoundation.org>
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From: Woody Suwalski <wsuwalski@gmail.com>

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/acpi/processor_idle.c |    5 +++++
 1 file changed, 5 insertions(+)

--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -95,6 +95,11 @@ static const struct dmi_system_id proces
 	  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},
 	{},
 };