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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,
        =?UTF-8?q?Ville=20Syrj=C3=A4l=C3=A4?= 
        <ville.syrjala@linux.intel.com>,
        Woody Suwalski <wsuwalski@gmail.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Subject: [PATCH 5.15 149/177] ACPI: processor: idle: Avoid falling back to C3 type C-states
Date:   Wed,  4 May 2022 18:45:42 +0200
Message-Id: <20220504153106.656086753@linuxfoundation.org>
In-Reply-To: <20220504153053.873100034@linuxfoundation.org>
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From: Ville Syrjälä <ville.syrjala@linux.intel.com>

commit fc45e55ebc58dbf622cb89ddbf797589c7a5510b upstream.

The "safe state" index is used by acpi_idle_enter_bm() to avoid
entering a C-state that may require bus mastering to be disabled
on entry in the cases when this is not going to happen.  For this
reason, it should not be set to point to C3 type of C-states, because
they may require bus mastering to be disabled on entry in principle.

This was broken by commit d6b88ce2eb9d ("ACPI: processor idle: Allow
playing dead in C3 state") which inadvertently allowed the "safe
state" index to point to C3 type of C-states.

This results in a machine that won't boot past the point when it first
enters C3. Restore the correct behaviour (either demote to C1/C2, or
use C3 but also set ARB_DIS=1).

I hit this on a Fujitsu Siemens Lifebook S6010 (P3) machine.

Fixes: d6b88ce2eb9d ("ACPI: processor idle: Allow playing dead in C3 state")
Cc: 5.16+ <stable@vger.kernel.org> # 5.16+
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Tested-by: Woody Suwalski <wsuwalski@gmail.com>
[ rjw: Subject and changelog adjustments ]
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 |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -792,7 +792,8 @@ static int acpi_processor_setup_cstates(
 		if (cx->type == ACPI_STATE_C1 || cx->type == ACPI_STATE_C2 ||
 		    cx->type == ACPI_STATE_C3) {
 			state->enter_dead = acpi_idle_play_dead;
-			drv->safe_state_index = count;
+			if (cx->type != ACPI_STATE_C3)
+				drv->safe_state_index = count;
 		}
 		/*
 		 * Halt-induced C1 is not good for ->enter_s2idle, because it