Re: [PATCH 1/2] ACPI: processor: Do not use C3 w/o ARB_DIS=1

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Rafael J. Wysocki wrote:
On Wed, Apr 20, 2022 at 3:44 PM Ville Syrjala
<ville.syrjala@xxxxxxxxxxxxxxx> wrote:
From: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>

commit d6b88ce2eb9d ("ACPI: processor idle: Allow playing dead in C3 state")
was supposedly just trying to enable C3 when the CPU is offlined,
but it also mistakenly enabled C3 usage without setting ARB_DIS=1
in normal idle scenarios.

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.

Cc: stable@xxxxxxxxxxxxxxx
Cc: Woody Suwalski <wsuwalski@xxxxxxxxx>
Cc: Mario Limonciello <mario.limonciello@xxxxxxx>
Cc: Richard Gong <richard.gong@xxxxxxx>
Cc: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
Fixes: d6b88ce2eb9d ("ACPI: processor idle: Allow playing dead in C3 state")
Signed-off-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
---
  drivers/acpi/processor_idle.c | 4 ++--
  1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index 4556c86c3465..54f0a1915025 100644
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -793,10 +793,10 @@ static int acpi_processor_setup_cstates(struct acpi_processor *pr)

                 state->flags = 0;
                 if (cx->type == ACPI_STATE_C1 || cx->type == ACPI_STATE_C2 ||
-                   cx->type == ACPI_STATE_C3) {
+                   cx->type == ACPI_STATE_C3)
                         state->enter_dead = acpi_idle_play_dead;
+               if (cx->type == ACPI_STATE_C1 || cx->type == ACPI_STATE_C2)
                         drv->safe_state_index = count;
-               }
                 /*
                  * Halt-induced C1 is not good for ->enter_s2idle, because it
                  * re-enables interrupts on exit.  Moreover, C1 is generally not
--
Good catch, but I would prefer doing the below which should be
equivalent (modulo GMail-induced white space breakage):

---
  drivers/acpi/processor_idle.c |    3 ++-
  1 file changed, 2 insertions(+), 1 deletion(-)

Index: linux-pm/drivers/acpi/processor_idle.c
===================================================================
--- linux-pm.orig/drivers/acpi/processor_idle.c
+++ linux-pm/drivers/acpi/processor_idle.c
@@ -795,7 +795,8 @@ 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
I have tested both solutions from Ville and Rafael, and both work OK on T40.
Clearly, since Ville has duped the issue on a non-T40 machine, the processor_power_dmi_table[] solution is incorrect.

Rafael's solution seems simpler - so I also like it more :-)

Thanks, Woody





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