Hi,
there is a long-standing regression about new C-states not working after
disconnecting AC power from a laptop if the cpuidle driver "acpi-idle" is
used. It was reported here:
[1] https://bugzilla.kernel.org/show_bug.cgi?id=42870 (March 5th 2012)
[2] https://bugzilla.kernel.org/show_bug.cgi?id=43349 (June 7th 2012)
[3] https://lkml.org/lkml/2012/10/16/518 (October 19th 2012)
In [1] Andreas proposed a patch that initialized the missing power_usage
values from within acpi_idle in the same way as cpuidle does.
In [2] I proposed a patch to use the power values provided by ACPI to
initialize the power_usage variables.
In [3] Julius proposed a patch to call the initialization function
set_power_states() not only once, but always when the C-states change.
Currently, Daniel Lezcano seems to be working on an intrusive change of not
using the power_usage value at all for choosing a C-state:
[4] https://lkml.org/lkml/2012/12/14/155
As I could not find any of these patches in any git trees to be merged for
3.8, I propose an other, least intrusive patch for the time being. It is
attached an initializes _all_ power_usage values in the first place.
As this is a real power consumption regression since 3.2, I really ask you to
apply anything and push it to stable, too!
Kind regards,
Thomas Schlichter
>From 5296fec02cfadf10daf6395ad6b55075381b2439 Mon Sep 17 00:00:00 2001
From: Thomas Schlichter <thomas.schlichter@xxxxxx>
Date: Sun, 2 Sep 2012 14:35:34 +0200
Subject: [PATCH 1/2] Get power info before updating the C-states
acpi_processor_get_power_info() has to be called before
acpi_processor_setup_cpuidle_states() to have the latest
information available. This fixes the missing C-state information
after AC-->DC transition.
Signed-off-by: Thomas Schlichter <thomas.schlichter@xxxxxx>
---
drivers/acpi/processor_idle.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index f1a5da4..17ed60b 100644
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -1149,6 +1149,7 @@ int acpi_processor_cst_has_changed(struct acpi_processor *pr)
}
/* Populate Updated C-state information */
+ acpi_processor_get_power_info(pr);
acpi_processor_setup_cpuidle_states(pr);
/* Enable all cpuidle devices */
--
1.7.10.4
>From 5c635b3530d4f9b41811f7dde12e0d6f5f7dcc54 Mon Sep 17 00:00:00 2001
From: Thomas Schlichter <thomas.schlichter@xxxxxx>
Date: Sat, 12 Jan 2013 15:30:43 +0100
Subject: [PATCH 2/2] cpuidle: Initialize power_usage for all C-states
By now, only the power_usage values of currently available C-states are
initialized in the function set_power_states(). But if the number of C-states
increases later (e.g. when using acpi_idle and unplugging the AC power from the
laptop) the power_usage values of the new C-states stay uninitialized.
Fix this by initializing all CPUIDLE_STATE_MAX C-stages in the first place.
Signed-off-by: Thomas Schlichter <thomas.schlichter@xxxxxx>
---
drivers/cpuidle/driver.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/cpuidle/driver.c b/drivers/cpuidle/driver.c
index c2b281a..960d98d 100644
--- a/drivers/cpuidle/driver.c
+++ b/drivers/cpuidle/driver.c
@@ -37,7 +37,7 @@ static void set_power_states(struct cpuidle_driver *drv)
* an power value of -1. So we use -2, -3, etc, for other
* c-states.
*/
- for (i = CPUIDLE_DRIVER_STATE_START; i < drv->state_count; i++)
+ for (i = CPUIDLE_DRIVER_STATE_START; i < CPUIDLE_STATE_MAX; i++)
drv->states[i].power_usage = -1 - i;
}
--
1.7.10.4
