ACPI processor: force throttling state when BIOS returns incorrect value

If the BIOS reports an invalid throttling state (which seems to be
fairly common after system boot), a reset is done to state T0.
Because of a check in acpi_processor_get_throttling_ptc(), the reset
never actually gets executed, which results in the error reoccurring
on every access of for example /proc/acpi/processor/CPU0/throttling.

Add a 'force' option to acpi_processor_set_throttling() to ensure
the reset really takes effect.

Addresses http://bugzilla.kernel.org/show_bug.cgi?id=13389

This patch, together with the next one, fixes a regression introduced in
2.6.30, listed on the regression list. They have been available for 2.5
months now in bugzilla, but have not been picked up, despite various
reminders and without any reason given.

Google shows that numerous people are hitting this issue. The issue is in
itself relatively minor, but the bug in the code is clear.

The patches have been in all my kernels and today testing has shown that
throttling works correctly with the patches applied when the system
overheats (http://bugzilla.kernel.org/show_bug.cgi?id=13918#c14).

Signed-off-by: Frans Pop <elendil@planet.nl>
Acked-by: Zhang Rui <rui.zhang@intel.com>
Cc: Len Brown <lenb@kernel.org>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 2 deletions

diff --git a/include/acpi/processor.h b/include/acpi/processor.h
index baf1e0a9a7ee..740ac3ad8fd0 100644
--- a/include/acpi/processor.h
+++ b/include/acpi/processor.h
@@ -174,7 +174,7 @@ struct acpi_processor_throttling {
         cpumask_var_t shared_cpu_map;
         int (*acpi_processor_get_throttling) (struct acpi_processor * pr);
         int (*acpi_processor_set_throttling) (struct acpi_processor * pr,
-                                              int state);
+                                              int state, bool force);
 
         u32 address;
         u8 duty_offset;
@@ -321,7 +321,8 @@ static inline int acpi_processor_ppc_has_changed(struct acpi_processor *pr)
 /* in processor_throttling.c */
 int acpi_processor_tstate_has_changed(struct acpi_processor *pr);
 int acpi_processor_get_throttling_info(struct acpi_processor *pr);
-extern int acpi_processor_set_throttling(struct acpi_processor *pr, int state);
+extern int acpi_processor_set_throttling(struct acpi_processor *pr,
+                                         int state, bool force);
 extern const struct file_operations acpi_processor_throttling_fops;
 extern void acpi_processor_throttling_init(void);
 /* in processor_idle.c */