x86 idle APM: deprecate CONFIG_APM_CPU_IDLE

We don't want to export the pm_idle function pointer to modules.
Currently CONFIG_APM_CPU_IDLE w/ CONFIG_APM_MODULE forces us to.

CONFIG_APM_CPU_IDLE is of dubious value, it runs only on 32-bit
uniprocessor laptops that are over 10 years old.  It calls into
the BIOS during idle, and is known to cause a number of machines
to fail.

Removing CONFIG_APM_CPU_IDLE and will allow us to stop exporting
pm_idle.  Any systems that were calling into the APM BIOS
at run-time will simply use HLT instead.

cc: x86@kernel.org
cc: Jiri Kosina <jkosina@suse.cz>
cc: stable@kernel.org # .39.x
Signed-off-by: Len Brown <len.brown@intel.com>

2 files changed, 12 insertions, 0 deletions

diff --git a/Documentation/feature-removal-schedule.txt b/Documentation/feature-removal-schedule.txt
index 5540615ac26c..fc505c1b4762 100644
--- a/Documentation/feature-removal-schedule.txt
+++ b/Documentation/feature-removal-schedule.txt
@@ -14,6 +14,16 @@ Who:	Len Brown <len.brown@intel.com>
 
 ---------------------------
 
+What:   CONFIG_APM_CPU_IDLE, and its ability to call APM BIOS in idle
+When:   2012
+Why:    This optional sub-feature of APM is of dubious reliability,
+        and ancient APM laptops are likely better served by calling HLT.
+        Deleting CONFIG_APM_CPU_IDLE allows x86 to stop exporting
+        the pm_idle function pointer to modules.
+Who:    Len Brown <len.brown@intel.com>
+
+----------------------------
+
 What:   PRISM54
 When:   2.6.34
 
diff --git a/arch/x86/kernel/apm_32.c b/arch/x86/kernel/apm_32.c
index 0e4f24c2a746..4c4ac32cd126 100644
--- a/arch/x86/kernel/apm_32.c
+++ b/arch/x86/kernel/apm_32.c
@@ -359,6 +359,7 @@ struct apm_user {
  * idle percentage above which bios idle calls are done
  */
 #ifdef CONFIG_APM_CPU_IDLE
+#warning deprecated CONFIG_APM_CPU_IDLE will be deleted in 2012
 #define DEFAULT_IDLE_THRESHOLD  95
 #else
 #define DEFAULT_IDLE_THRESHOLD  100
@@ -902,6 +903,7 @@ static void apm_cpu_idle(void)
         unsigned int jiffies_since_last_check = jiffies - last_jiffies;
         unsigned int bucket;
 
+        WARN_ONCE(1, "deprecated apm_cpu_idle will be deleted in 2012");
 recalc:
         if (jiffies_since_last_check > IDLE_CALC_LIMIT) {
                 use_apm_idle = 0;