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cpuidle: support multiple drivers

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With the tegra3 and the big.LITTLE [1] new architectures, several cpus
with different characteristics (latencies and states) can co-exists on the
system.

The cpuidle framework has the limitation of handling only identical cpus.

This patch removes this limitation by introducing the multiple driver support
for cpuidle.

This option is configurable at compile time and should be enabled for the
architectures mentioned above. So there is no impact for the other platforms
if the option is disabled. The option defaults to 'n'. Note the multiple drivers
support is also compatible with the existing drivers, even if just one driver is
needed, all the cpu will be tied to this driver using an extra small chunk of
processor memory.

The multiple driver support use a per-cpu driver pointer instead of a global
variable and the accessor to this variable are done from a cpu context.

In order to keep the compatibility with the existing drivers, the function
'cpuidle_register_driver' and 'cpuidle_unregister_driver' will register
the specified driver for all the cpus.

The semantic for the output of /sys/devices/system/cpu/cpuidle/current_driver
remains the same except the driver name will be related to the current cpu.

The /sys/devices/system/cpu/cpu[0-9]/cpuidle/driver/name files are added
allowing to read the per cpu driver name.

[1] http://lwn.net/Articles/481055/

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Acked-by: Peter De Schrijver <pdeschrijver@nvidia.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Daniel Lezcano
2012-10-31 16:44:48 +00:00
committed by Rafael J. Wysocki
parent 13dd52f11a
commit bf4d1b5ddb
6 changed files with 362 additions and 46 deletions
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7
include/linux/cpuidle.h
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@@ -91,7 +91,7 @@ struct cpuidle_device {
int state_count;
struct cpuidle_state_usage states_usage[CPUIDLE_STATE_MAX];
struct cpuidle_state_kobj *kobjs[CPUIDLE_STATE_MAX];
struct cpuidle_driver_kobj *kobj_driver;
struct list_head device_list;
struct kobject kobj;
struct completion kobj_unregister;
@@ -157,6 +157,10 @@ extern int cpuidle_wrap_enter(struct cpuidle_device *dev,
struct cpuidle_driver *drv, int index));
extern int cpuidle_play_dead(void);
extern struct cpuidle_driver *cpuidle_get_cpu_driver(struct cpuidle_device *dev);
extern int cpuidle_register_cpu_driver(struct cpuidle_driver *drv, int cpu);
extern void cpuidle_unregister_cpu_driver(struct cpuidle_driver *drv, int cpu);
#else
static inline void disable_cpuidle(void) { }
static inline int cpuidle_idle_call(void) { return -ENODEV; }
@@ -183,7 +187,6 @@ static inline int cpuidle_wrap_enter(struct cpuidle_device *dev,
struct cpuidle_driver *drv, int index))
{ return -ENODEV; }
static inline int cpuidle_play_dead(void) {return -ENODEV; }
#endif
#ifdef CONFIG_ARCH_NEEDS_CPU_IDLE_COUPLED