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cpuidle/powerpc: Fix smt_snooze_delay functionality. 

smt_snooze_delay was designed to  delay idle loop's nap entry
in the native idle code before it got  ported over to use as part of
the cpuidle framework.

A -ve value  assigned to smt_snooze_delay should result in
busy looping, in other words disabling the entry to nap state.

	- https://lists.ozlabs.org/pipermail/linuxppc-dev/2010-May/082450.html

This particular functionality can be achieved currently by
echo 1 > /sys/devices/system/cpu/cpu*/state1/disable
but it is broken when one assigns -ve value to  the smt_snooze_delay
variable either via sysfs entry or ppc64_cpu util.

This patch aims to fix this, by disabling nap state when smt_snooze_delay
variable is set to -ve value.

Signed-off-by: Deepthi Dharwar <deepthi@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This commit is contained in:
Deepthi Dharwar 2012-10-03 18:42:18 +00:00 committed by Benjamin Herrenschmidt
parent 817deb05df
commit 8ea959a17f
3 changed files with 20 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
arch/powerpc/include/asm/processor.h
View File

@ -388,9 +388,9 @@ extern int powersave_nap; /* set if nap mode can be used in idle loop */
extern void power7_nap(void);
#ifdef CONFIG_PSERIES_IDLE
extern void update_smt_snooze_delay(int snooze);
extern void update_smt_snooze_delay(int cpu, int residency);
#else
static inline void update_smt_snooze_delay(int snooze) {}
static inline void update_smt_snooze_delay(int cpu, int residency) {}
#endif
extern void flush_instruction_cache(void);

2
arch/powerpc/kernel/sysfs.c
View File

@ -50,7 +50,7 @@ static ssize_t store_smt_snooze_delay(struct device *dev,
return -EINVAL;
per_cpu(smt_snooze_delay, cpu->dev.id) = snooze;
update_smt_snooze_delay(snooze);
update_smt_snooze_delay(cpu->dev.id, snooze);
return count;
}

24
arch/powerpc/platforms/pseries/processor_idle.c
View File

@ -33,13 +33,6 @@ static int max_idle_state = MAX_IDLE_STATE_COUNT - 1;
static struct cpuidle_device __percpu *pseries_cpuidle_devices;
static struct cpuidle_state *cpuidle_state_table;
void update_smt_snooze_delay(int snooze)
{
struct cpuidle_driver *drv = cpuidle_get_driver();
if (drv)
drv->states[0].target_residency = snooze;
}
static inline void idle_loop_prolog(unsigned long *in_purr, ktime_t *kt_before)
{
@ -190,6 +183,23 @@ static struct cpuidle_state shared_states[MAX_IDLE_STATE_COUNT] = {
.enter = &shared_cede_loop },
};
void update_smt_snooze_delay(int cpu, int residency)
{
struct cpuidle_driver *drv = cpuidle_get_driver();
struct cpuidle_device *dev = per_cpu(cpuidle_devices, cpu);
if (cpuidle_state_table != dedicated_states)
return;
if (residency < 0) {
/* Disable the Nap state on that cpu */
if (dev)
dev->states_usage[1].disable = 1;
} else
if (drv)
drv->states[0].target_residency = residency;
}
static int pseries_cpuidle_add_cpu_notifier(struct notifier_block *n,
unsigned long action, void *hcpu)
{