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Commit 8ea959a1 authored by Deepthi Dharwar's avatar Deepthi Dharwar Committed by Benjamin Herrenschmidt
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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: default avatarDeepthi Dharwar <deepthi@linux.vnet.ibm.com>
Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
parent 817deb05

arch/powerpc/include/asm/processor.h

+2 −2
Original line number Diff line number Diff line
@@ -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);

arch/powerpc/kernel/sysfs.c

+1 −1
Original line number Diff line number Diff line
@@ -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;

}

arch/powerpc/platforms/pseries/processor_idle.c

+17 −7
Original line number Diff line number Diff line
@@ -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)

{