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Commit 20b15b76 authored by Akshay Adiga's avatar Akshay Adiga Committed by Rafael J. Wysocki
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cpufreq: powernv: Use PMCR to verify global and local pstate 



As fast_switch() may get called with interrupt disable mode, we cannot
hold a mutex to update the global_pstate_info. So currently, fast_switch()
does not update the global_pstate_info and it will end up with stale data
whenever pstate is updated through fast_switch().

As the gpstate_timer can fire after fast_switch() has updated the pstates,
the timer handler cannot rely on the cached values of local and global
pstate and needs to read it from the PMCR.

Only gpstate_timer_handler() is affected by the stale cached pstate data
beacause either fast_switch() or target_index() routines will be called
for a given govenor, but gpstate_timer can fire after the governor has
changed to schedutil.

Signed-off-by: default avatarAkshay Adiga <akshay.adiga@linux.vnet.ibm.com>
Reviewed-by: default avatarGautham R. Shenoy <ego@linux.vnet.ibm.com>
Acked-by: default avatarViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent 60c9efb8

drivers/cpufreq/powernv-cpufreq.c

+26 −10
Original line number Diff line number Diff line
@@ -42,6 +42,10 @@ 
#define PMSR_PSAFE_ENABLE	(1UL << 30)

#define PMSR_SPR_EM_DISABLE	(1UL << 31)

#define PMSR_MAX(x)		((x >> 32) & 0xFF)

#define LPSTATE_SHIFT		48

#define GPSTATE_SHIFT		56

#define GET_LPSTATE(x)		(((x) >> LPSTATE_SHIFT) & 0xFF)

#define GET_GPSTATE(x)		(((x) >> GPSTATE_SHIFT) & 0xFF)



#define MAX_RAMP_DOWN_TIME				5120

/*
@@ -592,7 +596,8 @@ void gpstate_timer_handler(unsigned long data) 
{

	struct cpufreq_policy *policy = (struct cpufreq_policy *)data;

	struct global_pstate_info *gpstates = policy->driver_data;

	int gpstate_idx;

	int gpstate_idx, lpstate_idx;

	unsigned long val;

	unsigned int time_diff = jiffies_to_msecs(jiffies)

					- gpstates->last_sampled_time;

	struct powernv_smp_call_data freq_data;
@@ -600,21 +605,36 @@ void gpstate_timer_handler(unsigned long data) 
	if (!spin_trylock(&gpstates->gpstate_lock))

		return;



	/*

	 * If PMCR was last updated was using fast_swtich then

	 * We may have wrong in gpstate->last_lpstate_idx

	 * value. Hence, read from PMCR to get correct data.

	 */

	val = get_pmspr(SPRN_PMCR);

	freq_data.gpstate_id = (s8)GET_GPSTATE(val);

	freq_data.pstate_id = (s8)GET_LPSTATE(val);

	if (freq_data.gpstate_id  == freq_data.pstate_id) {

		reset_gpstates(policy);

		spin_unlock(&gpstates->gpstate_lock);

		return;

	}



	gpstates->last_sampled_time += time_diff;

	gpstates->elapsed_time += time_diff;

	freq_data.pstate_id = idx_to_pstate(gpstates->last_lpstate_idx);



	if ((gpstates->last_gpstate_idx == gpstates->last_lpstate_idx) ||

	    (gpstates->elapsed_time > MAX_RAMP_DOWN_TIME)) {

	if (gpstates->elapsed_time > MAX_RAMP_DOWN_TIME) {

		gpstate_idx = pstate_to_idx(freq_data.pstate_id);

		reset_gpstates(policy);

		gpstates->highest_lpstate_idx = gpstate_idx;

	} else {

		lpstate_idx = pstate_to_idx(freq_data.pstate_id);

		gpstate_idx = calc_global_pstate(gpstates->elapsed_time,

						 gpstates->highest_lpstate_idx,

						 gpstates->last_lpstate_idx);

						 lpstate_idx);

	}



	freq_data.gpstate_id = idx_to_pstate(gpstate_idx);

	gpstates->last_gpstate_idx = gpstate_idx;

	gpstates->last_lpstate_idx = lpstate_idx;

	/*

	 * If local pstate is equal to global pstate, rampdown is over

	 * So timer is not required to be queued.
@@ -622,10 +642,6 @@ void gpstate_timer_handler(unsigned long data) 
	if (gpstate_idx != gpstates->last_lpstate_idx)

		queue_gpstate_timer(gpstates);



	freq_data.gpstate_id = idx_to_pstate(gpstate_idx);

	gpstates->last_gpstate_idx = pstate_to_idx(freq_data.gpstate_id);

	gpstates->last_lpstate_idx = pstate_to_idx(freq_data.pstate_id);



	spin_unlock(&gpstates->gpstate_lock);



	/* Timer may get migrated to a different cpu on cpu hot unplug */