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Subject[PATCH 2/2] cpufreq: powernv: Use PMSR to verify global and local pstate
Date
As fast_switch may get called in interrupt disable mode, it does not
update the global_pstate_info data structure. Hence the global_pstate_info
has stale data whenever pstate is updated through fast_swtich().

So the gpstate_timer can fire after a fast_switch() call has update
the pstates to a different value. Hence the timer handler cannot rely
on the cached values of local and global pstate and needs to read it
from the PMSR.

Signed-off-by: Akshay Adiga <akshay.adiga@linux.vnet.ibm.com>

---
drivers/cpufreq/powernv-cpufreq.c | 32 ++++++++++++++++++++++----------
1 file changed, 22 insertions(+), 10 deletions(-)

diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c
index 09a0496..57713b5 100644
--- a/drivers/cpufreq/powernv-cpufreq.c
+++ b/drivers/cpufreq/powernv-cpufreq.c
@@ -592,7 +592,8 @@ 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 +601,36 @@ 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 = (val >> (56)) & 0xFF;
+ freq_data.pstate_id = (val >> (48)) & 0xFF;
+ 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 +638,6 @@ 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 */
--
2.7.4
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