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cpuidle: menu: Fix menu_select() for CPUIDLE_DRIVER_STATE_START == 0

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Commit a9ceb78bc7 (cpuidle,menu: use interactivity_req to disable
polling) exposed a bug in menu_select() causing it to return -1
on systems with CPUIDLE_DRIVER_STATE_START equal to zero, although
it should have returned 0.  As a result, idle states are not entered
by CPUs on those systems.

Namely, on the systems in question data->last_state_idx is initially
equal to -1 and the above commit modified the condition that would
have caused it to be changed to 0 to be less likely to trigger which
exposed the problem.  However, setting data->last_state_idx initially
to -1 doesn't make sense at all and on the affected systems it should
always be set to CPUIDLE_DRIVER_STATE_START (ie. 0) unconditionally,
so make that happen.

Fixes: a9ceb78bc7 (cpuidle,menu: use interactivity_req to disable polling)
Reported-and-tested-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Rafael J. Wysocki 2016-01-14 23:24:22 +01:00
parent 84599238ea
commit 9c4b2867ed
1 changed files with 12 additions and 9 deletions
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21
drivers/cpuidle/governors/menu.c
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@ -294,8 +294,6 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev)
data->needs_update = 0;
}
data->last_state_idx = CPUIDLE_DRIVER_STATE_START - 1;
/* Special case when user has set very strict latency requirement */
if (unlikely(latency_req == 0))
return 0;
@ -326,14 +324,19 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev)
if (latency_req > interactivity_req)
latency_req = interactivity_req;
/*
* We want to default to C1 (hlt), not to busy polling
* unless the timer is happening really really soon.
*/
if (interactivity_req > 20 &&
!drv->states[CPUIDLE_DRIVER_STATE_START].disabled &&
dev->states_usage[CPUIDLE_DRIVER_STATE_START].disable == 0)
if (CPUIDLE_DRIVER_STATE_START > 0) {
data->last_state_idx = CPUIDLE_DRIVER_STATE_START - 1;
/*
* We want to default to C1 (hlt), not to busy polling
* unless the timer is happening really really soon.
*/
if (interactivity_req > 20 &&
!drv->states[CPUIDLE_DRIVER_STATE_START].disabled &&
dev->states_usage[CPUIDLE_DRIVER_STATE_START].disable == 0)
data->last_state_idx = CPUIDLE_DRIVER_STATE_START;
} else {
data->last_state_idx = CPUIDLE_DRIVER_STATE_START;
}
/*
* Find the idle state with the lowest power while satisfying