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SubjectRe: [PATCH 2/2] cpuidle / menu: Return error code if there are no suitable states
On 04/29/2014 01:28 AM, Rafael J. Wysocki wrote:
> On Monday, April 28, 2014 01:14:32 PM Daniel Lezcano wrote:
>> On 04/27/2014 02:55 PM, Rafael J. Wysocki wrote:
>>> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>>>
>>> If there is a PM QoS latency limit and all of the sufficiently shallow
>>> C-states are disabled, the cpuidle menu governor returns 0 which on
>>> some systems is CPUIDLE_DRIVER_STATE_START and shouldn't be returned
>>> if that C-state has been disabled.
>>>
>>> Fix the issue by modifying the menu governor to return an error code
>>> in such situations.
>>>
>>> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>>> ---
>>> drivers/cpuidle/governors/menu.c | 2 +-
>>> include/linux/cpuidle.h | 2 ++
>>> 2 files changed, 3 insertions(+), 1 deletion(-)
>>>
>>> Index: linux-pm/drivers/cpuidle/governors/menu.c
>>> ===================================================================
>>> --- linux-pm.orig/drivers/cpuidle/governors/menu.c
>>> +++ linux-pm/drivers/cpuidle/governors/menu.c
>>> @@ -296,7 +296,7 @@ static int menu_select(struct cpuidle_dr
>>> data->needs_update = 0;
>>> }
>>>
>>> - data->last_state_idx = 0;
>>> + data->last_state_idx = CPUIDLE_DRIVER_STATE_POLL;
>>>
>>> /* Special case when user has set very strict latency requirement */
>>> if (unlikely(latency_req == 0))
>>> Index: linux-pm/include/linux/cpuidle.h
>>> ===================================================================
>>> --- linux-pm.orig/include/linux/cpuidle.h
>>> +++ linux-pm/include/linux/cpuidle.h
>>> @@ -217,8 +217,10 @@ static inline int cpuidle_register_gover
>>>
>>> #ifdef CONFIG_ARCH_HAS_CPU_RELAX
>>> #define CPUIDLE_DRIVER_STATE_START 1
>>> +#define CPUIDLE_DRIVER_STATE_POLL 0
>>> #else
>>> #define CPUIDLE_DRIVER_STATE_START 0
>>> +#define CPUIDLE_DRIVER_STATE_POLL (-ENXIO)
>>> #endif
>>>
>>> #endif /* _LINUX_CPUIDLE_H */
>>
>> Hi Rafael,
>>
>> CPUIDLE_DRIVER_STATE_START is only for x86. It introduces some confusion
>> in the code.
>
> I won't disagree with that.
>
>> As only two drivers are concerned by it, wouldn't make
>> sense to add the poll state to those driver directly instead of having
>> the code hacked around ? (eg. insert the poll state in the common
>> cpuidle code).
>
> Well, what about initializing data->last_state_idx to
> (CPUIDLE_DRIVER_STATE_START - 1) in menu_select() instead of introducing the
> new symbol for the time being and getting rid of CPUIDLE_DRIVER_STATE_START
> separately?

+1


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