Re: [PATCH v5 04/23] PM: EM: Refactor em_pd_get_efficient_state() to be more flexible

Lukasz Luba
2023-12-19T10:57:14Z

On 12/12/23 18:49, Dietmar Eggemann wrote:
> On 29/11/2023 12:08, Lukasz Luba wrote:
>> The Energy Model (EM) is going to support runtime modification. There
>> are going to be 2 EM tables which store information. This patch aims
>> to prepare the code to be generic and use one of the tables. The function
>> will no longer get a pointer to 'struct em_perf_domain' (the EM) but
>> instead a pointer to 'struct em_perf_state' (which is one of the EM's
>> tables).
> I thought the 2 EM tables design is gone?
>
> IMHO it would be less code changes and hence a more enjoyable review
> experience if you would add the 'modifiable' feature to the existing EM
> (1) and not add (2) and then remove (1) in [21/23].

I have explained that to some other your email: such approach would
create a patch monster, touching all drivers and frameworks, to just
make sure they still can compile. This is not the right approach.

>
>
> struct em_perf_domain {
> - struct em_perf_state *table; <-- (1)
> struct em_perf_table __rcu *runtime_table; <-- (2)
>
>> Prepare em_pd_get_efficient_state() for the upcoming changes and
>> make it possible to re-use. Return an index for the best performance
>
> s/make it possible to re-use/make it possible to be re-used ?

OK

>
>> state for a given EM table. The function arguments that are introduced
>> should allow to work on different performance state arrays. The caller of
>> em_pd_get_efficient_state() should be able to use the index either
>> on the default or the modifiable EM table.
>>
>> Signed-off-by: Lukasz Luba <lukasz.luba@arm.com>
>> Reviewed-by: Daniel Lezcano <daniel.lezcano@linaro.org>
>> ---
>> include/linux/energy_model.h | 30 +++++++++++++++++-------------
>> 1 file changed, 17 insertions(+), 13 deletions(-)
>>
>> diff --git a/include/linux/energy_model.h b/include/linux/energy_model.h
>> index b9caa01dfac4..8069f526c9d8 100644
>> --- a/include/linux/energy_model.h
>> +++ b/include/linux/energy_model.h
>> @@ -175,33 +175,35 @@ void em_dev_unregister_perf_domain(struct device *dev);
>>
>> /**
>> * em_pd_get_efficient_state() - Get an efficient performance state from the EM
>> - * @pd : Performance domain for which we want an efficient frequency
>> - * @freq : Frequency to map with the EM
>> + * @state: List of performance states, in ascending order
>
> (3)
>
>> + * @nr_perf_states: Number of performance states
>> + * @freq: Frequency to map with the EM
>> + * @pd_flags: Performance Domain flags
>> *
>> * It is called from the scheduler code quite frequently and as a consequence
>> * doesn't implement any check.
>> *
>> - * Return: An efficient performance state, high enough to meet @freq
>> + * Return: An efficient performance state id, high enough to meet @freq
>> * requirement.
>> */
>> -static inline
>> -struct em_perf_state *em_pd_get_efficient_state(struct em_perf_domain *pd,
>> - unsigned long freq)
>> +static inline int
>> +em_pd_get_efficient_state(struct em_perf_state *table, int nr_perf_states,
>> + unsigned long freq, unsigned long pd_flags)
>
> (3) but em_pd_get_efficient_state(struct em_perf_state *table
> ^^^^^
> [...]

Good catch, I'll change that.