Re: [RFC PATCH 20/36] arm_mpam: Probe the hardware features resctrl supports

[James Morse <james.morse@arm.com>]

Hi Ben,

On 28/07/2025 09:56, Ben Horgan wrote:
> On 7/11/25 19:36, James Morse wrote:
>> Expand the probing support with the control and monitor types
>> we can use with resctrl.

>> diff --git a/drivers/platform/arm64/mpam/mpam_internal.h b/drivers/platform/arm64/mpam/
>> mpam_internal.h
>> index 42a454d5f914..ae6fd1f62cc4 100644
>> --- a/drivers/platform/arm64/mpam/mpam_internal.h
>> +++ b/drivers/platform/arm64/mpam/mpam_internal.h
>> @@ -136,6 +136,55 @@ static inline void mpam_mon_sel_lock_held(struct mpam_msc *msc)
>>           lockdep_assert_preemption_enabled();
>>   }
>>   +/*
>> + * When we compact the supported features, we don't care what they are.
>> + * Storing them as a bitmap makes life easy.
>> + */
>> +typedef u16 mpam_features_t;
>> +
>> +/* Bits for mpam_features_t */
>> +enum mpam_device_features {
>> +    mpam_feat_ccap_part = 0,
>> +    mpam_feat_cpor_part,
>> +    mpam_feat_mbw_part,
>> +    mpam_feat_mbw_min,
>> +    mpam_feat_mbw_max,
>> +    mpam_feat_mbw_prop,
>> +    mpam_feat_msmon,
>> +    mpam_feat_msmon_csu,
>> +    mpam_feat_msmon_csu_capture,
>> +    mpam_feat_msmon_csu_hw_nrdy,
>> +    mpam_feat_msmon_mbwu,
>> +    mpam_feat_msmon_mbwu_capture,
>> +    mpam_feat_msmon_mbwu_rwbw,
>> +    mpam_feat_msmon_mbwu_hw_nrdy,
>> +    mpam_feat_msmon_capt,
>> +    MPAM_FEATURE_LAST,
>> +};
>> +#define MPAM_ALL_FEATURES      ((1 << MPAM_FEATURE_LAST) - 1)
> 
> Consider a static assert to check the type is big enough.
> 
> static_assert(BITS_PER_TYPE(mpam_features_t) >= MPAM_FEATURE_LAST);

Fancy.
There used to be an uglier one - not sure what happened to it!



Thanks,

James