[PATCH 29/33] arm_mpam: Probe for long/lwd mbwu counters

[James Morse]

Hi Ben,

On 28/08/2025 17:14, Ben Horgan wrote:
> On 8/22/25 16:30, James Morse wrote:
>> From: Rohit Mathew <rohit.mathew at arm.com>
>>
>> mpam v0.1 and versions above v1.0 support optional long counter for
>> memory bandwidth monitoring. The MPAMF_MBWUMON_IDR register have fields
>> indicating support for long counters. As of now, a 44 bit counter
>> represented by HAS_LONG field (bit 30) and a 63 bit counter represented
>> by LWD (bit 29) can be optionally integrated. Probe for these counters
>> and set corresponding feature bits if any of these counters are present.

>> diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
>> index 11be34b54643..2ab7f127baaa 100644
>> --- a/drivers/resctrl/mpam_devices.c
>> +++ b/drivers/resctrl/mpam_devices.c
>> @@ -870,7 +870,7 @@ static void mpam_ris_hw_probe(struct mpam_msc_ris *ris)
>>  				pr_err_once("Counters are not usable because not-ready timeout was not provided by firmware.");
>>  		}
>>  		if (FIELD_GET(MPAMF_MSMON_IDR_MSMON_MBWU, msmon_features)) {
>> -			bool hw_managed;
>> +			bool has_long, hw_managed;
>>  			u32 mbwumonidr = mpam_read_partsel_reg(msc, MBWUMON_IDR);

> nit: the variable name would be more readable with an underscore,
> mwumon_idr.

Sure,


>>  
>>  			props->num_mbwu_mon = FIELD_GET(MPAMF_MBWUMON_IDR_NUM_MON, mbwumonidr);

>> diff --git a/drivers/resctrl/mpam_internal.h b/drivers/resctrl/mpam_internal.h
>> index 9a50a5432f4a..9f627b5f72a1 100644
>> --- a/drivers/resctrl/mpam_internal.h
>> +++ b/drivers/resctrl/mpam_internal.h
>> @@ -178,7 +178,15 @@ enum mpam_device_features {
>>  	mpam_feat_msmon_csu,
>>  	mpam_feat_msmon_csu_capture,
>>  	mpam_feat_msmon_csu_hw_nrdy,
>> +
>> +	/*
>> +	 * Having mpam_feat_msmon_mbwu set doesn't mean the regular 31 bit MBWU
>> +	 * counter would be used. The exact counter used is decided based on the
>> +	 * status of mpam_feat_msmon_mbwu_l/mpam_feat_msmon_mbwu_lwd as well.

> mpam_feat_msmon_mbwu_44counter/mpam_feat_msmon_mbwu_63counter

That's my fault - I hate the names for these things!


>> +	 */
>>  	mpam_feat_msmon_mbwu,
>> +	mpam_feat_msmon_mbwu_44counter,
>> +	mpam_feat_msmon_mbwu_63counter,
>>  	mpam_feat_msmon_mbwu_capture,
>>  	mpam_feat_msmon_mbwu_rwbw,
>>  	mpam_feat_msmon_mbwu_hw_nrdy,
> 
> Other than the two nits, the change looks good to me.
> 
> Reviewed-by: Ben Horgan <ben.horgan at arm.com>

Thanks!

James