Re: [PATCH v2 23/29] arm_mpam: Add mpam_msmon_read() to read monitor value

Ben Horgan
2025-09-12T15:09:03Z

Hi James,

On 9/11/25 16:46, Ben Horgan wrote:
> Hi James,
>
> On 9/10/25 21:43, James Morse wrote:
>> Reading a monitor involves configuring what you want to monitor, and
>> reading the value. Components made up of multiple MSC may need values
>> from each MSC. MSCs may take time to configure, returning 'not ready'.
>> The maximum 'not ready' time should have been provided by firmware.
>>
>> Add mpam_msmon_read() to hide all this. If (one of) the MSC returns
>> not ready, then wait the full timeout value before trying again.
>>
>> CC: Shanker Donthineni <sdonthineni@nvidia.com>
>> Signed-off-by: James Morse <james.morse@arm.com>
>> ---
>> Changes since v1:
>> * Added XCL support.
>> * Merged FLT/CTL constants.
>> * a spelling mistake in a comment.
>> * moved structrues around.
>> ---
>> drivers/resctrl/mpam_devices.c | 226 ++++++++++++++++++++++++++++++++
>> drivers/resctrl/mpam_internal.h | 19 +++
>> 2 files changed, 245 insertions(+)
>>
>> diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
>> index cf190f896de1..1543c33c5d6a 100644
>> --- a/drivers/resctrl/mpam_devices.c
>> +++ b/drivers/resctrl/mpam_devices.c
>> +
>> +static void gen_msmon_ctl_flt_vals(struct mon_read *m, u32 *ctl_val,
>> + u32 *flt_val)
>> +{
>> + struct mon_cfg *ctx = m->ctx;
>> +
>> + /*
>> + * For CSU counters its implementation-defined what happens when not
>> + * filtering by partid.
>> + */
>> + *ctl_val |= MSMON_CFG_x_CTL_MATCH_PARTID;
>> +
>> + *flt_val = FIELD_PREP(MSMON_CFG_x_FLT_PARTID, ctx->partid);
>> + if (m->ctx->match_pmg) {
>> + *ctl_val |= MSMON_CFG_x_CTL_MATCH_PMG;
>> + *flt_val |= FIELD_PREP(MSMON_CFG_x_FLT_PMG, ctx->pmg);
>> + }
>> +
>> + switch (m->type) {
>> + case mpam_feat_msmon_csu:
>> + *ctl_val = MSMON_CFG_CSU_CTL_TYPE_CSU;
>> +
>> + if (mpam_has_feature(mpam_feat_msmon_csu_xcl, &m->ris->props))
>> + *flt_val |= FIELD_PREP(MSMON_CFG_CSU_FLT_XCL,
>> + ctx->csu_exclude_clean);
>> +
>> + break;
>> + case mpam_feat_msmon_mbwu:
>> + *ctl_val = MSMON_CFG_MBWU_CTL_TYPE_MBWU;

As you mentioned offline, this zeroes the other bits in *ctl_val.

Thanks,

Ben