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

James Morse
2025-10-06T16:00:56Z

Hi Ben,

On 12/09/2025 16:08, Ben Horgan wrote:
> On 9/11/25 16:46, Ben Horgan wrote:
>> 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.

>>> 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.

Yes - a bug introduced during a late night, I've fixed this up.

Thanks,

James