[PATCH v2 25/29] arm_mpam: Probe for long/lwd mbwu counters

James Morse
2025-09-10T20:45:36Z

From: Rohit Mathew <rohit.mathew@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.

Signed-off-by: Rohit Mathew <rohit.mathew@arm.com>
Signed-off-by: James Morse <james.morse@arm.com>
Reviewed-by: Ben Horgan <ben.horgan@arm.com>
---
drivers/resctrl/mpam_devices.c | 23 ++++++++++++++++++++++-
drivers/resctrl/mpam_internal.h | 9 +++++++++
2 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
index eeb62ed94520..bae9fa9441dc 100644
--- a/drivers/resctrl/mpam_devices.c
+++ b/drivers/resctrl/mpam_devices.c
@@ -795,7 +795,7 @@ static void mpam_ris_hw_probe(struct mpam_msc_ris *ris)
dev_err_once(dev, "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 mbwumon_idr = mpam_read_partsel_reg(msc, MBWUMON_IDR);

props->num_mbwu_mon = FIELD_GET(MPAMF_MBWUMON_IDR_NUM_MON, mbwumon_idr);
@@ -805,6 +805,27 @@ static void mpam_ris_hw_probe(struct mpam_msc_ris *ris)
if (FIELD_GET(MPAMF_MBWUMON_IDR_HAS_RWBW, mbwumon_idr))
mpam_set_feature(mpam_feat_msmon_mbwu_rwbw, props);

+ /*
+ * Treat long counter and its extension, lwd as mutually
+ * exclusive feature bits. Though these are dependent
+ * fields at the implementation level, there would never
+ * be a need for mpam_feat_msmon_mbwu_44counter (long
+ * counter) and mpam_feat_msmon_mbwu_63counter (lwd)
+ * bits to be set together.
+ *
+ * mpam_feat_msmon_mbwu isn't treated as an exclusive
+ * bit as this feature bit would be used as the "front
+ * facing feature bit" for any checks related to mbwu
+ * monitors.
+ */
+ has_long = FIELD_GET(MPAMF_MBWUMON_IDR_HAS_LONG, mbwumon_idr);
+ if (props->num_mbwu_mon && has_long) {
+ if (FIELD_GET(MPAMF_MBWUMON_IDR_LWD, mbwumon_idr))
+ mpam_set_feature(mpam_feat_msmon_mbwu_63counter, props);
+ else
+ mpam_set_feature(mpam_feat_msmon_mbwu_44counter, props);
+ }
+
/* Is NRDY hardware managed? */
hw_managed = mpam_ris_hw_probe_hw_nrdy(ris, MBWU);
if (hw_managed)
diff --git a/drivers/resctrl/mpam_internal.h b/drivers/resctrl/mpam_internal.h
index 725c2aefa8a2..c190826dfbda 100644
--- a/drivers/resctrl/mpam_internal.h
+++ b/drivers/resctrl/mpam_internal.h
@@ -158,7 +158,16 @@ enum mpam_device_features {
mpam_feat_msmon_csu_capture,
mpam_feat_msmon_csu_xcl,
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_44counter/mpam_feat_msmon_mbwu_63counter
+ * as well.
+ */
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,
--
2.39.5