Hi Ben,

On 28/08/2025 17:14, Ben Horgan wrote:

On 8/22/25 16:30, James Morse wrote:

quoted

From: Rohit Mathew <redacted>

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.

quoted

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,

quoted

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

quoted

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!

quoted

+	 */
 	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@arm.com>

Thanks!

James