[PATCH RFC v1 3/6] arm_mpam: resctrl: track MBW max hard-limit in config

[Fenghua Yu]

Once userspace sets MB_MAXHLM schemata, the driver must program the
HARDLIM bit in MPAMCFG_MBW_MAX. Without tracking the per-domain hard-
limit state in mpam_config, bandwidth reprogramming would ignore the
schemata and leave hard limits unchanged in hardware.

Add mbw_max_hardlim to mpam_config and set MPAMCFG_MBW_MAX bit 31
(HARDLIM) when reprogramming MBW_MAX on hardware that supports hard
limiting.

Signed-off-by: Fenghua Yu <fenghuay@xxxxxxxxxx>
---
 drivers/resctrl/mpam_devices.c  | 27 ++++++++++++++++++++++++---
 drivers/resctrl/mpam_internal.h |  1 +
 2 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
index 1e56e8f3858e..7dee6617b134 100644
--- a/drivers/resctrl/mpam_devices.c
+++ b/drivers/resctrl/mpam_devices.c
@@ -1664,10 +1664,29 @@ static void mpam_reprogram_ris_partid(struct mpam_msc_ris *ris, u16 partid,
 	}
 
 	if (mpam_has_feature(mpam_feat_mbw_max, rprops)) {
-		if (mpam_has_feature(mpam_feat_mbw_max, cfg))
-			mpam_write_partsel_reg(msc, MBW_MAX, cfg->mbw_max);
-		else
+		if (mpam_has_feature(mpam_feat_mbw_max, cfg) ||
+		    mpam_has_feature(mpam_feat_mbw_max_hardlim_rw, cfg)) {
+			u32 mbw_val;
+
+			/*
+			 * HARDLIM shares MPAMCFG_MBW_MAX with the bandwidth
+			 * field. A hard-limit update does not program
+			 * bandwidth: the shadow value is not live until an
+			 * MB write, and reset leaves the register at
+			 * MPAMCFG_MBW_MAX_MAX. Keep that programmed value.
+			 */
+			if (mpam_has_feature(mpam_feat_mbw_max, cfg))
+				mbw_val = cfg->mbw_max;
+			else
+				mbw_val = MPAMCFG_MBW_MAX_MAX;
+
+			if (mpam_has_feature(mpam_feat_mbw_max_hardlim_rw, cfg) &&
+			    cfg->mbw_max_hardlim)
+				mbw_val |= MPAMCFG_MBW_MAX_HARDLIM;
+			mpam_write_partsel_reg(msc, MBW_MAX, mbw_val);
+		} else {
 			mpam_write_partsel_reg(msc, MBW_MAX, MPAMCFG_MBW_MAX_MAX);
+		}
 	}
 
 	if (mpam_has_feature(mpam_feat_mbw_prop, rprops))
@@ -2986,6 +3005,8 @@ static bool mpam_update_config(struct mpam_config *cfg,
 	maybe_update_config(cfg, mpam_feat_cpor_part, newcfg, cpbm, has_changes);
 	maybe_update_config(cfg, mpam_feat_mbw_part, newcfg, mbw_pbm, has_changes);
 	maybe_update_config(cfg, mpam_feat_mbw_max, newcfg, mbw_max, has_changes);
+	maybe_update_config(cfg, mpam_feat_mbw_max_hardlim_rw, newcfg,
+			    mbw_max_hardlim, has_changes);
 
 	return has_changes;
 }
diff --git a/drivers/resctrl/mpam_internal.h b/drivers/resctrl/mpam_internal.h
index 6be32b2cb0ab..59d04cb663da 100644
--- a/drivers/resctrl/mpam_internal.h
+++ b/drivers/resctrl/mpam_internal.h
@@ -324,6 +324,7 @@ struct mpam_config {
 	u32	cpbm;
 	u32	mbw_pbm;
 	u16	mbw_max;
+	bool	mbw_max_hardlim;
 
 	struct mpam_garbage	garbage;
 };
-- 
2.53.0