Message-Id: <20251017185645.26604-14-james.morse@arm.com>
Date: Fri, 17 Oct 2025 18:56:29 +0000
From: James Morse <james.morse@....com>
To: linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-acpi@...r.kernel.org
Cc: James Morse <james.morse@....com>,
	D Scott Phillips OS <scott@...amperecomputing.com>,
	carl@...amperecomputing.com,
	lcherian@...vell.com,
	bobo.shaobowang@...wei.com,
	tan.shaopeng@...itsu.com,
	baolin.wang@...ux.alibaba.com,
	Jamie Iles <quic_jiles@...cinc.com>,
	Xin Hao <xhao@...ux.alibaba.com>,
	peternewman@...gle.com,
	dfustini@...libre.com,
	amitsinght@...vell.com,
	David Hildenbrand <david@...hat.com>,
	Dave Martin <dave.martin@....com>,
	Koba Ko <kobak@...dia.com>,
	Shanker Donthineni <sdonthineni@...dia.com>,
	fenghuay@...dia.com,
	baisheng.gao@...soc.com,
	Jonathan Cameron <jonathan.cameron@...wei.com>,
	Rob Herring <robh@...nel.org>,
	Rohit Mathew <rohit.mathew@....com>,
	Rafael Wysocki <rafael@...nel.org>,
	Len Brown <lenb@...nel.org>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Hanjun Guo <guohanjun@...wei.com>,
	Sudeep Holla <sudeep.holla@....com>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Danilo Krummrich <dakr@...nel.org>,
	Jeremy Linton <jeremy.linton@....com>,
	Gavin Shan <gshan@...hat.com>,
	Dave Martin <Dave.Martin@....com>
Subject: [PATCH v3 13/29] arm_mpam: Probe the hardware features resctrl supports

Expand the probing support with the control and monitor types
we can use with resctrl.

CC: Dave Martin <Dave.Martin@....com>
Signed-off-by: James Morse <james.morse@....com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@...wei.com>
Reviewed-by: Fenghua Yu <fenghuay@...dia.com>
Tested-by: Fenghua Yu <fenghuay@...dia.com>
---
Changes since v2:
 * Moved some feature enum values that resctrl doesn't support to a later
   patch.
 * Swapped mpam_has_feature() out for the macro version that is used later.

Changes since v1:
 * added an underscore to a variable name.

Changes since RFC:
 * Made mpam_ris_hw_probe_hw_nrdy() more in C.
 * Added static assert on features bitmap size.
---
 drivers/resctrl/mpam_devices.c  | 147 ++++++++++++++++++++++++++++++++
 drivers/resctrl/mpam_internal.h |  33 +++++++
 2 files changed, 180 insertions(+)

diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
index 35011d3e8f1e..80c27c84dccc 100644
--- a/drivers/resctrl/mpam_devices.c
+++ b/drivers/resctrl/mpam_devices.c
@@ -142,6 +142,20 @@ static inline void _mpam_write_partsel_reg(struct mpam_msc *msc, u16 reg, u32 va
 }
 #define mpam_write_partsel_reg(msc, reg, val)  _mpam_write_partsel_reg(msc, MPAMCFG_##reg, val)
 
+static inline u32 _mpam_read_monsel_reg(struct mpam_msc *msc, u16 reg)
+{
+	mpam_mon_sel_lock_held(msc);
+	return __mpam_read_reg(msc, reg);
+}
+#define mpam_read_monsel_reg(msc, reg) _mpam_read_monsel_reg(msc, MSMON_##reg)
+
+static inline void _mpam_write_monsel_reg(struct mpam_msc *msc, u16 reg, u32 val)
+{
+	mpam_mon_sel_lock_held(msc);
+	__mpam_write_reg(msc, reg, val);
+}
+#define mpam_write_monsel_reg(msc, reg, val)   _mpam_write_monsel_reg(msc, MSMON_##reg, val)
+
 static u64 mpam_msc_read_idr(struct mpam_msc *msc)
 {
 	u64 idr_high = 0, idr_low;
@@ -544,6 +558,133 @@ static struct mpam_msc_ris *mpam_get_or_create_ris(struct mpam_msc *msc,
 	return ERR_PTR(-ENOENT);
 }
 
+/*
+ * IHI009A.a has this nugget: "If a monitor does not support automatic behaviour
+ * of NRDY, software can use this bit for any purpose" - so hardware might not
+ * implement this - but it isn't RES0.
+ *
+ * Try and see what values stick in this bit. If we can write either value,
+ * its probably not implemented by hardware.
+ */
+static bool _mpam_ris_hw_probe_hw_nrdy(struct mpam_msc_ris *ris, u32 mon_reg)
+{
+	u32 now;
+	u64 mon_sel;
+	bool can_set, can_clear;
+	struct mpam_msc *msc = ris->vmsc->msc;
+
+	if (WARN_ON_ONCE(!mpam_mon_sel_lock(msc)))
+		return false;
+
+	mon_sel = FIELD_PREP(MSMON_CFG_MON_SEL_MON_SEL, 0) |
+		  FIELD_PREP(MSMON_CFG_MON_SEL_RIS, ris->ris_idx);
+	_mpam_write_monsel_reg(msc, mon_reg, mon_sel);
+
+	_mpam_write_monsel_reg(msc, mon_reg, MSMON___NRDY);
+	now = _mpam_read_monsel_reg(msc, mon_reg);
+	can_set = now & MSMON___NRDY;
+
+	_mpam_write_monsel_reg(msc, mon_reg, 0);
+	now = _mpam_read_monsel_reg(msc, mon_reg);
+	can_clear = !(now & MSMON___NRDY);
+	mpam_mon_sel_unlock(msc);
+
+	return (!can_set || !can_clear);
+}
+
+#define mpam_ris_hw_probe_hw_nrdy(_ris, _mon_reg)			\
+	_mpam_ris_hw_probe_hw_nrdy(_ris, MSMON_##_mon_reg)
+
+static void mpam_ris_hw_probe(struct mpam_msc_ris *ris)
+{
+	int err;
+	struct mpam_msc *msc = ris->vmsc->msc;
+	struct device *dev = &msc->pdev->dev;
+	struct mpam_props *props = &ris->props;
+
+	lockdep_assert_held(&msc->probe_lock);
+	lockdep_assert_held(&msc->part_sel_lock);
+
+	/* Cache Portion partitioning */
+	if (FIELD_GET(MPAMF_IDR_HAS_CPOR_PART, ris->idr)) {
+		u32 cpor_features = mpam_read_partsel_reg(msc, CPOR_IDR);
+
+		props->cpbm_wd = FIELD_GET(MPAMF_CPOR_IDR_CPBM_WD, cpor_features);
+		if (props->cpbm_wd)
+			mpam_set_feature(mpam_feat_cpor_part, props);
+	}
+
+	/* Memory bandwidth partitioning */
+	if (FIELD_GET(MPAMF_IDR_HAS_MBW_PART, ris->idr)) {
+		u32 mbw_features = mpam_read_partsel_reg(msc, MBW_IDR);
+
+		/* portion bitmap resolution */
+		props->mbw_pbm_bits = FIELD_GET(MPAMF_MBW_IDR_BWPBM_WD, mbw_features);
+		if (props->mbw_pbm_bits &&
+		    FIELD_GET(MPAMF_MBW_IDR_HAS_PBM, mbw_features))
+			mpam_set_feature(mpam_feat_mbw_part, props);
+
+		props->bwa_wd = FIELD_GET(MPAMF_MBW_IDR_BWA_WD, mbw_features);
+		if (props->bwa_wd && FIELD_GET(MPAMF_MBW_IDR_HAS_MAX, mbw_features))
+			mpam_set_feature(mpam_feat_mbw_max, props);
+	}
+
+	/* Performance Monitoring */
+	if (FIELD_GET(MPAMF_IDR_HAS_MSMON, ris->idr)) {
+		u32 msmon_features = mpam_read_partsel_reg(msc, MSMON_IDR);
+
+		/*
+		 * If the firmware max-nrdy-us property is missing, the
+		 * CSU counters can't be used. Should we wait forever?
+		 */
+		err = device_property_read_u32(&msc->pdev->dev,
+					       "arm,not-ready-us",
+					       &msc->nrdy_usec);
+
+		if (FIELD_GET(MPAMF_MSMON_IDR_MSMON_CSU, msmon_features)) {
+			u32 csumonidr;
+
+			csumonidr = mpam_read_partsel_reg(msc, CSUMON_IDR);
+			props->num_csu_mon = FIELD_GET(MPAMF_CSUMON_IDR_NUM_MON, csumonidr);
+			if (props->num_csu_mon) {
+				bool hw_managed;
+
+				mpam_set_feature(mpam_feat_msmon_csu, props);
+
+				/* Is NRDY hardware managed? */
+				hw_managed = mpam_ris_hw_probe_hw_nrdy(ris, CSU);
+				if (hw_managed)
+					mpam_set_feature(mpam_feat_msmon_csu_hw_nrdy, props);
+			}
+
+			/*
+			 * Accept the missing firmware property if NRDY appears
+			 * un-implemented.
+			 */
+			if (err && mpam_has_feature(mpam_feat_msmon_csu_hw_nrdy, props))
+				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;
+			u32 mbwumon_idr = mpam_read_partsel_reg(msc, MBWUMON_IDR);
+
+			props->num_mbwu_mon = FIELD_GET(MPAMF_MBWUMON_IDR_NUM_MON, mbwumon_idr);
+			if (props->num_mbwu_mon)
+				mpam_set_feature(mpam_feat_msmon_mbwu, props);
+
+			/* Is NRDY hardware managed? */
+			hw_managed = mpam_ris_hw_probe_hw_nrdy(ris, MBWU);
+			if (hw_managed)
+				mpam_set_feature(mpam_feat_msmon_mbwu_hw_nrdy, props);
+
+			/*
+			 * Don't warn about any missing firmware property for
+			 * MBWU NRDY - it doesn't make any sense!
+			 */
+		}
+	}
+}
+
 static int mpam_msc_hw_probe(struct mpam_msc *msc)
 {
 	u64 idr;
@@ -587,6 +728,12 @@ static int mpam_msc_hw_probe(struct mpam_msc *msc)
 		mutex_unlock(&mpam_list_lock);
 		if (IS_ERR(ris))
 			return PTR_ERR(ris);
+		ris->idr = idr;
+
+		mutex_lock(&msc->part_sel_lock);
+		__mpam_part_sel(ris_idx, 0, msc);
+		mpam_ris_hw_probe(ris);
+		mutex_unlock(&msc->part_sel_lock);
 	}
 
 	spin_lock(&partid_max_lock);
diff --git a/drivers/resctrl/mpam_internal.h b/drivers/resctrl/mpam_internal.h
index 1afc52b36328..be9ea0aab6d2 100644
--- a/drivers/resctrl/mpam_internal.h
+++ b/drivers/resctrl/mpam_internal.h
@@ -5,6 +5,7 @@
 #define MPAM_INTERNAL_H
 
 #include <linux/arm_mpam.h>
+#include <linux/bitmap.h>
 #include <linux/cpumask.h>
 #include <linux/io.h>
 #include <linux/llist.h>
@@ -13,6 +14,7 @@
 #include <linux/sizes.h>
 #include <linux/spinlock.h>
 #include <linux/srcu.h>
+#include <linux/types.h>
 
 #define MPAM_MSC_MAX_NUM_RIS	16
 
@@ -111,6 +113,33 @@ static inline void mpam_mon_sel_lock_init(struct mpam_msc *msc)
 	raw_spin_lock_init(&msc->_mon_sel_lock);
 }
 
+/* Bits for mpam features bitmaps */
+enum mpam_device_features {
+	mpam_feat_cpor_part = 0,
+	mpam_feat_mbw_part,
+	mpam_feat_mbw_min,
+	mpam_feat_mbw_max,
+	mpam_feat_msmon,
+	mpam_feat_msmon_csu,
+	mpam_feat_msmon_csu_hw_nrdy,
+	mpam_feat_msmon_mbwu,
+	mpam_feat_msmon_mbwu_hw_nrdy,
+	MPAM_FEATURE_LAST
+};
+
+struct mpam_props {
+	DECLARE_BITMAP(features, MPAM_FEATURE_LAST);
+
+	u16			cpbm_wd;
+	u16			mbw_pbm_bits;
+	u16			bwa_wd;
+	u16			num_csu_mon;
+	u16			num_mbwu_mon;
+};
+
+#define mpam_has_feature(_feat, x)	test_bit(_feat, (x)->features)
+#define mpam_set_feature(_feat, x)	set_bit(_feat, (x)->features)
+
 struct mpam_class {
 	/* mpam_components in this class */
 	struct list_head	components;
@@ -150,6 +179,8 @@ struct mpam_vmsc {
 	/* mpam_msc_ris in this vmsc */
 	struct list_head	ris;
 
+	struct mpam_props	props;
+
 	/* All RIS in this vMSC are members of this MSC */
 	struct mpam_msc		*msc;
 
@@ -161,6 +192,8 @@ struct mpam_vmsc {
 
 struct mpam_msc_ris {
 	u8			ris_idx;
+	u64			idr;
+	struct mpam_props	props;
 
 	cpumask_t		affinity;
 
-- 
2.39.5

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