[PATCH RFC v4 08/18] riscv_cbqri: Add capacity controller monitoring device ops

Add the CC monitoring primitives. cbqri_init_mon_counters() pre-arms
every MCID with the Occupancy event so a subsequent READ_COUNTER
just snapshots the live counter without re-configuring the slot.

cbqri_probe_cc() leaves ctrl->mon_capable false when cacheinfo has
not given a non-zero cache_size, since the byte conversion would be
meaningless. cbqri_mon_op() takes a reg_offset and serves both CC
and BC mon_ctl registers, which share an identical layout.

Assisted-by: Claude:claude-opus-4-7
Co-developed-by: Adrien Ricciardi <[email protected]>
Signed-off-by: Adrien Ricciardi <[email protected]>
Signed-off-by: Drew Fustini <[email protected]>
---
 drivers/resctrl/cbqri_devices.c  | 85 ++++++++++++++++++++++++++++++++++++++++
 drivers/resctrl/cbqri_internal.h | 21 ++++++++++
 2 files changed, 106 insertions(+)

diff --git a/drivers/resctrl/cbqri_devices.c b/drivers/resctrl/cbqri_devices.c
index dc76a146e34d..e46b02d2c50d 100644
--- a/drivers/resctrl/cbqri_devices.c
+++ b/drivers/resctrl/cbqri_devices.c
@@ -105,6 +105,46 @@ static int cbqri_cc_alloc_op(struct cbqri_controller *ctrl, int operation,
 	return 0;
 }
 
+/*
+ * Issue a monitoring op on a CC or BC controller's mon_ctl register at
+ * reg_offset (CBQRI_CC_MON_CTL_OFF or CBQRI_BC_MON_CTL_OFF). The CC and
+ * BC mon_ctl registers share an identical OP/MCID/EVT_ID/STATUS layout, so
+ * one helper covers both. Caller must hold ctrl->lock.
+ */
+int cbqri_mon_op(struct cbqri_controller *ctrl, int reg_offset,
+		 int operation, int mcid, int evt_id, u64 *out_reg)
+{
+	u64 reg;
+
+	lockdep_assert_held(&ctrl->lock);
+
+	if (ctrl->faulted)
+		return -EIO;
+
+	if (cbqri_wait_busy_flag(ctrl, reg_offset, &reg) < 0) {
+		pr_err_ratelimited("BUSY timeout before starting operation\n");
+		return -EIO;
+	}
+	FIELD_MODIFY(CBQRI_MON_CTL_OP_MASK, &reg, operation);
+	FIELD_MODIFY(CBQRI_MON_CTL_MCID_MASK, &reg, mcid);
+	FIELD_MODIFY(CBQRI_MON_CTL_EVT_ID_MASK, &reg, evt_id);
+	iowrite64(reg, ctrl->base + reg_offset);
+
+	if (cbqri_wait_busy_flag(ctrl, reg_offset, &reg) < 0) {
+		pr_err_ratelimited("BUSY timeout\n");
+		return -EIO;
+	}
+
+	if (FIELD_GET(CBQRI_MON_CTL_STATUS_MASK, reg) !=
+	    CBQRI_MON_CTL_STATUS_SUCCESS)
+		return -EIO;
+
+	if (out_reg)
+		*out_reg = reg;
+
+	return 0;
+}
+
 /*
  * Apply a capacity block mask and verify via CONFIG_LIMIT + READ_LIMIT.
  *
@@ -310,6 +350,7 @@ static int cbqri_probe_feature(struct cbqri_controller *ctrl, int reg_offset,
 
 static int cbqri_probe_cc(struct cbqri_controller *ctrl)
 {
+	bool has_mon_at_code = false;
 	int err, status;
 	u64 reg;
 
@@ -361,6 +402,28 @@ static int cbqri_probe_cc(struct cbqri_controller *ctrl)
 	}
 	cpus_read_unlock();
 
+	/* Probe monitoring features */
+	err = cbqri_probe_feature(ctrl, CBQRI_CC_MON_CTL_OFF,
+				  CBQRI_CC_MON_CTL_OP_READ_COUNTER, &status,
+				  &has_mon_at_code);
+	if (err)
+		return err;
+
+	if (status == CBQRI_MON_CTL_STATUS_SUCCESS) {
+		/*
+		 * Occupancy is reported to userspace in bytes, computed as
+		 * cache_size * counter / ncblks by the resctrl glue. If
+		 * cacheinfo has no cache_size, leave mon_capable false so
+		 * the file is not exposed at all rather than silently
+		 * returning 0.
+		 */
+		if (!ctrl->cache.cache_size)
+			pr_debug("CC @%pa: cache_size unknown, occupancy monitoring disabled\n",
+				 &ctrl->addr);
+		else
+			ctrl->mon_capable = true;
+	}
+
 	/* Probe allocation features */
 	err = cbqri_probe_feature(ctrl, CBQRI_CC_ALLOC_CTL_OFF,
 				  CBQRI_CC_ALLOC_CTL_OP_READ_LIMIT,
@@ -428,6 +491,28 @@ static int cbqri_probe_controller(struct cbqri_controller *ctrl)
 	return err;
 }
 
+/*
+ * Pre-arm every MCID with the Occupancy event so a subsequent READ_COUNTER
+ * just snapshots the live counter rather than re-configuring the slot.
+ * Called once per CC during resctrl-side cpuhp online for the L3 monitoring
+ * domain.
+ */
+int cbqri_init_mon_counters(struct cbqri_controller *ctrl)
+{
+	int i, err;
+
+	for (i = 0; i < ctrl->mcid_count; i++) {
+		mutex_lock(&ctrl->lock);
+		err = cbqri_mon_op(ctrl, CBQRI_CC_MON_CTL_OFF,
+				   CBQRI_CC_MON_CTL_OP_CONFIG_EVENT,
+				   i, CBQRI_CC_EVT_ID_OCCUPANCY, NULL);
+		mutex_unlock(&ctrl->lock);
+		if (err)
+			return err;
+	}
+	return 0;
+}
+
 void cbqri_controller_destroy(struct cbqri_controller *ctrl)
 {
 	kfree(ctrl);
diff --git a/drivers/resctrl/cbqri_internal.h b/drivers/resctrl/cbqri_internal.h
index 6a581a7e417b..b1169ffc599f 100644
--- a/drivers/resctrl/cbqri_internal.h
+++ b/drivers/resctrl/cbqri_internal.h
@@ -11,6 +11,8 @@
 
 /* Capacity Controller (CC) MMIO register offsets. */
 #define CBQRI_CC_CAPABILITIES_OFF 0
+#define CBQRI_CC_MON_CTL_OFF      8
+#define CBQRI_CC_MON_CTL_VAL_OFF 16
 #define CBQRI_CC_ALLOC_CTL_OFF   24
 #define CBQRI_CC_BLOCK_MASK_OFF  32
 
@@ -39,6 +41,20 @@
 #define CBQRI_CC_ALLOC_CTL_OP_READ_LIMIT   2
 #define CBQRI_CC_ALLOC_CTL_STATUS_SUCCESS  1
 
+#define CBQRI_CC_MON_CTL_OP_CONFIG_EVENT 1
+#define CBQRI_CC_MON_CTL_OP_READ_COUNTER 2
+
+/* mon_ctl field masks (CC and BC share an identical OP/MCID/EVT_ID/STATUS layout) */
+#define CBQRI_MON_CTL_OP_MASK        GENMASK(4, 0)
+#define CBQRI_MON_CTL_MCID_MASK      GENMASK(19, 8)
+#define CBQRI_MON_CTL_EVT_ID_MASK    GENMASK(27, 20)
+#define CBQRI_MON_CTL_STATUS_MASK    GENMASK_ULL(38, 32)
+#define CBQRI_MON_CTL_STATUS_SUCCESS 1
+
+/* Capacity usage monitoring event IDs (CBQRI spec Table 4) */
+#define CBQRI_CC_EVT_ID_NONE         0
+#define CBQRI_CC_EVT_ID_OCCUPANCY    1
+
 /* Capacity Controller hardware capabilities */
 struct riscv_cbqri_capacity_caps {
 	u16 ncblks;
@@ -122,4 +138,9 @@ int cbqri_apply_cache_config(struct cbqri_controller *ctrl, u32 closid,
 int cbqri_read_cache_config(struct cbqri_controller *ctrl, u32 closid,
 			    enum cbqri_at at, u32 *cbm_out);
 
+int cbqri_mon_op(struct cbqri_controller *ctrl, int reg_offset,
+		 int operation, int mcid, int evt_id, u64 *out_reg);
+
+int cbqri_init_mon_counters(struct cbqri_controller *ctrl);
+
 #endif /* _DRIVERS_RESCTRL_CBQRI_INTERNAL_H */

-- 
2.43.0