[PATCH v3 2/2] perf/arm-cmn: Add workarounds for CMN-S3 on Graviton5

[Aviv Bakal]

Graviton5 uses a customised CMN-S3 implementation where certain
discovery registers report zeroed fields. Add the following workarounds:

 - Introduce a dedicated ACPI HID to identify the Graviton5 CMN variant.
 - Derive the DTC domain from the XP node ID, since the unit info
   register reports it as zero.
 - Set the DTC logical ID from the XP's logical ID, since the node info
   register's logical ID field is also zeroed.

Signed-off-by: Aviv Bakal <avivb at amazon.com>
---
 drivers/perf/arm-cmn.c | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/drivers/perf/arm-cmn.c b/drivers/perf/arm-cmn.c
index 3443b819afed..0184e598777a 100644
--- a/drivers/perf/arm-cmn.c
+++ b/drivers/perf/arm-cmn.c
@@ -208,6 +208,8 @@ enum cmn_part {
 	PART_CMN700 = 0x43c,
 	PART_CI700 = 0x43a,
 	PART_CMN_S3 = 0x43e,
+	/* Synthetic part number, overridden to PART_CMN_S3 during discovery */
+	PART_GRAVITON5 = 0xa5,
 };
 
 /* CMN-600 r0px shouldn't exist in silicon, thankfully */
@@ -2197,6 +2199,18 @@ static unsigned int arm_cmn_dtc_domain(struct arm_cmn *cmn, void __iomem *xp_reg
 	return FIELD_GET(CMN_DTM_UNIT_INFO_DTC_DOMAIN, readl_relaxed(xp_region + offset));
 }
 
+static unsigned int arm_cmn_graviton5_dtc_domain(u16 xp_id)
+{
+	unsigned int x = (xp_id >> 7) & 0xf;
+	unsigned int y = (xp_id >> 3) & 0xf;
+
+	/*
+	 * The unit info register reads as zero; derive the DTC domain from
+	 * the XP's mesh coordinates over the 10x14 mesh.
+	 */
+	return (x / 5) + (y / 7) * 2;
+}
+
 static void arm_cmn_init_node_info(struct arm_cmn *cmn, u32 offset, struct arm_cmn_node *node)
 {
 	int level;
@@ -2242,6 +2256,7 @@ static int arm_cmn_discover(struct arm_cmn *cmn, unsigned int rgn_offset)
 	u64 reg;
 	int i, j;
 	size_t sz;
+	bool graviton5_workaround = false;
 
 	arm_cmn_init_node_info(cmn, rgn_offset, &cfg);
 	if (cfg.type != CMN_TYPE_CFG)
@@ -2252,6 +2267,13 @@ static int arm_cmn_discover(struct arm_cmn *cmn, unsigned int rgn_offset)
 	reg = readq_relaxed(cfg_region + CMN_CFGM_PERIPH_ID_01);
 	part = FIELD_GET(CMN_CFGM_PID0_PART_0, reg);
 	part |= FIELD_GET(CMN_CFGM_PID1_PART_1, reg) << 8;
+
+	/* Graviton5 has a customised CMN-S3 which needs some fixups */
+	if (cmn->part == PART_GRAVITON5) {
+		cmn->part = PART_CMN_S3;
+		graviton5_workaround = true;
+	}
+
 	/* 600AE is close enough that it's not really worth more complexity */
 	if (part == PART_CMN600AE)
 		part = PART_CMN600;
@@ -2341,6 +2363,8 @@ static int arm_cmn_discover(struct arm_cmn *cmn, unsigned int rgn_offset)
 
 		if (cmn->part == PART_CMN600)
 			xp->dtc = -1;
+		else if (graviton5_workaround)
+			xp->dtc = arm_cmn_graviton5_dtc_domain(xp->id);
 		else
 			xp->dtc = arm_cmn_dtc_domain(cmn, xp_region);
 
@@ -2419,6 +2443,10 @@ static int arm_cmn_discover(struct arm_cmn *cmn, unsigned int rgn_offset)
 
 			switch (dn->type) {
 			case CMN_TYPE_DTC:
+				if (graviton5_workaround) {
+					/* Node info logical ID is zeroed; use the XP's */
+					dn->logid = xp->logid;
+				}
 				cmn->num_dtcs++;
 				dn++;
 				break;
@@ -2634,6 +2662,7 @@ static const struct acpi_device_id arm_cmn_acpi_match[] = {
 	{ "ARMHC650" },
 	{ "ARMHC700" },
 	{ "ARMHC003" },
+	{ "AMZN0070", PART_GRAVITON5 },
 	{}
 };
 MODULE_DEVICE_TABLE(acpi, arm_cmn_acpi_match);
-- 
2.47.3