linux-kernel - [PATCH v2 3/8] perf/arm-cmn: Ensure dtm

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Message-Id: <e771b358526a0d7fc06efee2c3a2fdc0c9f51d44.1725296395.git.robin.murphy@arm.com>
Date: Mon,  2 Sep 2024 18:51:59 +0100
From: Robin Murphy <robin.murphy@....com>
To: will@...nel.org
Cc: mark.rutland@....com,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	ilkka@...amperecomputing.com
Subject: [PATCH v2 3/8] perf/arm-cmn: Ensure dtm_idx is big enough

While CMN_MAX_DIMENSION was bumped to 12 for CMN-650, that only supports
up to a 10x10 mesh, so bumping dtm_idx to 256 bits at the time worked
out OK in practice. However CMN-700 did finally support up to 144 XPs,
and thus needs a worst-case 288 bits of dtm_idx for an aggregated XP
event on a maxed-out config. Oops.

Fixes: 23760a014417 ("perf/arm-cmn: Add CMN-700 support")
Signed-off-by: Robin Murphy <robin.murphy@....com>
---

v2: Make the calculation more explicit
---
 drivers/perf/arm-cmn.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/perf/arm-cmn.c b/drivers/perf/arm-cmn.c
index 4e2338afe669..48863b31ccfb 100644
--- a/drivers/perf/arm-cmn.c
+++ b/drivers/perf/arm-cmn.c
@@ -35,6 +35,9 @@
 #define CMN_MAX_XPS			(CMN_MAX_DIMENSION * CMN_MAX_DIMENSION)
 #define CMN_MAX_DTMS			(CMN_MAX_XPS + (CMN_MAX_DIMENSION - 1) * 4)
 
+/* Currently XPs are the node type we can have most of; others top out at 128 */
+#define CMN_MAX_NODES_PER_EVENT		CMN_MAX_XPS
+
 /* The CFG node has various info besides the discovery tree */
 #define CMN_CFGM_PERIPH_ID_01		0x0008
 #define CMN_CFGM_PID0_PART_0		GENMASK_ULL(7, 0)
@@ -564,7 +567,7 @@ static void arm_cmn_debugfs_init(struct arm_cmn *cmn, int id) {}
 
 struct arm_cmn_hw_event {
 	struct arm_cmn_node *dn;
-	u64 dtm_idx[4];
+	u64 dtm_idx[DIV_ROUND_UP(CMN_MAX_NODES_PER_EVENT * 2, 64)];
 	s8 dtc_idx[CMN_MAX_DTCS];
 	u8 num_dns;
 	u8 dtm_offset;
-- 
2.39.2.101.g768bb238c484.dirty