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authorIlkka Koskinen <ilkka@os.amperecomputing.com>2024-02-09 18:11:09 +0100
committerWill Deacon <will@kernel.org>2024-02-09 18:14:04 +0100
commit50572064ec7109b00eef8880e905f55861c8b3de (patch)
treecc3040d753cabaddba4f6b0b5494eee5f2a9f8ce
parentarm64: jump_label: use constraints "Si" instead of "i" (diff)
downloadlinux-50572064ec7109b00eef8880e905f55861c8b3de.tar.xz
linux-50572064ec7109b00eef8880e905f55861c8b3de.zip
perf/arm-cmn: Workaround AmpereOneX errata AC04_MESH_1 (incorrect child count)
AmpereOneX mesh implementation has a bug in HN-P nodes that makes them report incorrect child count. The failing crosspoints report 8 children while they only have two. When the driver tries to access the inexistent child nodes, it believes it has reached an invalid node type and probing fails. The workaround is to ignore those incorrect child nodes and continue normally. Signed-off-by: Ilkka Koskinen <ilkka@os.amperecomputing.com> [ rm: rewrote simpler generalised version ] Tested-by: Ilkka Koskinen <ilkka@os.amperecomputing.com> Signed-off-by: Robin Murphy <robin.murphy@arm.com> Link: https://lore.kernel.org/r/ce4b1442135fe03d0de41859b04b268c88c854a3.1707498577.git.robin.murphy@arm.com Signed-off-by: Will Deacon <will@kernel.org>
-rw-r--r--drivers/perf/arm-cmn.c11
1 files changed, 11 insertions, 0 deletions
diff --git a/drivers/perf/arm-cmn.c b/drivers/perf/arm-cmn.c
index c584165b13ba..7e3aa7e2345f 100644
--- a/drivers/perf/arm-cmn.c
+++ b/drivers/perf/arm-cmn.c
@@ -2305,6 +2305,17 @@ static int arm_cmn_discover(struct arm_cmn *cmn, unsigned int rgn_offset)
dev_dbg(cmn->dev, "ignoring external node %llx\n", reg);
continue;
}
+ /*
+ * AmpereOneX erratum AC04_MESH_1 makes some XPs report a bogus
+ * child count larger than the number of valid child pointers.
+ * A child offset of 0 can only occur on CMN-600; otherwise it
+ * would imply the root node being its own grandchild, which
+ * we can safely dismiss in general.
+ */
+ if (reg == 0 && cmn->part != PART_CMN600) {
+ dev_dbg(cmn->dev, "bogus child pointer?\n");
+ continue;
+ }
arm_cmn_init_node_info(cmn, reg & CMN_CHILD_NODE_ADDR, dn);