From: Ilkka Koskinen ilkka@os.amperecomputing.com
[ Upstream commit 50572064ec7109b00eef8880e905f55861c8b3de ]
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/ce4b1442135fe03d0de41859b04b268c88c854a3.170749857... Signed-off-by: Will Deacon will@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/perf/arm-cmn.c | 11 +++++++++++ 1 file changed, 11 insertions(+)
diff --git a/drivers/perf/arm-cmn.c b/drivers/perf/arm-cmn.c index 47e7c3206939f..899e4ed49905c 100644 --- a/drivers/perf/arm-cmn.c +++ b/drivers/perf/arm-cmn.c @@ -2178,6 +2178,17 @@ 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);