[PATCH V2] x86/perf/zhaoxin: Add stepping check for ZXC

[silviazhao]

Some of Nano series processors will lead GP when accessing
PMC fixed counter. Meanwhile, their hardware support for PMC
has not announced externally. So exclude Nano CPUs from ZXC
by checking stepping information. This is an unambiguous way
to differentiate between ZXC and Nano CPUs.

Following are Nano and ZXC FMS information:
Nano FMS: Family=6, Model=F, Stepping=[0-A][C-D]
ZXC FMS:  Family=6, Model=F, Stepping=E-F OR
          Family=6, Model=0x19, Stepping=0-3

Fixes: 3a4ac121c2ca ("x86/perf: Add hardware performance events support for Zhaoxin CPU.")
Reported-by: Arjan <8vvbbqzo567a@xxxxxxxxxxxxxxxxx>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=212389
Reported-by: Kevin Brace <kevinbrace@xxxxxxx>

Signed-off-by: silviazhao <silviazhao-oc@xxxxxxxxxxx>
---
v1 -> v2: Add some statements for Nano and ZXC FMS information.
---
 arch/x86/events/zhaoxin/core.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/arch/x86/events/zhaoxin/core.c b/arch/x86/events/zhaoxin/core.c
index 949d845c922b..3e9acdaeed1e 100644
--- a/arch/x86/events/zhaoxin/core.c
+++ b/arch/x86/events/zhaoxin/core.c
@@ -541,7 +541,13 @@ __init int zhaoxin_pmu_init(void)
 
 	switch (boot_cpu_data.x86) {
 	case 0x06:
-		if (boot_cpu_data.x86_model == 0x0f || boot_cpu_data.x86_model == 0x19) {
+		/*
+		 * Support Zhaoxin CPU from ZXC series, exclude Nano series through FMS.
+		 * Nano FMS: Family=6, Model=F, Stepping=[0-A][C-D]
+		 * ZXC FMS: Family=6, Model=F, Stepping=E-F OR Family=6, Model=0x19, Stepping=0-3
+		 */
+		if ((boot_cpu_data.x86_model == 0x0f && boot_cpu_data.x86_stepping >= 0x0e) ||
+			boot_cpu_data.x86_model == 0x19) {
 
 			x86_pmu.max_period = x86_pmu.cntval_mask >> 1;
 
-- 
2.17.1