x86/perf/zhaoxin: Add stepping check for ZXC

[ Upstream commit fd636b6a9b ]

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: 3a4ac121c2 ("x86/perf: Add hardware performance events support for Zhaoxin CPU.")

Reported-by: Arjan <8vvbbqzo567a@nospam.xutrox.com>
Reported-by: Kevin Brace <kevinbrace@gmx.com>
Signed-off-by: silviazhao <silviazhao-oc@zhaoxin.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=212389
Signed-off-by: Sasha Levin <sashal@kernel.org>

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;