From: Chen Yu <yu.c.c...@intel.com>
Currently we fetch the tsc radio by:
ratio = (lo >> 8) & 0x1f;
thus get bit8~bit12 of the MSR_PLATFORM_INFO, however according
to Intel 64 and IA-32 Architectures Software Developer Manual 35.5,
the ratio bit should be bit8~bit15, otherwise we might get incorrect
tsc ratio and cause system hang later(mdelay corrupted).
Fix this problem by masking 0xff instead.
Cc: 3.14+ <sta...@vger.kernel.org> # 3.14+
Signed-off-by: Chen Yu <yu.c.c...@intel.com>
---
arch/x86/kernel/tsc_msr.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/kernel/tsc_msr.c b/arch/x86/kernel/tsc_msr.c
index 92ae6ac..6aa0f4d 100644
--- a/arch/x86/kernel/tsc_msr.c
+++ b/arch/x86/kernel/tsc_msr.c
@@ -92,7 +92,7 @@ unsigned long try_msr_calibrate_tsc(void)
if (freq_desc_tables[cpu_index].msr_plat) {
rdmsr(MSR_PLATFORM_INFO, lo, hi);
- ratio = (lo >> 8) & 0x1f;
+ ratio = (lo >> 8) & 0xff;
} else {
rdmsr(MSR_IA32_PERF_STATUS, lo, hi);
ratio = (hi >> 8) & 0x1f;
--
2.7.4
