A bug is reported(https://bugzilla.redhat.com/show_bug.cgi?id=1227208)
that, after resuming from S3, CPU is working at a low speed.
After investigation, it is found that, BIOS has modified the value
of THERM_CONTROL register during S3, changes it from 0 to 0x10,
while the latter means CPU can only get 25% of the Duty Cycle,
and this caused the problem.
Simple scenario to reproduce:
1.Boot up system
2.Get MSR with address 0x19a, it should output 0
3.Put system into sleep, then wake up
4.Get MSR with address 0x19a, it should output 0(actual it outputs 0x10)
Although this is a BIOS issue, it would be more robust for linux to deal
with this situation. This patch fixes this issue by saving/restoring
THERM_CONTROL(now called CLOCK_MODULATION) register on suspend/resume.
Tested-by: Marcin Kaszewski <marcin.kaszew...@intel.com>
Signed-off-by: Chen Yu <yu.c.c...@intel.com>
---
arch/x86/include/asm/suspend_64.h | 1 +
arch/x86/power/cpu.c | 2 ++
2 files changed, 3 insertions(+)
diff --git a/arch/x86/include/asm/suspend_64.h
b/arch/x86/include/asm/suspend_64.h
index 7ebf0eb..b9f5591 100644
--- a/arch/x86/include/asm/suspend_64.h
+++ b/arch/x86/include/asm/suspend_64.h
@@ -25,6 +25,7 @@ struct saved_context {
u64 misc_enable;
bool misc_enable_saved;
unsigned long efer;
+ unsigned long clock_modulation;
u16 gdt_pad; /* Unused */
struct desc_ptr gdt_desc;
u16 idt_pad;
diff --git a/arch/x86/power/cpu.c b/arch/x86/power/cpu.c
index 9ab5279..f82577b 100644
--- a/arch/x86/power/cpu.c
+++ b/arch/x86/power/cpu.c
@@ -97,6 +97,7 @@ static void __save_processor_state(struct saved_context *ctxt)
mtrr_save_fixed_ranges(NULL);
rdmsrl(MSR_EFER, ctxt->efer);
+ rdmsrl(MSR_IA32_THERM_CONTROL, ctxt->clock_modulation);
#endif
/*
@@ -178,6 +179,7 @@ static void notrace __restore_processor_state(struct
saved_context *ctxt)
#else
/* CONFIG X86_64 */
wrmsrl(MSR_EFER, ctxt->efer);
+ wrmsrl(MSR_IA32_THERM_CONTROL, ctxt->clock_modulation);
write_cr8(ctxt->cr8);
__write_cr4(ctxt->cr4);
#endif
--
1.8.4.2
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