From 0db6820b10c3452764ab62173c3b75cefbf6c215 Mon Sep 17 00:00:00 2001 From: Stefan Reinauer Date: Tue, 7 Aug 2012 14:44:51 -0700 Subject: Synchronize rdtsc instructions The CPU can arbitrarily reorder calls to rdtsc, significantly reducing the precision of timing using the CPUs time stamp counter. Unfortunately the method of synchronizing rdtsc is different on AMD and Intel CPUs. There is a generic method, using the cpuid instruction, but that uses up a lot of registers, and is very slow. Hence, use the correct lfence/mfence instructions (for CPUs that we know support it) Change-Id: I17ecb48d283f38f23148c13159aceda704c64ea5 Signed-off-by: Stefan Reinauer Reviewed-on: http://review.coreboot.org/1422 Reviewed-by: Alexandru Gagniuc Tested-by: build bot (Jenkins) --- src/cpu/intel/model_6fx/Kconfig | 1 + 1 file changed, 1 insertion(+) (limited to 'src/cpu/intel/model_6fx') diff --git a/src/cpu/intel/model_6fx/Kconfig b/src/cpu/intel/model_6fx/Kconfig index 851685cb06..4517f17fa6 100644 --- a/src/cpu/intel/model_6fx/Kconfig +++ b/src/cpu/intel/model_6fx/Kconfig @@ -4,3 +4,4 @@ config CPU_INTEL_MODEL_6FX select SSE2 select UDELAY_LAPIC select AP_IN_SIPI_WAIT + select TSC_SYNC_MFENCE -- cgit v1.2.3