[coreboot-gerrit] [XS] Change in coreboot[main]: libpayload/x86: Add x86-64 support to rdtsc()

[Subrata Banik (Code Review)]

Subrata Banik has uploaded this change for review. ( https://review.coreboot.org/c/coreboot/+/83414?usp=email )

Change subject: libpayload/x86: Add x86-64 support to rdtsc()
......................................................................

libpayload/x86: Add x86-64 support to rdtsc()

This patch adds support for x86-64 to the rdtsc() function,
allowing it to correctly read the Time Stamp Counter (TSC)
on both 32-bit and 64-bit x86 architectures.

BUG=b:242829490
TEST=Builds and boots on google/rex0 and google/rex64 systems and
manually verified correct TSC readings on x86-32 and x86-64 hardware.

Change-Id: I0afac3db2e82a245a37c2e5cf2302bf1dad62c01
Signed-off-by: Subrata Banik 
---
M payloads/libpayload/include/x86/arch/rdtsc.h
1 file changed, 9 insertions(+), 0 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/14/83414/1

diff --git a/payloads/libpayload/include/x86/arch/rdtsc.h b/payloads/libpayload/include/x86/arch/rdtsc.h
index 41ab24a..36be002 100644
--- a/payloads/libpayload/include/x86/arch/rdtsc.h
+++ b/payloads/libpayload/include/x86/arch/rdtsc.h
@@ -31,11 +31,20 @@

#include <stdint.h>

+#if CONFIG(LP_ARCH_X86_64)
+static u64 rdtsc(void)
+{
+	unsigned int lo, hi;
+	__asm__ __volatile__ ("rdtsc" : "=a" (lo), "=d" (hi));
+	return (u64)hi << 32 | lo;
+}
+#else
 static u64 rdtsc(void)
 {
    u64 val;
    __asm__ __volatile__ ("rdtsc" : "=A" (val));
    return val;
 }
+#endif

#endif