[S390] Introduce get_clock_fast()
Add get_clock_fast() which uses the slightly faster stckf if available.
If stckf is not available fall back to stck, which has the same width.
Signed-off-by: Jan Glauber <jang@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/include/asm/timex.h b/arch/s390/include/asm/timex.h
index 88829a4..d610bef 100644
--- a/arch/s390/include/asm/timex.h
+++ b/arch/s390/include/asm/timex.h
@@ -86,6 +86,17 @@
asm volatile("stcke %0" : "=Q" (*clk) : : "cc");
}
+static inline unsigned long long get_clock_fast(void)
+{
+ unsigned long long clk;
+
+ if (test_facility(25))
+ asm volatile(".insn s,0xb27c0000,%0" : "=Q" (clk) : : "cc");
+ else
+ clk = get_clock();
+ return clk;
+}
+
static inline unsigned long long get_clock_xt(void)
{
unsigned char clk[16];