csrc-r4k suffers from SMP synchronization overhead.

Select HAVE_UNSTABLE_SCHED_CLOCK to workaround drift
between the CPUs on the system. HAVE_UNSTABLE_SCHED_CLOCK
requires cmpxchg64, so enable it for 64 bits only.

Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
---
v2: Depends on SMP as well
---
 arch/mips/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index f1aa1bf11166..656df5d4097d 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -1083,6 +1083,7 @@ config CSRC_IOASIC
 
 config CSRC_R4K
 	select CLOCKSOURCE_WATCHDOG if CPU_FREQ
+	select HAVE_UNSTABLE_SCHED_CLOCK if SMP && 64BIT
 	bool
 
 config CSRC_SB1250

-- 
2.43.0