MIPS: csrc-bcm1480: Implement read_sched_clock

Use the ZBbus cycle counter for sched_clock source. This implementation
will give high resolution cputime accounting.
Signed-off-by: Deng-Cheng Zhu <dengcheng.zhu@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: macro@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/9480/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/kernel/csrc-bcm1480.c

@@ -12,6 +12,7 @@
  * GNU General Public License for more details.
  */
 #include <linux/clocksource.h>
+#include <linux/sched_clock.h>
 
 #include <asm/addrspace.h>
 #include <asm/io.h>
@@ -37,6 +38,11 @@ struct clocksource bcm1480_clocksource = {
 	.flags	= CLOCK_SOURCE_IS_CONTINUOUS,
 };
 
+static u64 notrace sb1480_read_sched_clock(void)
+{
+	return __raw_readq(IOADDR(A_SCD_ZBBUS_CYCLE_COUNT));
+}
+
 void __init sb1480_clocksource_init(void)
 {
 	struct clocksource *cs = &bcm1480_clocksource;
@@ -46,4 +52,6 @@ void __init sb1480_clocksource_init(void)
 	plldiv = G_BCM1480_SYS_PLL_DIV(__raw_readq(IOADDR(A_SCD_SYSTEM_CFG)));
 	zbbus = ((plldiv >> 1) * 50000000) + ((plldiv & 1) * 25000000);
 	clocksource_register_hz(cs, zbbus);
+
+	sched_clock_register(sb1480_read_sched_clock, 64, zbbus);
 }