MIPS: csrc-sb1250: Implement read_sched_clock

Use sb1250 hpt 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/9488/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/kernel/csrc-sb1250.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>
@@ -53,6 +54,11 @@ struct clocksource bcm1250_clocksource = {
 	.flags	= CLOCK_SOURCE_IS_CONTINUOUS,
 };
 
+static u64 notrace sb1250_read_sched_clock(void)
+{
+	return sb1250_hpt_get_cycles();
+}
+
 void __init sb1250_clocksource_init(void)
 {
 	struct clocksource *cs = &bcm1250_clocksource;
@@ -69,4 +75,6 @@ void __init sb1250_clocksource_init(void)
 						 R_SCD_TIMER_CFG)));
 
 	clocksource_register_hz(cs, V_SCD_TIMER_FREQ);
+
+	sched_clock_register(sb1250_read_sched_clock, 23, V_SCD_TIMER_FREQ);
 }