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 <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]
Patchwork: https://patchwork.linux-mips.org/patch/9488/
Signed-off-by: Ralf Baechle <[e-mail]>

arch/mips/kernel/csrc-sb1250.c

···
  * GNU General Public License for more details.
  */
 #include <linux/clocksource.h>
+#include <linux/sched_clock.h>
 
 #include <asm/addrspace.h>
 #include <asm/io.h>
···
 	.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;
···
 						 R_SCD_TIMER_CFG)));
 
 	clocksource_register_hz(cs, V_SCD_TIMER_FREQ);
+
+	sched_clock_register(sb1250_read_sched_clock, 23, V_SCD_TIMER_FREQ);
 }