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Commit 7b9f1d16 authored by David Engraf's avatar David Engraf Committed by Daniel Lezcano
Browse files

clocksource/drivers/tcb_clksrc: Use 32 bit tcb as sched_clock 



On newer boards the TC can be read as single 32 bit value without locking.
Thus the clock can be used as reference for sched_clock which is much more
accurate than the jiffies implementation.

Tested on a Atmel SAMA5D2 board.

Signed-off-by: default avatarDavid Engraf <david.engraf@sysgo.com>
Acked-by: default avatarNicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: default avatarDaniel Lezcano <daniel.lezcano@linaro.org>
parent 4750535b

drivers/clocksource/tcb_clksrc.c

+15 −1
Original line number Diff line number Diff line
@@ -10,6 +10,7 @@ 
#include <linux/io.h>

#include <linux/platform_device.h>

#include <linux/atmel_tc.h>

#include <linux/sched_clock.h>





/*
@@ -56,11 +57,16 @@ static u64 tc_get_cycles(struct clocksource *cs) 
	return (upper << 16) | lower;

}



static u64 tc_get_cycles32(struct clocksource *cs)

static u32 tc_get_cv32(void)

{

	return __raw_readl(tcaddr + ATMEL_TC_REG(0, CV));

}



static u64 tc_get_cycles32(struct clocksource *cs)

{

	return tc_get_cv32();

}



static struct clocksource clksrc = {

	.name           = "tcb_clksrc",

	.rating         = 200,
@@ -69,6 +75,11 @@ static struct clocksource clksrc = { 
	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,

};



static u64 notrace tc_read_sched_clock(void)

{

	return tc_get_cv32();

}



#ifdef CONFIG_GENERIC_CLOCKEVENTS



struct tc_clkevt_device {
@@ -339,6 +350,9 @@ static int __init tcb_clksrc_init(void) 
		clksrc.read = tc_get_cycles32;

		/* setup ony channel 0 */

		tcb_setup_single_chan(tc, best_divisor_idx);



		/* register sched_clock on chips with single 32 bit counter */

		sched_clock_register(tc_read_sched_clock, 32, divided_rate);

	} else {

		/* tclib will give us three clocks no matter what the

		 * underlying platform supports.