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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: David Engraf <david.engraf@sysgo.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
hifive-unleashed-5.1
David Engraf 2017-01-11 14:50:59 +01:00 committed by Daniel Lezcano
parent 4750535bc9
commit 7b9f1d16e6
1 changed files with 15 additions and 1 deletions
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16
drivers/clocksource/tcb_clksrc.c
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@ -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.