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| author | David Engraf <david.engraf@sysgo.com> | 2017-01-11 14:50:59 +0100 |
|---|---|---|
| committer | Daniel Lezcano <daniel.lezcano@linaro.org> | 2017-02-07 20:58:30 +0100 |
| commit | 7b9f1d16e6d1268ed45d98b36c77f8920e7a209e (patch) | |
| tree | 3a7150bf92e557609672906774f7e1e32a87127b | |
| parent | 4750535bc94b86fde06b0e698d6bac738b020be4 (diff) | |
| download | blackbird-op-linux-7b9f1d16e6d1268ed45d98b36c77f8920e7a209e.tar.gz blackbird-op-linux-7b9f1d16e6d1268ed45d98b36c77f8920e7a209e.zip | |
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>
| -rw-r--r-- | drivers/clocksource/tcb_clksrc.c | 16 |
1 files changed, 15 insertions, 1 deletions
diff --git a/drivers/clocksource/tcb_clksrc.c b/drivers/clocksource/tcb_clksrc.c index d4ca9962a759..745844ee973e 100644 --- a/drivers/clocksource/tcb_clksrc.c +++ b/drivers/clocksource/tcb_clksrc.c @@ -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. |
