Re: [PATCH 6/6] clocksource: tile: convert to use clocksource_register_hz

Chris Metcalf
2011-06-01T16:18:19Z

On 6/1/2011 3:32 AM, John Stultz wrote:
> From: John Stultz <johnstul@us.ibm.com>
>
> Convert tile to use clocksource_register_hz.
>
> Untested. Help from maintainers would be appreciated.
>
> CC: Chris Metcalf <cmetcalf@tilera.com>

This patch boots up fine on tile. It provides a shift count of 31, with a
mult value in the billions. This does mean that clocksource_cyc2ns() will
only be able to give correct timer conversions for up to about 9 seconds.
Is this believed to be adequate for all the uses the cycle counter is put
to? I can run our normal regression tests, but I'd like to get a
high-level sanity check from the clocksource folks.

The original shift of 22 was put in by commit
749dc6f252b57d5cb9c1f4c1c4aafe4c92a28207 back in August.

> CC: Thomas Gleixner <tglx@linutronix.de>
> Signed-off-by: John Stultz <johnstul@us.ibm.com>
> ---
> arch/tile/kernel/time.c | 5 +----
> 1 files changed, 1 insertions(+), 4 deletions(-)
>
> diff --git a/arch/tile/kernel/time.c b/arch/tile/kernel/time.c
> index c4be58c..f6f50f2a 100644
> --- a/arch/tile/kernel/time.c
> +++ b/arch/tile/kernel/time.c
> @@ -78,7 +78,6 @@ static struct clocksource cycle_counter_cs = {
> .rating = 300,
> .read = clocksource_get_cycles,
> .mask = CLOCKSOURCE_MASK(64),
> - .shift = 22, /* typical value, e.g. x86 tsc uses this */
> .flags = CLOCK_SOURCE_IS_CONTINUOUS,
> };
>
> @@ -91,8 +90,6 @@ void __init setup_clock(void)
> cycles_per_sec = hv_sysconf(HV_SYSCONF_CPU_SPEED);
> sched_clock_mult =
> clocksource_hz2mult(cycles_per_sec, SCHED_CLOCK_SHIFT);
> - cycle_counter_cs.mult =
> - clocksource_hz2mult(cycles_per_sec, cycle_counter_cs.shift);
> }
>
> void __init calibrate_delay(void)
> @@ -107,7 +104,7 @@ void __init calibrate_delay(void)
> void __init time_init(void)
> {
> /* Initialize and register the clock source. */
> - clocksource_register(&cycle_counter_cs);
> + clocksource_register_hz(&cycle_counter_cs, cycles_per_sec);
>
> /* Start up the tile-timer interrupt source on the boot cpu. */
> setup_tile_timer();

--
Chris Metcalf, Tilera Corp.