On Tue, 2006-08-08 at 15:47 +0200, Haavard Skinnemoen wrote:
> Define CONFIG_GENERIC_TIME and remove arch-specific versions of
> do_{get,set}timeofday(). Define and use a clocksource based on the
> AVR32 cycle counter.
>
> Also clean up asm/timex.h a bit, including defining CLOCK_TICK_RATE
> to a "good cheat value" borrowed from MIPS instead of the i8254 value
> used by "everyone" else, which is really quite pointless on AVR32.
>
> Signed-off-by: Haavard Skinnemoen <[email protected]>
> ---
> arch/avr32/Kconfig | 4 +
> arch/avr32/kernel/time.c | 172 +++++++++-------------------------------------
> include/asm-avr32/timex.h | 26 ++++--
> 3 files changed, 59 insertions(+), 143 deletions(-)
Can't argue w/ a diffstat like that :)
Glad to see the code is working for you!
Acked-by: John Stultz <[email protected]>
> @@ -286,22 +183,22 @@ void __init time_init(void)
> (unsigned long)sysreg_read(COUNT),
> (unsigned long)sysreg_read(COMPARE));
>
> - if (!avr32_hpt_frequency && boot_cpu_data.clk)
> - avr32_hpt_frequency = clk_get_rate(boot_cpu_data.clk);
> -
> - if (avr32_hpt_frequency) {
> - cycles_per_jiffy = (avr32_hpt_frequency + HZ / 2) / HZ;
> + count_hz = clk_get_rate(boot_cpu_data.clk);
> + shift = clocksource_avr32.shift;
> + mult = clocksource_hz2mult(count_hz, shift);
> + clocksource_avr32.mult = mult;
> +
> + printk("Cycle counter: mult=%lu, shift=%lu\n", mult, shift);
> +
> + {
> + u64 tmp;
> +
> + tmp = TICK_NSEC;
> + tmp <<= shift;
> + tmp += mult / 2;
> + do_div(tmp, mult);
>
> - /* 10^6 * 2^32 / avr32_hpt_frequency */
> - {
> - u64 tmp = 1000000ULL << 32;
> - do_div(tmp, avr32_hpt_frequency);
> - sll32_usecs_per_cycle = tmp;
> - }
> -
> - printk("Using %u.%03u MHz high precision timer.\n",
> - ((avr32_hpt_frequency + 500) / 1000) / 1000,
> - ((avr32_hpt_frequency + 500) / 1000) % 1000);
> + cycles_per_jiffy = tmp;
That looks redundant to the calculate_interval code in timer.c and
points to a need for a generic nanosecond to cycles interface. I'll put
that on my TODO list.
> +/*
> + * This is the frequency of the timer used for Linux's timer interrupt.
> + * The value should be defined as accurate as possible or under certain
> + * circumstances Linux timekeeping might become inaccurate or fail.
> + *
> + * For many system the exact clockrate of the timer isn't known but due to
> + * the way this value is used we can get away with a wrong value as long
> + * as this value is:
> + *
> + * - a multiple of HZ
> + * - a divisor of the actual rate
> + *
> + * 500000 is a good such cheat value.
> + *
> + * The obscure number 1193182 is the same as used by the original i8254
> + * time in legacy PC hardware; the chip is never found in AVR32 systems.
> + */
> +#define CLOCK_TICK_RATE 500000 /* Underlying HZ */
>
Hmm.. Hopefully the future NTP cleanup will remove the need for these
sorts of, uh.. tricks. :)
thanks
-john
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
