Re: [PATCH 04/27] asm-generic: add legacy I/O header files

Russell King
2009-05-01T12:37:40Z

On Fri, May 01, 2009 at 02:25:14PM +0200, Michal Simek wrote:
> Arnd Bergmann wrote:
> > On Friday 01 May 2009, Michal Simek wrote:
> >>> +/*
> >>> + * CLOCK_TICK_RATE is highly PC-specific and should not
> >>> + * be used in portable code. 1193182 is the value for the
> >>> + * original i8253 PIC.
> >>> + */
> >>> +#ifndef CLOCK_TICK_RATE
> >>> +#define CLOCK_TICK_RATE 1193182
> >>> +#endif
> >>
> >> Why is this in generic code?
> >
> > CLOCK_TICK_RATE is only used in a few places:
> >
> > drivers/char/vt_ioctl.c: arg = CLOCK_TICK_RATE / arg;
> > drivers/char/vt_ioctl.c: count = CLOCK_TICK_RATE / count;
> > drivers/clocksource/acpi_pm.c: ((CALIBRATE_LATCH * (PMTMR_TICKS_PER_SEC >> 10)) / (CLOCK_TICK_RATE>>10))
> > drivers/input/joystick/analog.c:#define DELTA(x,y) (cpu_has_tsc ? ((y) - (x)) : ((x) - (y) + ((x) < (y) ? CLOCK_TICK_RATE / HZ : 0
> > drivers/rtc/rtc-pxa.c:#define TIMER_FREQ CLOCK_TICK_RATE
> > drivers/serial/serial_ks8695.c: .uartclk = CLOCK_TICK_RATE * 16,
> > drivers/watchdog/davinci_wdt.c: timer_margin = (((u64)heartbeat * CLOCK_TICK_RATE) & 0xffffffff);
> > drivers/watchdog/davinci_wdt.c: timer_margin = (((u64)heartbeat * CLOCK_TICK_RATE) >> 32);
> > drivers/watchdog/ks8695_wdt.c: unsigned long tval = wdt_time * CLOCK_TICK_RATE;
> > include/linux/jiffies.h:#define LATCH ((CLOCK_TICK_RATE + HZ/2) / HZ) /* For divider */
> > include/linux/jiffies.h:#define ACTHZ (SH_DIV (CLOCK_TICK_RATE, LATCH, 8))
> > include/linux/timex.h: * Moved CLOCK_TICK_RATE, CLOCK_TICK_FACTOR and FINETUNE to asm/timex.h
> > sound/oss/pas2_pcm.c: foo = ((CLOCK_TICK_RATE / 2) + (arg / 2)) / arg;
> > sound/oss/pas2_pcm.c: arg = ((CLOCK_TICK_RATE / 2) + (foo / 2)) / foo;
> > sound/oss/pas2_pcm.c: foo = (CLOCK_TICK_RATE + (arg / 2)) / arg;
> > sound/oss/pas2_pcm.c: arg = (CLOCK_TICK_RATE + (foo / 2)) / foo;
> >
> > All of these are either PC-specific, or they don't actually care
> > about the specific value. Most architectures just use the
> > value from the IBM PC, so we might as well make that the generic
> > default.
>
> ok. Let's move out from arch to generic location.

That's only possible once the users have been fixed - otherwise the ARM
stuff listed above _will_ break.

--
Russell King
Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/