[PATCH 2/2] ARM: move IOP to use common mult/shift calculation code

[Mikael Pettersson]

Linus Walleij writes:
 > Since the infrastructure for determining shift/mult values from a
 > clock rate and a minimum programmable rate is now in the kernel,
 > lets remove this custom code.
 > 
 > Cc: Mikael Pettersson <mikpe at it.uu.se>
 > Cc: Deepak Saxena <dsaxena at plexity.net>
 > Signed-off-by: Linus Walleij <linus.walleij at stericsson.com>
 > ---
 > Mikael: I cannot test this change, but I have compiled it against
 > iop33x_defconfig. You'd have to test it and Acked-by: it before
 > I do anything else with it. Try to think about what a minimum range
 > would be for the generic IOP platform...
 > ---
 >  arch/arm/plat-iop/time.c |   53 +++++++--------------------------------------
 >  1 files changed, 9 insertions(+), 44 deletions(-)

This patch is equivalent to the one I sent on Dec 29
"[PATCH] iop: use generic clock mult/shift compute functions",
which RMK acked and Dan Williams then wrote he would handle via
xscaleiop.git.  Then it ended up in a black hole somewhere.  I was
going to re-send it if it wasn't in .35-rc1, but you beat me to it.

I've been using this since mid-December, so:
Acked-by: Mikael Pettersson <mikpe at it.uu.se>

The value of IOP_MIN_RANGE is a compromise between possibly longer
idle periods and timekeeping accuracy.  The current value of 4s is
known to work and give the same mult/shift values as before the
clocksource/clockevents conversion.  As I can't get even close to 4s
idle intervals, I see little point changing this value right now.

(Plus it seems kernel/time/clocksource.c wants a 5s upper bound on
this anyway.)

/Mikael

 > 
 > diff --git a/arch/arm/plat-iop/time.c b/arch/arm/plat-iop/time.c
 > index 6c8a02a..85d3e55 100644
 > --- a/arch/arm/plat-iop/time.c
 > +++ b/arch/arm/plat-iop/time.c
 > @@ -29,6 +29,11 @@
 >  #include <mach/time.h>
 >  
 >  /*
 > + * Minimum clocksource/clockevent timer range in seconds
 > + */
 > +#define IOP_MIN_RANGE 4
 > +
 > +/*
 >   * IOP clocksource (free-running timer 1).
 >   */
 >  static cycle_t iop_clocksource_read(struct clocksource *unused)
 > @@ -44,27 +49,6 @@ static struct clocksource iop_clocksource = {
 >  	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
 >  };
 >  
 > -static void __init iop_clocksource_set_hz(struct clocksource *cs, unsigned int hz)
 > -{
 > -	u64 temp;
 > -	u32 shift;
 > -
 > -	/* Find shift and mult values for hz. */
 > -	shift = 32;
 > -	do {
 > -		temp = (u64) NSEC_PER_SEC << shift;
 > -		do_div(temp, hz);
 > -		if ((temp >> 32) == 0)
 > -			break;
 > -	} while (--shift != 0);
 > -
 > -	cs->shift = shift;
 > -	cs->mult = (u32) temp;
 > -
 > -	printk(KERN_INFO "clocksource: %s uses shift %u mult %#x\n",
 > -	       cs->name, cs->shift, cs->mult);
 > -}
 > -
 >  /*
 >   * IOP sched_clock() implementation via its clocksource.
 >   */
 > @@ -130,27 +114,6 @@ static struct clock_event_device iop_clockevent = {
 >  	.set_mode	= iop_set_mode,
 >  };
 >  
 > -static void __init iop_clockevent_set_hz(struct clock_event_device *ce, unsigned int hz)
 > -{
 > -	u64 temp;
 > -	u32 shift;
 > -
 > -	/* Find shift and mult values for hz. */
 > -	shift = 32;
 > -	do {
 > -		temp = (u64) hz << shift;
 > -		do_div(temp, NSEC_PER_SEC);
 > -		if ((temp >> 32) == 0)
 > -			break;
 > -	} while (--shift != 0);
 > -
 > -	ce->shift = shift;
 > -	ce->mult = (u32) temp;
 > -
 > -	printk(KERN_INFO "clockevent: %s uses shift %u mult %#lx\n",
 > -	       ce->name, ce->shift, ce->mult);
 > -}
 > -
 >  static irqreturn_t
 >  iop_timer_interrupt(int irq, void *dev_id)
 >  {
 > @@ -190,7 +153,8 @@ void __init iop_init_time(unsigned long tick_rate)
 >  	 */
 >  	write_tmr0(timer_ctl & ~IOP_TMR_EN);
 >  	setup_irq(IRQ_IOP_TIMER0, &iop_timer_irq);
 > -	iop_clockevent_set_hz(&iop_clockevent, tick_rate);
 > +	clockevents_calc_mult_shift(&iop_clockevent,
 > +				    tick_rate, IOP_MIN_RANGE);
 >  	iop_clockevent.max_delta_ns =
 >  		clockevent_delta2ns(0xfffffffe, &iop_clockevent);
 >  	iop_clockevent.min_delta_ns =
 > @@ -207,6 +171,7 @@ void __init iop_init_time(unsigned long tick_rate)
 >  	write_trr1(0xffffffff);
 >  	write_tcr1(0xffffffff);
 >  	write_tmr1(timer_ctl);
 > -	iop_clocksource_set_hz(&iop_clocksource, tick_rate);
 > +	clocksource_calc_mult_shift(&iop_clocksource, tick_rate,
 > +				    IOP_MIN_RANGE);
 >  	clocksource_register(&iop_clocksource);
 >  }
 > -- 
 > 1.6.3.3
 >