[PATCHv2 04/11] arm: arch_timer: standardise counter reading

[Mark Rutland]

On Fri, Jan 11, 2013 at 01:23:33PM +0000, Santosh Shilimkar wrote:
> On Wednesday 09 January 2013 09:37 PM, Mark Rutland wrote:
> > We're currently inconsistent with respect to our accesses to the
> > physical and virtual counters, mixing and matching the two.
> >
> > This patch introduces and uses a function for accessing the correct
> > counter based on whether we're using physical or virtual interrupts.
> > All current accesses to the counter accessors are redirected through
> > it.
> >
> > Signed-off-by: Mark Rutland <mark.rutland at arm.com>
> > Acked-by: Catalin Marinas <catalin.marinas at arm.com>
> > Acked-by: Marc Zyngier <marc.zyngier at arm.com>
> > ---
> >   arch/arm/kernel/arch_timer.c |   48 ++++++++++-------------------------------
> >   1 files changed, 12 insertions(+), 36 deletions(-)
> >
> > diff --git a/arch/arm/kernel/arch_timer.c b/arch/arm/kernel/arch_timer.c
> > index 498c29f..0d2681c 100644
> > --- a/arch/arm/kernel/arch_timer.c
> > +++ b/arch/arm/kernel/arch_timer.c
> > @@ -272,51 +272,32 @@ static int arch_timer_available(void)
> >   	return 0;
> >   }
> >
> > -static u32 notrace arch_counter_get_cntpct32(void)
> > +u64 arch_timer_read_counter(void)
> >   {
> > -	cycle_t cnt = arch_counter_get_cntpct();
> > -
> > -	/*
> > -	 * The sched_clock infrastructure only knows about counters
> > -	 * with at most 32bits. Forget about the upper 24 bits for the
> > -	 * time being...
> > -	 */
> > -	return (u32)cnt;
> > +	if (arch_timer_use_virtual)
> > +		return arch_counter_get_cntvct();
> > +	else
> > +		return arch_counter_get_cntpct();
> >   }
> >
> 
> [...]
> 
> > @@ -489,18 +470,13 @@ int __init arch_timer_of_register(void)
> >
> >   int __init arch_timer_sched_clock_init(void)
> >   {
> > -	u32 (*cnt32)(void);
> >   	int err;
> >
> >   	err = arch_timer_available();
> >   	if (err)
> >   		return err;
> >
> > -	if (arch_timer_use_virtual)
> > -		cnt32 = arch_counter_get_cntvct32;
> > -	else
> > -		cnt32 = arch_counter_get_cntpct32;
> > -
> > -	setup_sched_clock(cnt32, 32, arch_timer_rate);
> > +	setup_sched_clock(arch_timer_read_counter32,
> > +			  32, arch_timer_rate);
> >   	return 0;
> >   }
> >
> I think the original idea had merit since the check was needed
> in init code instead of proposed one which has if check for
> every counter read function. No ?
> 

The original idea was good in that it avoided the check on each read path, but
in several places the logic got duplicated (e.g. for choosing which
width-altering wrapper in the above block). I'd like ensure this logic is
consolidated.

I'll change arch_timer_read_counter to a function pointer, and set this in
arch_timer_of_register before registering anything. Everything would still be
indirected through it, but it won't have to do a check on every read.

Thanks,
Mark.