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

[Santosh Shilimkar]

On Tuesday 15 January 2013 03:55 PM, Mark Rutland wrote:
> 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.
>
Sounds good