Re: [PATCH v20 08/17] clocksource/drivers/arm_arch_timer: Rework counter frequency detection.

[Fu Wei]

Hi Hanjun,

On 19 January 2017 at 16:02, Hanjun Guo <hanjun.guo@xxxxxxxxxx> wrote:
> Hi Fuwei,
>
> One comments below.
>
>
> On 2017/1/18 21:25, fu.wei@xxxxxxxxxx wrote:
>>
>> From: Fu Wei <fu.wei@xxxxxxxxxx>
>>
>> The counter frequency detection call(arch_timer_detect_rate) combines two
>> ways to get counter frequency: system coprocessor register and MMIO timer.
>> But in a specific timer init code, we only need one way to try:
>> getting frequency from MMIO timer register will be needed only when we
>> init MMIO timer; getting frequency from system coprocessor register will
>> be needed only when we init arch timer.
>>
>> This patch separates paths to determine frequency:
>> Separate out the MMIO frequency and the sysreg frequency detection call,
>> and use the appropriate one for the counter.
>>
>> Signed-off-by: Fu Wei <fu.wei@xxxxxxxxxx>
>> ---
>>  drivers/clocksource/arm_arch_timer.c | 40
>> ++++++++++++++++++++++--------------
>>  1 file changed, 25 insertions(+), 15 deletions(-)
>>
>> diff --git a/drivers/clocksource/arm_arch_timer.c
>> b/drivers/clocksource/arm_arch_timer.c
>> index 6484f84..9482481 100644
>> --- a/drivers/clocksource/arm_arch_timer.c
>> +++ b/drivers/clocksource/arm_arch_timer.c
>> @@ -488,23 +488,33 @@ static int arch_timer_starting_cpu(unsigned int cpu)
>>         return 0;
>>  }
>>
>> -static void arch_timer_detect_rate(void __iomem *cntbase)
>> +static void __arch_timer_determine_rate(u32 rate)
>>  {
>> -       /* Who has more than one independent system counter? */
>> -       if (arch_timer_rate)
>> -               return;
>> +       /* Check the timer frequency. */
>> +       if (!arch_timer_rate) {
>> +               if (rate)
>> +                       arch_timer_rate = rate;
>> +               else
>> +                       pr_warn("frequency not available\n");
>> +       } else if (rate && arch_timer_rate != rate) {
>
>                         ^
> Typo? I think it's "&" here.

Not a typo, It's definitely a â&&â  :-)

Here arch_timer_rate is not zero.

If rate is not zero(that means we got a valid rate), and
arch_timer_rate != rate ,
we will print warning message.

>
> Thanks
> Hanjun



-- 
Best regards,

Fu Wei
Software Engineer
Red Hat