Re: [Xen-devel] [PATCH 3/5] x86/time: streamline platform time init on plt_init()

[Joao Martins <joao.m.martins@xxxxxxxxxx>]

On 03/18/2016 08:32 PM, Andrew Cooper wrote:
> On 17/03/16 16:12, Joao Martins wrote:
>> And use to initialize platform time solely for clocksource=tsc,
>> as opposed to initializing platform overflow timer, which would
>> only fire in ~180 years (on 2.2 Ghz Broadwell processor).
>>
>> Signed-off-by: Joao Martins <joao.m.martins@xxxxxxxxxx>
> 
> Again, just style corrections.
> 
> Reviewed-by Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> 
I've fixed all these comments in v2, too. Thanks!

>> diff --git a/xen/arch/x86/time.c b/xen/arch/x86/time.c
>> index 1311c58..5af8902 100644
>> --- a/xen/arch/x86/time.c
>> +++ b/xen/arch/x86/time.c
>> @@ -434,6 +434,7 @@ uint64_t ns_to_acpi_pm_tick(uint64_t ns)
>>  /************************************************************
>>   * PLATFORM TIMER 4: TSC
>>   */
>> +static bool_t clocksource_is_tsc = 0;
> 
> No need to explicitly initialise to 0.
> 
>>  static u64 tsc_freq;
>>  static unsigned long tsc_max_warp;
>>  static void tsc_check_reliability(void);
>> @@ -466,7 +467,7 @@ static int __init init_tsctimer(struct 
>> platform_timesource *pts)
>>      }
>>  
>>      pts->frequency = tsc_freq;
>> -    return tsc_reliable;
>> +    return ( clocksource_is_tsc = tsc_reliable );
> 
> While this does work, please avoid mixing an assignment and a return.
> 
> Something like
> 
> pts->frequency = tsc_freq;
> clocksource_is_tsc = tsc_reliable;
> 
> return tsc_reliable;
> 
> is fine and easier logic to read.
> 
>> @@ -633,11 +648,22 @@ static void __init init_platform_timer(void)
>>  
>>      set_time_scale(&plt_scale, pts->frequency);
>>  
>> -    plt_overflow_period = scale_delta(
>> -        1ull << (pts->counter_bits-1), &plt_scale);
>> -    init_timer(&plt_overflow_timer, plt_overflow, NULL, 0);
>>      plt_src = *pts;
>> -    plt_overflow(NULL);
>> +
>> +    if ( clocksource_is_tsc )
>> +    {
>> +        plt_init();
>> +    }
>> +    else
>> +    {
>> +        plt_overflow_period = scale_delta(
>> +            1ull << (pts->counter_bits-1), &plt_scale);
> 
> As you are moving this codeblock, please fix the style to
> (pts->counter_bits - 1)
> 
> ~Andrew
> 

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