Re: [Linuxptp-devel] [PATCH v1] phc_ctl: Implement setting frequency from system time.

[Maciek M. <ma...@ma...>]

On 11/10/2023 7:02 AM, Richard Cochran wrote:
> On Wed, Sep 13, 2023 at 05:09:04PM +0000, Maciek Machnikowski wrote:
>> Implement auto mode for frequency setting. In this mode the tool
>> will measure the frequency difference between PHC and CLOCK_REALTIME
>> and apply the correction to the PHC to match the system clock.
> 
> ...
> 
>> +		/* Try sysoff first */
>> +		method = sysoff_probe(fd, N_SAMPLES);
>> +		if (method >= 0) {
>> +			if (sysoff_measure(fd, method, N_SAMPLES,
>> +					   &t1_sys_offset,
>> +					   &t1_sys_ts, &t1_delay)) {
>> +				return -1;
>> +			}
>> +
>> +			sleep(1);
> 
> This measurement interval is WAY too short.  The time stamp error will
> spoil the syntonization.

In my tests it worked fine, but I'd be more than happy to increase it -
would 5s be sufficient there?

Thanks,
Maciek

>  
>> +			if (sysoff_measure(fd, method, N_SAMPLES,
>> +					   &t2_sys_offset,
>> +					   &t2_sys_ts, &t2_delay)) {
>> +				return -1;
>> +		       }
>> +
>> +			sys_diff = t2_sys_ts - t1_sys_ts;
>> +			clk_diff = t2_sys_offset - t1_sys_offset;
>> +			ppb += (1e9 - ppb) * ((double)clk_diff / (double)sys_diff);
> 
> Thanks,
> Richard
> 
> 
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