[Intel-wired-lan] [PATCH v10 iwl-next 06/11] idpf: add mailbox access to read PTP clock time

[Olech, Milena]

On 4/8/2025 11:17 PM, Jacob Keller wrote:

>On 4/8/2025 3:30 AM, Milena Olech wrote:
>> +static int idpf_ptp_read_src_clk_reg_mailbox(struct idpf_adapter *adapter,
>> +					     struct ptp_system_timestamp *sts,
>> +					     u64 *src_clk)
>> +{
>> +	struct idpf_ptp_dev_timers clk_time;
>> +	int err;
>> +
>> +	/* Read the system timestamp pre PHC read */
>> +	ptp_read_system_prets(sts);
>> +
>> +	err = idpf_ptp_get_dev_clk_time(adapter, &clk_time);
>> +	if (err)
>> +		return err;
>> +
>> +	/* Read the system timestamp post PHC read */
>> +	ptp_read_system_postts(sts);
>> +
>> +	*src_clk = clk_time.dev_clk_time_ns;
>> +
>> +	return 0;
>> +}
>Not an objection, since its obvious using the direct register access is
>preferable when it is available. This will result in a fair amount of
>jitter since mailbox timing is unlikely to be consistent. We also cannot
>have sts be filled in somehow by the host because it might not be
>operating on the same system clock.
>

You're 100% right, reading the time of the clock through mailbox is not
efficient. But as you mentioned, direct register access is definitely
preferable.

Thanks,
Milena