Subject: Re: [net-next PATCH] octeontx2: Add PTP clock driver for Octeon PTM clock.

From: Vinicius Costa Gomes <[email-masked]>
Date: Mon, 29 Jan 2024 17:31:12 -0800

Sai Krishna Gajula <[email-masked]> writes:

>> -----Original Message-----
>> From: Vinicius Costa Gomes <[email-masked]>
>> Sent: Friday, January 26, 2024 5:41 AM
>> To: Sai Krishna Gajula <[email-masked]>;
>> [email-masked]; [email-masked]; [email-masked];
>> [email-masked]; [email-masked]; Sunil Kovvuri
>> Goutham <[email-masked]>; Geethasowjanya Akula
>> <[email-masked]>; Linu Cherian <[email-masked]>; Hariprasad
>> Kelam <[email-masked]>; Subbaraya Sundeep Bhatta
>> <[email-masked]>
>> Cc: Sai Krishna Gajula <[email-masked]>; Naveen Mamindlapalli
>> <[email-masked]>
>> Subject: Re: [net-next PATCH] octeontx2: Add PTP clock driver for
>> Octeon PTM clock.
>> 
>> Sai Krishna <[email-masked]> writes:
>> 
>> > The PCIe PTM(Precision time measurement) protocol provides precise
>> > coordination of events across multiple components like PCIe host
>> > clock, PCIe EP PHC local clocks of PCIe devices. This patch adds
>> > support for ptp clock based PTM clock. We can use this PTP device to
>> > sync the PTM time with CLOCK_REALTIME or other PTP PHC devices using
>> > phc2sys.
>> >
>> > Signed-off-by: Sai Krishna <[email-masked]>
>> > Signed-off-by: Naveen Mamindlapalli <[email-masked]>
>> > Signed-off-by: Sunil Kovvuri Goutham <[email-masked]>
>> > ---
>> 
>> I can see that the same device id (PCI_DEVID_OCTEONTX2_PTP) is used by a
>> ethernet driver.
>> 
>> That brings me a question: why expose a different PTP chardev? In other
>> words, why can't you just implement .getcrosststamp() for that ethernet
>> device?
>
> This driver runs on endpoint device and not on the host.
> getcrosststamp() needs ART time, frequency details in case of x86 host
> system. Our use case is to sync the host's PTP/PTM time to the
> endpoint device via PTM interface.

Ah! I see. This is for "the other side", cool :-)

Cheers,
-- 
Vinicius