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

Vinicius Costa Gomes
2024-01-30T01:31:22Z

Sai Krishna Gajula <saikrishnag@marvell.com> writes:

>> -----Original Message-----
>> From: Vinicius Costa Gomes <vinicius.gomes@intel.com>
>> Sent: Friday, January 26, 2024 5:41 AM
>> To: Sai Krishna Gajula <saikrishnag@marvell.com>;
>> richardcochran@gmail.com; davem@davemloft.net; kuba@kernel.org;
>> netdev@vger.kernel.org; linux-kernel@vger.kernel.org; Sunil Kovvuri
>> Goutham <sgoutham@marvell.com>; Geethasowjanya Akula
>> <gakula@marvell.com>; Linu Cherian <lcherian@marvell.com>; Hariprasad
>> Kelam <hkelam@marvell.com>; Subbaraya Sundeep Bhatta
>> <sbhatta@marvell.com>
>> Cc: Sai Krishna Gajula <saikrishnag@marvell.com>; Naveen Mamindlapalli
>> <naveenm@marvell.com>
>> Subject: Re: [net-next PATCH] octeontx2: Add PTP clock driver for
>> Octeon PTM clock.
>>
>> Sai Krishna <saikrishnag@marvell.com> 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 <saikrishnag@marvell.com>
>> > Signed-off-by: Naveen Mamindlapalli <naveenm@marvell.com>
>> > Signed-off-by: Sunil Kovvuri Goutham <sgoutham@marvell.com>
>> > ---
>>
>> 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