linux-kernel - RE: [PATCH v5 net-next 08/15] ptp: netc: add debugfs support to loop back pulse signal

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Message-ID:
 <PAXPR04MB85100D1DF289DE8BCCC8D2A18839A@PAXPR04MB8510.eurprd04.prod.outlook.com>
Date: Tue, 26 Aug 2025 05:40:26 +0000
From: Wei Fang <wei.fang@....com>
To: Andrew Lunn <andrew@...n.ch>, "richardcochran@...il.com"
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Subject: RE: [PATCH v5 net-next 08/15] ptp: netc: add debugfs support to loop
 back pulse signal

> On Tue, Aug 26, 2025 at 01:50:06AM +0000, Wei Fang wrote:
> > > On Mon, Aug 25, 2025 at 12:15:25PM +0800, Wei Fang wrote:
> > > > The NETC Timer supports to loop back the output pulse signal of Fiper-n
> > > > into Trigger-n input, so that we can leverage this feature to validate
> > > > some other features without external hardware support.
> > >
> > > This seems like it should be a common feature which more PTP clocks
> > > will support? Did you search around and see if there are other devices
> > > with this?
> >
> > Actually, the NETC v4 Timer is the same IP used in the QorIQ platforms,
> > but it is a different version, and the ptp_qoriq driver is not compatible
> > with NETC v4 Timer, I have stated in the patch ("ptp: netc: add NETC V4
> > Timer PTP driver support").
> 
> That does not answer my question. Does Marvell have this loopback
> concept? Intel? Freescale? Microchip? Is there anything which prevents
> other vendors implementing it?
> 

It's hard for me to answer the question, I don't have the RM of other vendors,
and I also searched the drivers, I did not find the similar implementations. As
far as I know, the NXP TJA11xx PHYs also support the loop back the PPS signal,
but this feature is not yet implemented in the driver.

This feature should be easy to implement for most vendors, but it is only used
for debugging. I could add a generic API to support this, perhaps through an
interface to sysfs-ptp.