linux-kernel - Re: [PATCH net v2 0/3] net: phy: micrel: Remove latencies support lan8814

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Message-ID: <Ykb2yoXHib6l9gkT@lunn.ch>
Date:   Fri, 1 Apr 2022 14:57:46 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Horatiu Vultur <horatiu.vultur@...rochip.com>
Cc:     netdev@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, hkallweit1@...il.com,
        linux@...linux.org.uk, Divya.Koppera@...rochip.com,
        davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com,
        richardcochran@...il.com, UNGLinuxDriver@...rochip.com
Subject: Re: [PATCH net v2 0/3] net: phy: micrel: Remove latencies support
 lan8814

On Fri, Apr 01, 2022 at 01:05:19PM +0200, Horatiu Vultur wrote:
> Remove the latencies support both from the PHY driver and from the DT.
> The IP already has some default latencies values which can be used to get
> decent results. It has the following values(defined in ns):
> rx-1000mbit: 429
> tx-1000mbit: 201
> rx-100mbit:  2346
> tx-100mbit:  705

So one alternative option here is that ptp4l looks at

/sys/class/net/<ifname>/phydev/phy_id

to identify the PHY, listens to netlink messages to determine the link
speed and then applies the correction itself in user space. That gives
you a pretty generic solution, works for any existing PHY and pretty
much any existing kernel version.  And if you want board specific
values you can override them in the ptp4l configuration file.

       Andrew