netdev - Re: [PATCH net-next] net: ethtool: allow MAC drivers to override ethtool get_ts

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Date:   Thu, 14 Jan 2021 17:31:11 +0000
From:   Russell King - ARM Linux admin <linux@...linux.org.uk>
To:     Richard Cochran <richardcochran@...il.com>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org
Subject: Re: [PATCH net-next] net: ethtool: allow MAC drivers to override
 ethtool get_ts_info

On Thu, Jan 14, 2021 at 09:27:12AM -0800, Richard Cochran wrote:
> On Thu, Jan 14, 2021 at 01:32:35PM +0000, Russell King - ARM Linux admin wrote:
> > > We had already discussed this patch last year, and you agreed with it
> > > then. What has changed?
> > 
> > See the discussion in this sub-thread:
> > 
> > https://lore.kernel.org/netdev/20200729105807.GZ1551@shell.armlinux.org.uk/
> 
> Thanks for the reminder.  We ended up with having to review the MAC
> drivers that support phydev.
> 
>    https://lore.kernel.org/netdev/20200730194427.GE1551@shell.armlinux.org.uk/
> 
> There is at least the FEC that supports phydev.  I have a board that
> combines the FEC with the dp83640 PHYTER, and your patch would break
> this setup.  (In the case of this HW combination, the PHYTER is
> superior in every way.)
> 
> Another combination that I have seen twice is the TI am335x with its
> cpsw MAC and the PHYTER.  Unfortunately I don't have one of these
> boards, but people made them because the cpsw MAC supports time
> stamping in a way that is inadequate.
> 
> I *think* the cpsw/phyter combination would work with your patch, but
> only if the users disable CONFIG_TI_CPTS at compile time.

I think then the only solution is to move the decision how to handle
get_ts_info into each MAC driver and get rid of:

	if (phy_has_tsinfo(phydev))
	        return phy_ts_info(phydev, info);

in __ethtool_get_ts_info().

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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