netdev - Re: [PATCH net-next] net: phylink: Support disabling autonegotiation for PCS

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Date:   Wed, 30 Jun 2021 19:02:51 +0100
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     Robert Hancock <robert.hancock@...ian.com>
Cc:     andrew@...n.ch, hkallweit1@...il.com, davem@...emloft.net,
        kuba@...nel.org, netdev@...r.kernel.org
Subject: Re: [PATCH net-next] net: phylink: Support disabling autonegotiation
 for PCS

On Wed, Jun 30, 2021 at 11:49:27AM -0600, Robert Hancock wrote:
> The auto-negotiation state in the PCS as set by
> phylink_mii_c22_pcs_config was previously always enabled when the driver is
> configured for in-band autonegotiation, even if autonegotiation was
> disabled on the interface with ethtool. Update the code to set the
> BMCR_ANENABLE bit based on the interface's autonegotiation enabled
> state.
> 
> Update phylink_mii_c22_pcs_get_state to not check
> autonegotiation-related fields when autonegotiation is disabled.
> 
> Update phylink_mac_pcs_get_state to initialize the state based on the
> interface's configured speed, duplex and pause parameters rather than to
> unknown when autonegotiation is disabled, before calling the driver's
> pcs_get_state functions, as they are not likely to provide meaningful data
> for these fields when autonegotiation is disabled. In this case the
> driver is really just filling in the link state field.
> 
> Note that in cases where there is a downstream PHY connected, such as
> with SGMII and a copper PHY, the configuration set by ethtool is handled by
> phy_ethtool_ksettings_set and not propagated to the PCS. This is correct
> since SGMII or 1000Base-X autonegotiation with the PCS should normally
> still be used even if the copper side has disabled it.
> 
> Signed-off-by: Robert Hancock <robert.hancock@...ian.com>

I definitely want to think about this _before_ it gets applied to
net-next. It's a substantial change, not a "fix" or something simple.

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