netdev - Re: [PATCH net-next v4 8/9] net: dsa: dsa_slave_phy_connect(): extend phy's flags with port specific phy flags

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Date:   Fri, 11 Jun 2021 16:26:33 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Vladimir Oltean <olteanv@...il.com>,
        Oleksij Rempel <o.rempel@...gutronix.de>
Cc:     Woojung Huh <woojung.huh@...rochip.com>,
        UNGLinuxDriver@...rochip.com, Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, kernel@...gutronix.de,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Russell King <linux@...linux.org.uk>,
        Michael Grzeschik <m.grzeschik@...gutronix.de>
Subject: Re: [PATCH net-next v4 8/9] net: dsa: dsa_slave_phy_connect(): extend
 phy's flags with port specific phy flags



On 6/11/2021 12:24 PM, Vladimir Oltean wrote:
> On Fri, Jun 11, 2021 at 09:15:26AM +0200, Oleksij Rempel wrote:
>> This patch extends the flags of the phy that's being connected with the
>> port specific flags of the switch port.
>>
>> This is needed to handle a port specific erratum of the KSZ8873 switch,
>> which is added in a later patch.
>>
>> Signed-off-by: Oleksij Rempel <o.rempel@...gutronix.de>
>> ---
> 
> What happens differently between having this patch and not having it?

The current get_phy_flags() is only processed when we connect to a PHY
via a designed phy-handle property via phylink_of_phy_connect((, but if
we fallback on the internal MDIO bus created by a switch and take the
dsa_slave_phy_connect() path then we would not be processing that flag
and using it at PHY connection time. Oleksij, your proposed patch fails
to check that dsa_switch_ops::get_phy_flags is actually non-NULL, how
about this approach instead where we only fetch the flags once, and we
deal with an option get_phy_flags callback too:

diff --git a/net/dsa/slave.c b/net/dsa/slave.c
index d4756b920108..ba7866ec946f 100644
--- a/net/dsa/slave.c
+++ b/net/dsa/slave.c
@@ -1749,7 +1749,7 @@ static void dsa_slave_phylink_fixed_state(struct
phylink_config *config,
 }

 /* slave device setup
*******************************************************/
-static int dsa_slave_phy_connect(struct net_device *slave_dev, int addr)
+static int dsa_slave_phy_connect(struct net_device *slave_dev, int
addr, u32 flags)
 {
        struct dsa_port *dp = dsa_slave_to_port(slave_dev);
        struct dsa_switch *ds = dp->ds;
@@ -1760,6 +1760,8 @@ static int dsa_slave_phy_connect(struct net_device
*slave_dev, int addr)
                return -ENODEV;
        }

+       slave_dev->phydev->dev_flags |= flags;
+
        return phylink_connect_phy(dp->pl, slave_dev->phydev);
 }

@@ -1804,7 +1806,7 @@ static int dsa_slave_phy_setup(struct net_device
*slave_dev)
                /* We could not connect to a designated PHY or SFP, so
try to
                 * use the switch internal MDIO bus instead
                 */
-               ret = dsa_slave_phy_connect(slave_dev, dp->index);
+               ret = dsa_slave_phy_connect(slave_dev, dp->index,
phy_flags);
                if (ret) {
                        netdev_err(slave_dev,
                                   "failed to connect to port %d: %d\n",
-- 
Florian