netdev - [PATCH v3] net: sh_eth: do not advertise Gigabit capabilities when not available

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Message-Id: <20171208153540.3323-1-thomas.petazzoni@free-electrons.com>
Date:   Fri,  8 Dec 2017 16:35:40 +0100
From:   Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>
To:     "David S. Miller" <davem@...emloft.net>,
        Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
        Niklas Söderlund 
        <niklas.soderlund+renesas@...natech.se>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Simon Horman <horms+renesas@...ge.net.au>
Cc:     netdev@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
        Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>
Subject: [PATCH v3] net: sh_eth: do not advertise Gigabit capabilities when not available

Not all variants of the sh_eth hardware have Gigabit
support. Unfortunately, the current driver doesn't tell the PHY about
the limited MAC capabilities. Due to this, if you have a Gigabit
capable PHY, the PHY will advertise its Gigabit capability and
establish a link at 1Gbit/s, even though the MAC doesn't support it.

In order to avoid this, we use the recently introduced
phy_set_max_speed() to tell the PHY to not advertise speed higher than
100 MBit/s.

Tested on a SH7786 platform, with a Gigabit PHY.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>
---
Changes since v2:
 - Drop goto construction used in the phy_set_max_speed() error
   handling, as it is not needed. Suggested by Sergei Shtylyov.

Changes since v1:
 - Use phy_set_max_speed(), as suggested by Sergei Shtylyov
   <sergei.shtylyov@...entembedded.com>.
---
 drivers/net/ethernet/renesas/sh_eth.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/net/ethernet/renesas/sh_eth.c b/drivers/net/ethernet/renesas/sh_eth.c
index db72d13cebb9..75323000c364 100644
--- a/drivers/net/ethernet/renesas/sh_eth.c
+++ b/drivers/net/ethernet/renesas/sh_eth.c
@@ -1892,6 +1892,16 @@ static int sh_eth_phy_init(struct net_device *ndev)
 		return PTR_ERR(phydev);
 	}
 
+	/* mask with MAC supported features */
+	if (mdp->cd->register_type != SH_ETH_REG_GIGABIT) {
+		int err = phy_set_max_speed(phydev, SPEED_100);
+		if (err) {
+			netdev_err(ndev, "failed to limit PHY to 100 Mbit/s\n");
+			phy_disconnect(phydev);
+			return err;
+		}
+	}
+
 	phy_attached_info(phydev);
 
 	return 0;
-- 
2.14.3