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From:   Bartosz Golaszewski <brgl@bgdev.pl>
To:     Grygorii Strashko <grygorii.strashko@ti.com>,
        "David S . Miller" <davem@davemloft.net>,
        Florian Fainelli <f.fainelli@gmail.com>,
        Dan Carpenter <dan.carpenter@oracle.com>,
        Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org>,
        Rob Herring <robh@kernel.org>, Lukas Wunner <lukas@wunner.de>,
        Kevin Hilman <khilman@kernel.org>,
        David Lechner <david@lechnology.com>,
        Sekhar Nori <nsekhar@ti.com>
Cc:     linux-omap@vger.kernel.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        Bartosz Golaszewski <bgolaszewski@baylibre.com>,
        stable@vger.kernel.org
Subject: [PATCH] net: ethernet: fix suspend/resume in davinci_emac
Date:   Tue, 19 Jun 2018 14:44:00 +0200
Message-Id: <20180619124400.11878-1-brgl@bgdev.pl>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

From: Bartosz Golaszewski <bgolaszewski@baylibre.com>

This patch reverts commit 3243ff2a05ec ("net: ethernet: davinci_emac:
Deduplicate bus_find_device() by name matching") and adds a comment
which should stop anyone from reintroducing the same "fix" in the future.

We can't use bus_find_device_by_name() here because the device name is
not guaranteed to be 'davinci_mdio'. On some systems it can be
'davinci_mdio.0' so we need to use strncmp() against the first part of
the string to correctly match it.

Fixes: 3243ff2a05ec ("net: ethernet: davinci_emac: Deduplicate bus_find_device() by name matching")
Cc: stable@vger.kernel.org
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
---
 drivers/net/ethernet/ti/davinci_emac.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/ti/davinci_emac.c b/drivers/net/ethernet/ti/davinci_emac.c
index 06d7c9e4dcda..a1a6445b5a7e 100644
--- a/drivers/net/ethernet/ti/davinci_emac.c
+++ b/drivers/net/ethernet/ti/davinci_emac.c
@@ -1385,6 +1385,11 @@ static int emac_devioctl(struct net_device *ndev, struct ifreq *ifrq, int cmd)
 		return -EOPNOTSUPP;
 }
 
+static int match_first_device(struct device *dev, void *data)
+{
+	return !strncmp(dev_name(dev), "davinci_mdio", 12);
+}
+
 /**
  * emac_dev_open - EMAC device open
  * @ndev: The DaVinci EMAC network adapter
@@ -1484,8 +1489,14 @@ static int emac_dev_open(struct net_device *ndev)
 
 	/* use the first phy on the bus if pdata did not give us a phy id */
 	if (!phydev && !priv->phy_id) {
-		phy = bus_find_device_by_name(&mdio_bus_type, NULL,
-					      "davinci_mdio");
+		/* NOTE: we can't use bus_find_device_by_name() here because
+		 * the device name is not guaranteed to be 'davinci_mdio'. On
+		 * some systems it can be 'davinci_mdio.0' so we need to use
+		 * strncmp() against the first part of the string to correctly
+		 * match it.
+		 */
+		phy = bus_find_device(&mdio_bus_type, NULL, NULL,
+				      match_first_device);
 		if (phy) {
 			priv->phy_id = dev_name(phy);
 			if (!priv->phy_id || !*priv->phy_id)
-- 
2.17.1