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Subject[PATCH net] net: phy: Don't assume loopback is supported
Date
Some PHYs may not support loopback mode so we need to check if register
is read-only.

Fixes: f0f9b4ed2338 ("net: phy: Add phy loopback support in net phy framework")
Signed-off-by: Jose Abreu <joabreu@synopsys.com>
Cc: Andrew Lunn <andrew@lunn.ch>
Cc: Florian Fainelli <f.fainelli@gmail.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Joao Pinto <joao.pinto@synopsys.com>
---
drivers/net/phy/phy_device.c | 20 ++++++++++++++++++--
1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
index 49fdd1ee798e..a749639d98c3 100644
--- a/drivers/net/phy/phy_device.c
+++ b/drivers/net/phy/phy_device.c
@@ -1918,8 +1918,24 @@ EXPORT_SYMBOL(genphy_resume);

int genphy_loopback(struct phy_device *phydev, bool enable)
{
- return phy_modify(phydev, MII_BMCR, BMCR_LOOPBACK,
- enable ? BMCR_LOOPBACK : 0);
+ int ret;
+
+ ret = phy_modify(phydev, MII_BMCR, BMCR_LOOPBACK,
+ enable ? BMCR_LOOPBACK : 0);
+ if (ret < 0)
+ return ret;
+
+ ret = phy_read(phydev, MII_BMCR);
+ if (ret < 0)
+ return ret;
+
+ if (enable) {
+ if (ret & BMCR_LOOPBACK)
+ return 0;
+ return -EOPNOTSUPP;
+ }
+
+ return 0;
}
EXPORT_SYMBOL(genphy_loopback);

--
2.7.4
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