[PATCH net] net: stmmac: Fix race between stmmac_drv_probe and stmmac_open

From: Florian Fainelli
Date: Tue Dec 27 2016 - 21:29:40 EST


There is currently a small window during which the network device registered by
stmmac can be made visible, yet all resources, including and clock and MDIO bus
have not had a chance to be set up, this can lead to the following error to
occur:

[ 473.919358] stmmaceth 0000:01:00.0 (unnamed net_device) (uninitialized):
stmmac_dvr_probe: warning: cannot get CSR clock
[ 473.919382] stmmaceth 0000:01:00.0: no reset control found
[ 473.919412] stmmac - user ID: 0x10, Synopsys ID: 0x42
[ 473.919429] stmmaceth 0000:01:00.0: DMA HW capability register supported
[ 473.919436] stmmaceth 0000:01:00.0: RX Checksum Offload Engine supported
[ 473.919443] stmmaceth 0000:01:00.0: TX Checksum insertion supported
[ 473.919451] stmmaceth 0000:01:00.0 (unnamed net_device) (uninitialized):
Enable RX Mitigation via HW Watchdog Timer
[ 473.921395] libphy: PHY stmmac-1:00 not found
[ 473.921417] stmmaceth 0000:01:00.0 eth0: Could not attach to PHY
[ 473.921427] stmmaceth 0000:01:00.0 eth0: stmmac_open: Cannot attach to
PHY (error: -19)
[ 473.959710] libphy: stmmac: probed
[ 473.959724] stmmaceth 0000:01:00.0 eth0: PHY ID 01410cc2 at 0 IRQ POLL
(stmmac-1:00) active
[ 473.959728] stmmaceth 0000:01:00.0 eth0: PHY ID 01410cc2 at 1 IRQ POLL
(stmmac-1:01)
[ 473.959731] stmmaceth 0000:01:00.0 eth0: PHY ID 01410cc2 at 2 IRQ POLL
(stmmac-1:02)
[ 473.959734] stmmaceth 0000:01:00.0 eth0: PHY ID 01410cc2 at 3 IRQ POLL
(stmmac-1:03)

Fix this by making sure that register_netdev() is the last thing being done,
which guarantees that the clock and the MDIO bus are available.

Fixes: 4bfcbd7abce2 ("stmmac: Move the mdio_register/_unregister in probe/remove")
Reported-by: Kweh, Hock Leong <hock.leong.kweh@xxxxxxxxx>
Signed-off-by: Florian Fainelli <f.fainelli@xxxxxxxxx>
---
drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 16 ++++++----------
1 file changed, 6 insertions(+), 10 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index bb40382e205d..5910ea51f8f6 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -3339,13 +3339,6 @@ int stmmac_dvr_probe(struct device *device,

spin_lock_init(&priv->lock);

- ret = register_netdev(ndev);
- if (ret) {
- netdev_err(priv->dev, "%s: ERROR %i registering the device\n",
- __func__, ret);
- goto error_netdev_register;
- }
-
/* If a specific clk_csr value is passed from the platform
* this means that the CSR Clock Range selection cannot be
* changed at run-time and it is fixed. Viceversa the driver'll try to
@@ -3372,11 +3365,14 @@ int stmmac_dvr_probe(struct device *device,
}
}

- return 0;
+ ret = register_netdev(ndev);
+ if (ret)
+ netdev_err(priv->dev, "%s: ERROR %i registering the device\n",
+ __func__, ret);
+
+ return ret;

error_mdio_register:
- unregister_netdev(ndev);
-error_netdev_register:
netif_napi_del(&priv->napi);
error_hw_init:
clk_disable_unprepare(priv->pclk);
--
2.9.3