ar71xx: ag71xx: fix a race involving netdev registration

In particular, phy_connect before register_netdev. This is because
register_netdev runs the netdev notifiers, which can race with the rest of
the initialization in ag71xx_probe. In my case this manifested in two ways:

1) If ag71xx is compiled as a module and inserted after netifd has started,
   netifd is notified by register_netdev before the call to
   ag71xx_phy_connect. netifd tries to bring the interface up, which calls
   ag71xx_open, which in turn enters ag71xx_phy_start. This keys off
   ag->phy_dev (which is still NULL) and thinks this is a fixed-link board,
   and enters ag71xx_link_adjust. This looks at ag->speed which is not yet
   initialized and hits the BUG() in the switch (ag->speed) in
   ag71xx_link_adjust.

   This is the wrong code path for ag71xx_phy_start - my board has PHYs that
   need to be brought up with phy_start. Doing ag71xx_phy_connect before
   register_netdev ensures that ag->phy_dev is non-NULL before
   ag71xx_phy_start is ever called.

2) When ag71xx is built into the kernel, and netconsole is enabled, there
   is a gap in the initial burst of replayed printks right after the netdev
   comes up. My assumption is that netconsole is also triggered by a netdev
   notifier, and part of this printk burst happens before the call into
   ag71xx_phy_connect, so part of the burst is lost while the PHY comes up.
   This patch fixes the gap - all the printks before eth0 comes up are bursted
   in full when netconsole initializes.

ag71xx_phy_connect_xxx no longer runs with a registered netdev, so the
logging has been adjusted accordingly to avoid "unregistered net_device" or
"eth%d" messages in dmesg.

Signed-off-by: Catalin Patulea <cat@vv.carleton.ca>
Signed-off-by: Gabor Juhos <juhosg@openwrt.org>

SVN-Revision: 38689

1 files changed, 11 insertions, 13 deletions

diff --git a/target/linux/ar71xx/files/drivers/net/ethernet/atheros/ag71xx/ag71xx_main.c b/target/linux/ar71xx/files/drivers/net/ethernet/atheros/ag71xx/ag71xx_main.c
index fc6be0e001..f4d6735349 100644
--- a/target/linux/ar71xx/files/drivers/net/ethernet/atheros/ag71xx/ag71xx_main.c
+++ b/target/linux/ar71xx/files/drivers/net/ethernet/atheros/ag71xx/ag71xx_main.c
@@ -1178,16 +1178,6 @@ static int ag71xx_probe(struct platform_device *pdev)
 
 	netif_napi_add(dev, &ag->napi, ag71xx_poll, AG71XX_NAPI_WEIGHT);
 
-	err = register_netdev(dev);
-	if (err) {
-		dev_err(&pdev->dev, "unable to register net device\n");
-		goto err_free_desc;
-	}
-
-	pr_info("%s: Atheros AG71xx at 0x%08lx, irq %d, mode:%s\n",
-		dev->name, dev->base_addr, dev->irq,
-		ag71xx_get_phy_if_mode_name(pdata->phy_if_mode));
-
 	ag71xx_dump_regs(ag);
 
 	ag71xx_hw_init(ag);
@@ -1196,7 +1186,7 @@ static int ag71xx_probe(struct platform_device *pdev)
 
 	err = ag71xx_phy_connect(ag);
 	if (err)
-		goto err_unregister_netdev;
+		goto err_free_desc;
 
 	err = ag71xx_debugfs_init(ag);
 	if (err)
@@ -1204,12 +1194,20 @@ static int ag71xx_probe(struct platform_device *pdev)
 
 	platform_set_drvdata(pdev, dev);
 
+	err = register_netdev(dev);
+	if (err) {
+		dev_err(&pdev->dev, "unable to register net device\n");
+		goto err_phy_disconnect;
+	}
+
+	pr_info("%s: Atheros AG71xx at 0x%08lx, irq %d, mode:%s\n",
+		dev->name, dev->base_addr, dev->irq,
+		ag71xx_get_phy_if_mode_name(pdata->phy_if_mode));
+
 	return 0;
 
 err_phy_disconnect:
 	ag71xx_phy_disconnect(ag);
-err_unregister_netdev:
-	unregister_netdev(dev);
 err_free_desc:
 	dma_free_coherent(NULL, sizeof(struct ag71xx_desc), ag->stop_desc,
 			  ag->stop_desc_dma);