[PATCH] 82xx: FCC: Fixing a bug causing to FCC port lock-up

[PATCH] 82xx: FCC: Fixing a bug causing to FCC port lock-up

[Martin Roth]

The patch fixes FCC port lock-up, which occurs as a result of a bug
during underrun/collision handling. Within the tx_startup() function
in mac-fcc.c, the address of last BD is not calculated correctly.
As a result of wrong calculation of the last BD address, the next
transmitted BD may be set to an area out of the transmit BD ring.
This actually causes to port lock-up and it is not recoverable.

Signed-off-by: Martin Roth <martin.roth@motorolasolutions.com>
---
 drivers/net/ethernet/freescale/fs_enet/mac-fcc.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/freescale/fs_enet/mac-fcc.c b/drivers/net/ethernet/freescale/fs_enet/mac-fcc.c
index 08f5b91..52e0091 100644
--- a/drivers/net/ethernet/freescale/fs_enet/mac-fcc.c
+++ b/drivers/net/ethernet/freescale/fs_enet/mac-fcc.c
@@ -552,7 +552,7 @@ static void tx_restart(struct net_device *dev)
 	cbd_t __iomem *prev_bd;
 	cbd_t __iomem *last_tx_bd;
 
-	last_tx_bd = fep->tx_bd_base + (fpi->tx_ring * sizeof(cbd_t));
+	last_tx_bd = fep->tx_bd_base + ((fpi->tx_ring - 1) * sizeof(cbd_t));
 
 	/* get the current bd held in TBPTR  and scan back from this point */
 	recheck_bd = curr_tbptr = (cbd_t __iomem *)
-- 
1.7.9.5

Re: [PATCH] 82xx: FCC: Fixing a bug causing to FCC port lock-up

[David Miller]

From: Martin Roth <martin.roth@motorolasolutions.com>
Date: Tue, 15 Dec 2015 04:17:53 +0200

> The patch fixes FCC port lock-up, which occurs as a result of a bug
> during underrun/collision handling. Within the tx_startup() function
> in mac-fcc.c, the address of last BD is not calculated correctly.
> As a result of wrong calculation of the last BD address, the next
> transmitted BD may be set to an area out of the transmit BD ring.
> This actually causes to port lock-up and it is not recoverable.
> 
> Signed-off-by: Martin Roth <martin.roth@motorolasolutions.com>

Applied, thanks.