[PATCH] net: stmmac: Fixed mtu channged by cache aligned

[PATCH] net: stmmac: Fixed mtu channged by cache aligned

[David Wu]

Since the original mtu is not used when the mtu is updated,
the mtu is aligned with cache, this will get an incorrect.
For example, if you want to configure the mtu to be 1500,
but mtu 1536 is configured in fact.

Fixed: eaf4fac478077 ("net: stmmac: Do not accept invalid MTU values")
Signed-off-by: David Wu <david.wu@rock-chips.com>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 5b1c12ff98c0..e8640123db76 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -4025,7 +4025,7 @@ static void stmmac_set_rx_mode(struct net_device *dev)
 static int stmmac_change_mtu(struct net_device *dev, int new_mtu)
 {
 	struct stmmac_priv *priv = netdev_priv(dev);
-	int txfifosz = priv->plat->tx_fifo_size;
+	int txfifosz = priv->plat->tx_fifo_size, mtu = new_mtu;
 
 	if (txfifosz == 0)
 		txfifosz = priv->dma_cap.tx_fifo_size;
@@ -4043,7 +4043,7 @@ static int stmmac_change_mtu(struct net_device *dev, int new_mtu)
 	if ((txfifosz < new_mtu) || (new_mtu > BUF_SIZE_16KiB))
 		return -EINVAL;
 
-	dev->mtu = new_mtu;
+	dev->mtu = mtu;
 
 	netdev_update_features(dev);
 
-- 
2.19.1

Re: [PATCH] net: stmmac: Fixed mtu channged by cache aligned

[Jakub Kicinski]

On Wed, 13 Jan 2021 11:41:09 +0800 David Wu wrote:
> Since the original mtu is not used when the mtu is updated,
> the mtu is aligned with cache, this will get an incorrect.
> For example, if you want to configure the mtu to be 1500,
> but mtu 1536 is configured in fact.
> 
> Fixed: eaf4fac478077 ("net: stmmac: Do not accept invalid MTU values")
> Signed-off-by: David Wu <david.wu@rock-chips.com>
> ---
>  drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> index 5b1c12ff98c0..e8640123db76 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> @@ -4025,7 +4025,7 @@ static void stmmac_set_rx_mode(struct net_device *dev)
>  static int stmmac_change_mtu(struct net_device *dev, int new_mtu)
>  {
>  	struct stmmac_priv *priv = netdev_priv(dev);
> -	int txfifosz = priv->plat->tx_fifo_size;
> +	int txfifosz = priv->plat->tx_fifo_size, mtu = new_mtu;

Adjusted the code a little here to keep the variable declaration lines
ordered longest to shortest, and applied. 

Thanks!