2023-06-21 19:26:38

by Pawel Dembicki

Subject: [PATCH net-next 6/6] net: dsa: vsc73xx: fix MTU configuration

Switch in MAXLEN register store maximum size of data frame.
MTU size is 18 bytes smaller than frame size.

Current settings causes problems with packet forwarding.
This patch fix MTU settings to proper values.

Fixes: fb77ffc6ec86 ("net: dsa: vsc73xx: make the MTU configurable")

Signed-off-by: Pawel Dembicki <[email protected]>
---
drivers/net/dsa/vitesse-vsc73xx-core.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/net/dsa/vitesse-vsc73xx-core.c b/drivers/net/dsa/vitesse-vsc73xx-core.c
index fcce47cf6da4..a806a263cf08 100644
--- a/drivers/net/dsa/vitesse-vsc73xx-core.c
+++ b/drivers/net/dsa/vitesse-vsc73xx-core.c
@@ -992,17 +992,18 @@ static int vsc73xx_change_mtu(struct dsa_switch *ds, int port, int new_mtu)
struct vsc73xx *vsc = ds->priv;

return vsc73xx_write(vsc, VSC73XX_BLOCK_MAC, port,
- VSC73XX_MAXLEN, new_mtu);
+ VSC73XX_MAXLEN, new_mtu + ETH_HLEN + ETH_FCS_LEN);
}

/* According to application not "VSC7398 Jumbo Frames" setting
- * up the MTU to 9.6 KB does not affect the performance on standard
+ * up the frame size to 9.6 KB does not affect the performance on standard
* frames. It is clear from the application note that
* "9.6 kilobytes" == 9600 bytes.
*/
static int vsc73xx_get_max_mtu(struct dsa_switch *ds, int port)
{
- return 9600;
+ /* max mtu = 9600 - ETH_HLEN - ETH_FCS_LEN */
+ return 9582;
}

static void vsc73xx_port_stp_state_set(struct dsa_switch *ds, int port,
--
2.34.1

2023-06-21 21:45:46

by Linus Walleij

Subject: Re: [PATCH net-next 6/6] net: dsa: vsc73xx: fix MTU configuration

On Wed, Jun 21, 2023 at 9:14 PM Pawel Dembicki <[email protected]> wrote:

> Switch in MAXLEN register store maximum size of data frame.
> MTU size is 18 bytes smaller than frame size.
>
> Current settings causes problems with packet forwarding.
> This patch fix MTU settings to proper values.
>
> Fixes: fb77ffc6ec86 ("net: dsa: vsc73xx: make the MTU configurable")
>
> Signed-off-by: Pawel Dembicki <[email protected]>

Ooops my bad. Thanks for finding this.
Reviewed-by: Linus Walleij <[email protected]>

Yours,
Linus Walleij

2023-06-22 07:52:19

by Simon Horman

Subject: Re: [PATCH net-next 6/6] net: dsa: vsc73xx: fix MTU configuration

On Wed, Jun 21, 2023 at 09:13:02PM +0200, Pawel Dembicki wrote:
> Switch in MAXLEN register store maximum size of data frame.
> MTU size is 18 bytes smaller than frame size.
>
> Current settings causes problems with packet forwarding.
> This patch fix MTU settings to proper values.
>
> Fixes: fb77ffc6ec86 ("net: dsa: vsc73xx: make the MTU configurable")
>
> Signed-off-by: Pawel Dembicki <[email protected]>

Hi Pawel,

one minor nit on this one: there should not be a blank line between the Fixes
and Signed-off-by lines.