diff mbox series

[net,v3,1/4] net: ethernet: cortina: Fix MTU max setting

Message ID 20231107-gemini-largeframe-fix-v3-1-e3803c080b75@linaro.org
State New
Headers
Series Fix large frames in the Gemini ethernet driver |

Commit Message

Linus Walleij Nov. 7, 2023, 9:54 a.m. UTC 
  The RX max frame size is over 10000 for the Gemini ethernet,
but the TX max frame size is actually just 2047 (0x7ff after
checking the datasheet). Reflect this in what we offer to Linux,
cap the MTU at the TX max frame minus ethernet headers.

Use the BIT() macro for related bit flags so these TX settings
are consistent.

Fixes: 4d5ae32f5e1e ("net: ethernet: Add a driver for Gemini gigabit ethernet")
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
---
 drivers/net/ethernet/cortina/gemini.c | 7 ++++---
 drivers/net/ethernet/cortina/gemini.h | 2 +-
 2 files changed, 5 insertions(+), 4 deletions(-)

Comments

Vladimir Oltean Nov. 8, 2023, 2:26 p.m. UTC | #1 
On Tue, Nov 07, 2023 at 10:54:26AM +0100, Linus Walleij wrote:
> The RX max frame size is over 10000 for the Gemini ethernet,
> but the TX max frame size is actually just 2047 (0x7ff after
> checking the datasheet). Reflect this in what we offer to Linux,
> cap the MTU at the TX max frame minus ethernet headers.
> 
> Use the BIT() macro for related bit flags so these TX settings
> are consistent.

What does this second paragraph intend to say? The patch doesn't use the
BIT() macro.
Linus Walleij Nov. 8, 2023, 2:37 p.m. UTC | #2 
On Wed, Nov 8, 2023 at 3:26 PM Vladimir Oltean <olteanv@gmail.com> wrote:
> On Tue, Nov 07, 2023 at 10:54:26AM +0100, Linus Walleij wrote:

> > The RX max frame size is over 10000 for the Gemini ethernet,
> > but the TX max frame size is actually just 2047 (0x7ff after
> > checking the datasheet). Reflect this in what we offer to Linux,
> > cap the MTU at the TX max frame minus ethernet headers.
> >
> > Use the BIT() macro for related bit flags so these TX settings
> > are consistent.
>
> What does this second paragraph intend to say? The patch doesn't use the
> BIT() macro.

Ah it's a leftover from v1 where I did some unrelated cleanup using
BIT() but Andrew remarked on it so I dropped it.

Maybe this twoliner in the commit message can be deleted when
applying?

Yours,
Linus Walleij
Vladimir Oltean Nov. 8, 2023, 3:29 p.m. UTC | #3 
On Wed, Nov 08, 2023 at 03:37:28PM +0100, Linus Walleij wrote:
> On Wed, Nov 8, 2023 at 3:26 PM Vladimir Oltean <olteanv@gmail.com> wrote:
> > On Tue, Nov 07, 2023 at 10:54:26AM +0100, Linus Walleij wrote:
> 
> > > The RX max frame size is over 10000 for the Gemini ethernet,
> > > but the TX max frame size is actually just 2047 (0x7ff after
> > > checking the datasheet). Reflect this in what we offer to Linux,
> > > cap the MTU at the TX max frame minus ethernet headers.
> > >
> > > Use the BIT() macro for related bit flags so these TX settings
> > > are consistent.
> >
> > What does this second paragraph intend to say? The patch doesn't use the
> > BIT() macro.
> 
> Ah it's a leftover from v1 where I did some unrelated cleanup using
> BIT() but Andrew remarked on it so I dropped it.
> 
> Maybe this twoliner in the commit message can be deleted when
> applying?

I think it's better if you do it, there are some more minor fixups which
you could bundle up with a new series.
diff mbox series

Patch

diff --git a/drivers/net/ethernet/cortina/gemini.c b/drivers/net/ethernet/cortina/gemini.c
index 5423fe26b4ef..ed9701f8ad9a 100644
--- a/drivers/net/ethernet/cortina/gemini.c
+++ b/drivers/net/ethernet/cortina/gemini.c
@@ -2464,11 +2464,12 @@  static int gemini_ethernet_port_probe(struct platform_device *pdev)
 
 	netdev->hw_features = GMAC_OFFLOAD_FEATURES;
 	netdev->features |= GMAC_OFFLOAD_FEATURES | NETIF_F_GRO;
-	/* We can handle jumbo frames up to 10236 bytes so, let's accept
-	 * payloads of 10236 bytes minus VLAN and ethernet header
+	/* We can receive jumbo frames up to 10236 bytes but only
+	 * transmit 2047 bytes so, let's accept payloads of 2047
+	 * bytes minus VLAN and ethernet header
 	 */
 	netdev->min_mtu = ETH_MIN_MTU;
-	netdev->max_mtu = 10236 - VLAN_ETH_HLEN;
+	netdev->max_mtu = MTU_SIZE_BIT_MASK - VLAN_ETH_HLEN;
 
 	port->freeq_refill = 0;
 	netif_napi_add(netdev, &port->napi, gmac_napi_poll);
diff --git a/drivers/net/ethernet/cortina/gemini.h b/drivers/net/ethernet/cortina/gemini.h
index 9fdf77d5eb37..201b4efe2937 100644
--- a/drivers/net/ethernet/cortina/gemini.h
+++ b/drivers/net/ethernet/cortina/gemini.h
@@ -502,7 +502,7 @@  union gmac_txdesc_3 {
 #define SOF_BIT			0x80000000
 #define EOF_BIT			0x40000000
 #define EOFIE_BIT		BIT(29)
-#define MTU_SIZE_BIT_MASK	0x1fff
+#define MTU_SIZE_BIT_MASK	0x7ff /* Max MTU 2047 bytes */
 
 /* GMAC Tx Descriptor */
 struct gmac_txdesc {