As we don't specify the MTU in the driver, the framework
will fall back to 1500 bytes and this doesn't work very
well when we try to attach a DSA switch:
eth1: mtu greater than device maximum
ixp4xx_eth c800a000.ethernet eth1: error -22 setting
MTU to 1504 to include DSA overhead
After locating an out-of-tree patch in OpenWrt I found
suitable code to set the MTU on the interface and ported
it and updated it. Now the MTU gets set properly.
Reviewed-by: Jacob Keller <[email protected]>
Signed-off-by: Linus Walleij <[email protected]>
---
Changes in v3:
- Fix some coding style and initialization style.
- Collect Jacob's review tag.
- Link to v2: https://lore.kernel.org/r/[email protected]
Changes in v2:
- Don't just set min/max MTU: implement the interface for actually
changing it as well.
- Link to v1: https://lore.kernel.org/r/[email protected]
---
drivers/net/ethernet/xscale/ixp4xx_eth.c | 65 +++++++++++++++++++++++++++++++-
1 file changed, 64 insertions(+), 1 deletion(-)
diff --git a/drivers/net/ethernet/xscale/ixp4xx_eth.c b/drivers/net/ethernet/xscale/ixp4xx_eth.c
index 3b0c5f177447..910094ab553c 100644
--- a/drivers/net/ethernet/xscale/ixp4xx_eth.c
+++ b/drivers/net/ethernet/xscale/ixp4xx_eth.c
@@ -24,6 +24,7 @@
#include <linux/dma-mapping.h>
#include <linux/dmapool.h>
#include <linux/etherdevice.h>
+#include <linux/if_vlan.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/net_tstamp.h>
@@ -63,7 +64,15 @@
#define POOL_ALLOC_SIZE (sizeof(struct desc) * (RX_DESCS + TX_DESCS))
#define REGS_SIZE 0x1000
-#define MAX_MRU 1536 /* 0x600 */
+
+/* MRU is said to be 14320 in a code dump, the SW manual says that
+ * MRU/MTU is 16320 and includes VLAN and ethernet headers.
+ * See "IXP400 Software Programmer's Guide" section 10.3.2, page 161.
+ *
+ * FIXME: we have chosen the safe default (14320) but if you can test
+ * jumboframes, experiment with 16320 and see what happens!
+ */
+#define MAX_MRU (14320 - VLAN_ETH_HLEN)
#define RX_BUFF_SIZE ALIGN((NET_IP_ALIGN) + MAX_MRU, 4)
#define NAPI_WEIGHT 16
@@ -1182,6 +1191,54 @@ static void destroy_queues(struct port *port)
}
}
+static int ixp4xx_do_change_mtu(struct net_device *dev, int new_mtu)
+{
+ struct port *port = netdev_priv(dev);
+ struct npe *npe = port->npe;
+ int framesize, chunks;
+ struct msg msg = {};
+
+ /* adjust for ethernet headers */
+ framesize = new_mtu + VLAN_ETH_HLEN;
+ /* max rx/tx 64 byte chunks */
+ chunks = DIV_ROUND_UP(framesize, 64);
+
+ msg.cmd = NPE_SETMAXFRAMELENGTHS;
+ msg.eth_id = port->id;
+
+ /* Firmware wants to know buffer size in 64 byte chunks */
+ msg.byte2 = chunks << 8;
+ msg.byte3 = chunks << 8;
+
+ msg.byte4 = msg.byte6 = framesize >> 8;
+ msg.byte5 = msg.byte7 = framesize & 0xff;
+
+ if (npe_send_recv_message(npe, &msg, "ETH_SET_MAX_FRAME_LENGTH"))
+ return -EIO;
+ netdev_dbg(dev, "set MTU on NPE %s to %d bytes\n",
+ npe_name(npe), new_mtu);
+
+ return 0;
+}
+
+static int ixp4xx_eth_change_mtu(struct net_device *dev, int new_mtu)
+{
+ int ret;
+
+ /* MTU can only be changed when the interface is up. We also
+ * set the MTU from dev->mtu when opening the device.
+ */
+ if (dev->flags & IFF_UP) {
+ ret = ixp4xx_do_change_mtu(dev, new_mtu);
+ if (ret < 0)
+ return ret;
+ }
+
+ dev->mtu = new_mtu;
+
+ return 0;
+}
+
static int eth_open(struct net_device *dev)
{
struct port *port = netdev_priv(dev);
@@ -1232,6 +1289,8 @@ static int eth_open(struct net_device *dev)
if (npe_send_recv_message(port->npe, &msg, "ETH_SET_FIREWALL_MODE"))
return -EIO;
+ ixp4xx_do_change_mtu(dev, dev->mtu);
+
if ((err = request_queues(port)) != 0)
return err;
@@ -1374,6 +1433,7 @@ static int eth_close(struct net_device *dev)
static const struct net_device_ops ixp4xx_netdev_ops = {
.ndo_open = eth_open,
.ndo_stop = eth_close,
+ .ndo_change_mtu = ixp4xx_eth_change_mtu,
.ndo_start_xmit = eth_xmit,
.ndo_set_rx_mode = eth_set_mcast_list,
.ndo_eth_ioctl = eth_ioctl,
@@ -1488,6 +1548,9 @@ static int ixp4xx_eth_probe(struct platform_device *pdev)
ndev->dev.dma_mask = dev->dma_mask;
ndev->dev.coherent_dma_mask = dev->coherent_dma_mask;
+ ndev->min_mtu = ETH_MIN_MTU;
+ ndev->max_mtu = MAX_MRU;
+
netif_napi_add_weight(ndev, &port->napi, eth_poll, NAPI_WEIGHT);
if (!(port->npe = npe_request(NPE_ID(port->id))))
---
base-commit: 0bb80ecc33a8fb5a682236443c1e740d5c917d1d
change-id: 20230923-ixp4xx-eth-mtu-c041d7efe932
Best regards,
--
Linus Walleij <[email protected]>
On 9/27/2023 3:12 PM, Linus Walleij wrote:
> As we don't specify the MTU in the driver, the framework
> will fall back to 1500 bytes and this doesn't work very
> well when we try to attach a DSA switch:
>
> eth1: mtu greater than device maximum
> ixp4xx_eth c800a000.ethernet eth1: error -22 setting
> MTU to 1504 to include DSA overhead
>
> After locating an out-of-tree patch in OpenWrt I found
> suitable code to set the MTU on the interface and ported
> it and updated it. Now the MTU gets set properly.
>
> Reviewed-by: Jacob Keller <[email protected]>
> Signed-off-by: Linus Walleij <[email protected]>
> ---
> Changes in v3:
> - Fix some coding style and initialization style.
> - Collect Jacob's review tag.
> - Link to v2: https://lore.kernel.org/r/[email protected]
>
Thanks for the cleanups! Looks good to me still.
-Jake