[PATCH 3/5] net: dsa: b53: fix max MTU for BCM5325/BCM5365

From: Jonas Gorski
Date: Fri Oct 04 2024 - 04:48:16 EST


BCM5325/BCM5365 do not support jumbo frames, so we should not report a
jumbo frame mtu for them. But they do support so called "oversized"
frames up to 1536 bytes long by default, so report an appropriate MTU.

Fixes: 6ae5834b983a ("net: dsa: b53: add MTU configuration support")
Signed-off-by: Jonas Gorski <jonas.gorski@xxxxxxxxx>
---
drivers/net/dsa/b53/b53_common.c | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/drivers/net/dsa/b53/b53_common.c b/drivers/net/dsa/b53/b53_common.c
index 6fed3eb15ad9b257c6fc3da20ce91b5e7129884c..e8b20bfa8b83ea7ac643bd5d005e2983747bd478 100644
--- a/drivers/net/dsa/b53/b53_common.c
+++ b/drivers/net/dsa/b53/b53_common.c
@@ -225,6 +225,7 @@ static const struct b53_mib_desc b53_mibs_58xx[] = {

#define B53_MIBS_58XX_SIZE ARRAY_SIZE(b53_mibs_58xx)

+#define B53_MAX_MTU_25 (1536 - ETH_HLEN - VLAN_HLEN - ETH_FCS_LEN)
#define B53_MAX_MTU (9720 - ETH_HLEN - VLAN_HLEN - ETH_FCS_LEN)

static int b53_do_vlan_op(struct b53_device *dev, u8 op)
@@ -2270,6 +2271,11 @@ static int b53_change_mtu(struct dsa_switch *ds, int port, int mtu)

static int b53_get_max_mtu(struct dsa_switch *ds, int port)
{
+ struct b53_device *dev = ds->priv;
+
+ if (is5325(dev) || is5365(dev))
+ return B53_MAX_MTU_25;
+
return B53_MAX_MTU;
}


--
2.43.0