net: dsa: b53: fix max MTU for BCM5325/BCM5365

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@gmail.com>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

diff --git a/drivers/net/dsa/b53/b53_common.c b/drivers/net/dsa/b53/b53_common.c
index 6fed3eb15ad9b257c6fc3da20ce91b5e7129884c..e8b20bfa8b83ea7ac643bd5d005e2983747bd478 100644 (file)
--- 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;
 }