net: dsa: rtl8366rb: Support setting MTU

This implements the missing MTU setting for the RTL8366RB
switch.

Apart from supporting jumboframes, this rids us of annoying
boot messages like this:
realtek-smi switch: nonfatal error -95 setting MTU on port 0

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/net/dsa/rtl8366rb.c b/drivers/net/dsa/rtl8366rb.c
index 48f1ff7..f763f93 100644 (file)
--- a/drivers/net/dsa/rtl8366rb.c
+++ b/drivers/net/dsa/rtl8366rb.c
@@ -35,7 +35,7 @@
 #define RTL8366RB_SGCR_MAX_LENGTH_1522         RTL8366RB_SGCR_MAX_LENGTH(0x0)
 #define RTL8366RB_SGCR_MAX_LENGTH_1536         RTL8366RB_SGCR_MAX_LENGTH(0x1)
 #define RTL8366RB_SGCR_MAX_LENGTH_1552         RTL8366RB_SGCR_MAX_LENGTH(0x2)
-#define RTL8366RB_SGCR_MAX_LENGTH_9216         RTL8366RB_SGCR_MAX_LENGTH(0x3)
+#define RTL8366RB_SGCR_MAX_LENGTH_16000                RTL8366RB_SGCR_MAX_LENGTH(0x3)
 #define RTL8366RB_SGCR_EN_VLAN                 BIT(13)
 #define RTL8366RB_SGCR_EN_VLAN_4KTB            BIT(14)
 
@@ -1077,6 +1077,40 @@ rtl8366rb_port_disable(struct dsa_switch *ds, int port)
        rb8366rb_set_port_led(smi, port, false);
 }
 
+static int rtl8366rb_change_mtu(struct dsa_switch *ds, int port, int new_mtu)
+{
+       struct realtek_smi *smi = ds->priv;
+       u32 len;
+
+       /* The first setting, 1522 bytes, is max IP packet 1500 bytes,
+        * plus ethernet header, 1518 bytes, plus CPU tag, 4 bytes.
+        * This function should consider the parameter an SDU, so the
+        * MTU passed for this setting is 1518 bytes. The same logic
+        * of subtracting the DSA tag of 4 bytes apply to the other
+        * settings.
+        */
+       if (new_mtu <= 1518)
+               len = RTL8366RB_SGCR_MAX_LENGTH_1522;
+       else if (new_mtu > 1518 && new_mtu <= 1532)
+               len = RTL8366RB_SGCR_MAX_LENGTH_1536;
+       else if (new_mtu > 1532 && new_mtu <= 1548)
+               len = RTL8366RB_SGCR_MAX_LENGTH_1552;
+       else
+               len = RTL8366RB_SGCR_MAX_LENGTH_16000;
+
+       return regmap_update_bits(smi->map, RTL8366RB_SGCR,
+                                 RTL8366RB_SGCR_MAX_LENGTH_MASK,
+                                 len);
+}
+
+static int rtl8366rb_max_mtu(struct dsa_switch *ds, int port)
+{
+       /* The max MTU is 16000 bytes, so we subtract the CPU tag
+        * and the max presented to the system is 15996 bytes.
+        */
+       return 15996;
+}
+
 static int rtl8366rb_get_vlan_4k(struct realtek_smi *smi, u32 vid,
                                 struct rtl8366_vlan_4k *vlan4k)
 {
@@ -1415,6 +1449,8 @@ static const struct dsa_switch_ops rtl8366rb_switch_ops = {
        .port_vlan_del = rtl8366_vlan_del,
        .port_enable = rtl8366rb_port_enable,
        .port_disable = rtl8366rb_port_disable,
+       .port_change_mtu = rtl8366rb_change_mtu,
+       .port_max_mtu = rtl8366rb_max_mtu,
 };
 
 static const struct realtek_smi_ops rtl8366rb_smi_ops = {