bcm4908: fix handling Ethernet frames of size 1506 - 1514

MTU needs to be explicitly set as default value is too low.

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>

diff --git a/target/linux/bcm4908/patches-5.4/170-net-broadcom-bcm4908_enet-set-MTU-on-open-on-request.patch b/target/linux/bcm4908/patches-5.4/170-net-broadcom-bcm4908_enet-set-MTU-on-open-on-request.patch
new file mode 100644 (file)
index 0000000..87cb851
--- /dev/null
+++ b/target/linux/bcm4908/patches-5.4/170-net-broadcom-bcm4908_enet-set-MTU-on-open-on-request.patch
@@ -0,0 +1,113 @@
+From d7dfbcba0437955ccbe4c6db736526d528f27720 Mon Sep 17 00:00:00 2001
+From: =?UTF-8?q?Rafa=C5=82=20Mi=C5=82ecki?= <rafal@milecki.pl>
+Date: Fri, 12 Feb 2021 16:06:00 +0100
+Subject: [PATCH] net: broadcom: bcm4908_enet: set MTU on open & on request
+
+Hardware comes up with default max frame size set to 1518. When using it
+with switch it results in actual Ethernet MTU 1492:
+1518 - 14 (Ethernet header) - 4 (Broadcom's tag) - 4 (802.1q) - 4 (FCS)
+
+Above means hardware in its default state can't handle standard Ethernet
+traffic (MTU 1500).
+
+Define maximum possible Ethernet overhead and always set MAC max frame
+length accordingly. This change fixes handling Ethernet frames of length
+1506 - 1514.
+---
+ drivers/net/ethernet/broadcom/bcm4908_enet.c | 31 ++++++++++++++++----
+ 1 file changed, 25 insertions(+), 6 deletions(-)
+
+--- a/drivers/net/ethernet/broadcom/bcm4908_enet.c
++++ b/drivers/net/ethernet/broadcom/bcm4908_enet.c
+@@ -5,6 +5,7 @@
+ 
+ #include <linux/delay.h>
+ #include <linux/etherdevice.h>
++#include <linux/if_vlan.h>
+ #include <linux/interrupt.h>
+ #include <linux/module.h>
+ #include <linux/of.h>
+@@ -29,9 +30,10 @@
+                                                ENET_DMA_CH_CFG_INT_BUFF_DONE)
+ #define ENET_DMA_MAX_BURST_LEN                        8 /* in 64 bit words */
+ 
+-#define ENET_MTU_MIN                          60
+-#define ENET_MTU_MAX                          1500 /* Is it possible to support 2044? */
+-#define ENET_MTU_MAX_EXTRA_SIZE                       32 /* L2 */
++#define ENET_MTU_MAX                          ETH_DATA_LEN /* Is it possible to support 2044? */
++#define BRCM_MAX_TAG_LEN                      6
++#define ENET_MAX_ETH_OVERHEAD                 (ETH_HLEN + BRCM_MAX_TAG_LEN + VLAN_HLEN + \
++                                               ETH_FCS_LEN + 4) /* 32 */
+ 
+ struct bcm4908_enet_dma_ring_bd {
+       __le32 ctl;
+@@ -135,6 +137,11 @@ static void bcm4908_enet_intrs_ack(struc
+       enet_write(enet, ENET_DMA_CH_RX_CFG + ENET_DMA_CH_CFG_INT_STAT, ENET_DMA_INT_DEFAULTS);
+ }
+ 
++static void bcm4908_enet_set_mtu(struct bcm4908_enet *enet, int mtu)
++{
++      enet_umac_write(enet, UMAC_MAX_FRAME_LEN, mtu + ENET_MAX_ETH_OVERHEAD);
++}
++
+ /***
+  * DMA
+  */
+@@ -246,7 +253,7 @@ static int bcm4908_enet_dma_alloc_rx_buf
+       u32 tmp;
+       int err;
+ 
+-      slot->len = ENET_MTU_MAX + ENET_MTU_MAX_EXTRA_SIZE;
++      slot->len = ENET_MTU_MAX + ENET_MAX_ETH_OVERHEAD;
+ 
+       slot->skb = netdev_alloc_skb(enet->netdev, slot->len);
+       if (!slot->skb)
+@@ -374,6 +381,8 @@ static void bcm4908_enet_gmac_init(struc
+ {
+       u32 cmd;
+ 
++      bcm4908_enet_set_mtu(enet, enet->netdev->mtu);
++
+       cmd = enet_umac_read(enet, UMAC_CMD);
+       enet_umac_write(enet, UMAC_CMD, cmd | CMD_SW_RESET);
+       enet_umac_write(enet, UMAC_CMD, cmd & ~CMD_SW_RESET);
+@@ -559,7 +568,7 @@ static int bcm4908_enet_poll(struct napi
+ 
+               len = (ctl & DMA_CTL_LEN_DESC_BUFLENGTH) >> DMA_CTL_LEN_DESC_BUFLENGTH_SHIFT;
+ 
+-              if (len < ENET_MTU_MIN ||
++              if (len < ETH_ZLEN ||
+                   (ctl & (DMA_CTL_STATUS_SOP | DMA_CTL_STATUS_EOP)) != (DMA_CTL_STATUS_SOP | DMA_CTL_STATUS_EOP)) {
+                       enet->netdev->stats.rx_dropped++;
+                       break;
+@@ -583,11 +592,21 @@ static int bcm4908_enet_poll(struct napi
+       return handled;
+ }
+ 
++static int bcm4908_enet_change_mtu(struct net_device *netdev, int new_mtu)
++{
++      struct bcm4908_enet *enet = netdev_priv(netdev);
++
++      bcm4908_enet_set_mtu(enet, new_mtu);
++
++      return 0;
++}
++
+ static const struct net_device_ops bcm4908_enet_netdev_ops = {
+       .ndo_open = bcm4908_enet_open,
+       .ndo_stop = bcm4908_enet_stop,
+       .ndo_start_xmit = bcm4908_enet_start_xmit,
+       .ndo_set_mac_address = eth_mac_addr,
++      .ndo_change_mtu = bcm4908_enet_change_mtu,
+ };
+ 
+ static int bcm4908_enet_probe(struct platform_device *pdev)
+@@ -625,7 +644,7 @@ static int bcm4908_enet_probe(struct pla
+       eth_hw_addr_random(netdev);
+       netdev->netdev_ops = &bcm4908_enet_netdev_ops;
+       netdev->min_mtu = ETH_ZLEN;
+-      netdev->mtu = ENET_MTU_MAX;
++      netdev->mtu = ETH_DATA_LEN;
+       netdev->max_mtu = ENET_MTU_MAX;
+       netif_napi_add(netdev, &enet->napi, bcm4908_enet_poll, 64);
+