From 893e534e7196ba1dee398e1f77e906d76e8c5a3f Mon Sep 17 00:00:00 2001 From: Sergei Antonov Date: Thu, 27 Oct 2022 14:06:59 +0300 Subject: [PATCH 3/3] net: ftmac100: allow increasing MTU to make most use of single-segment buffers If the FTMAC100 is used as a DSA master, then it is expected that frames which are MTU sized on the wire facing the external switch port (1500 octets in L2 payload, plus L2 header) also get a DSA tag when seen by the host port. This extra tag increases the length of the packet as the host port sees it, and the FTMAC100 is not prepared to handle frames whose length exceeds 1518 octets (including FCS) at all. Only a minimal rework is needed to support this configuration. Since MTU-sized DSA-tagged frames still fit within a single buffer (RX_BUF_SIZE), we just need to optimize the resource management rather than implement multi buffer RX. In ndo_change_mtu(), we toggle the FTMAC100_MACCR_RX_FTL bit to tell the hardware to drop (or not) frames with an L2 payload length larger than 1500. We need to replicate the MACCR configuration in ftmac100_start_hw() as well, since there is a hardware reset there which clears previous settings. The advantage of dynamically changing FTMAC100_MACCR_RX_FTL is that when dev->mtu is at the default value of 1500, large frames are automatically dropped in hardware and we do not spend CPU cycles dropping them. Suggested-by: Vladimir Oltean Signed-off-by: Sergei Antonov --- drivers/net/ethernet/faraday/ftmac100.c | 33 +++++++++++++++++++++++-- 1 file changed, 31 insertions(+), 2 deletions(-) diff --git a/drivers/net/ethernet/faraday/ftmac100.c b/drivers/net/ethernet/faraday/ftmac100.c index 7c571b4515a9..6c8c78018ce6 100644 --- a/drivers/net/ethernet/faraday/ftmac100.c +++ b/drivers/net/ethernet/faraday/ftmac100.c @@ -11,6 +11,7 @@ #include #include #include +#include #include #include #include @@ -28,8 +29,8 @@ #define RX_QUEUE_ENTRIES 128 /* must be power of 2 */ #define TX_QUEUE_ENTRIES 16 /* must be power of 2 */ -#define MAX_PKT_SIZE 1518 #define RX_BUF_SIZE 2044 /* must be smaller than 0x7ff */ +#define MAX_PKT_SIZE RX_BUF_SIZE /* multi-segment not supported */ #if MAX_PKT_SIZE > 0x7ff #error invalid MAX_PKT_SIZE @@ -160,6 +161,7 @@ static void ftmac100_set_mac(struct ftmac100 *priv, const unsigned char *mac) static int ftmac100_start_hw(struct ftmac100 *priv) { struct net_device *netdev = priv->netdev; + unsigned int maccr = MACCR_ENABLE_ALL; if (ftmac100_reset(priv)) return -EIO; @@ -176,7 +178,11 @@ static int ftmac100_start_hw(struct ftmac100 *priv) ftmac100_set_mac(priv, netdev->dev_addr); - iowrite32(MACCR_ENABLE_ALL, priv->base + FTMAC100_OFFSET_MACCR); + /* See ftmac100_change_mtu() */ + if (netdev->mtu > ETH_DATA_LEN) + maccr |= FTMAC100_MACCR_RX_FTL; + + iowrite32(maccr, priv->base + FTMAC100_OFFSET_MACCR); return 0; } @@ -1033,6 +1039,28 @@ static int ftmac100_do_ioctl(struct net_device *netdev, struct ifreq *ifr, int c return generic_mii_ioctl(&priv->mii, data, cmd, NULL); } +static int ftmac100_change_mtu(struct net_device *netdev, int mtu) +{ + struct ftmac100 *priv = netdev_priv(netdev); + unsigned int maccr; + + maccr = ioread32(priv->base + FTMAC100_OFFSET_MACCR); + if (mtu > ETH_DATA_LEN) { + /* process long packets in the driver */ + maccr |= FTMAC100_MACCR_RX_FTL; + } else { + /* Let the controller drop incoming packets greater + * than 1518 (that is 1500 + 14 Ethernet + 4 FCS). + */ + maccr &= ~FTMAC100_MACCR_RX_FTL; + } + iowrite32(maccr, priv->base + FTMAC100_OFFSET_MACCR); + + netdev->mtu = mtu; + + return 0; +} + static const struct net_device_ops ftmac100_netdev_ops = { .ndo_open = ftmac100_open, .ndo_stop = ftmac100_stop, @@ -1040,6 +1068,7 @@ static const struct net_device_ops ftmac100_netdev_ops = { .ndo_set_mac_address = eth_mac_addr, .ndo_validate_addr = eth_validate_addr, .ndo_eth_ioctl = ftmac100_do_ioctl, + .ndo_change_mtu = ftmac100_change_mtu, }; /****************************************************************************** -- 2.34.1