From: Charles Perry Date: Fri, 13 Mar 2026 14:06:09 +0000 (-0700) Subject: net: macb: add safeguards for jumbo frame larger than 10240 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=363a99af19a7f5c7ddd7571e39f3ae6663397bb6;p=thirdparty%2Flinux.git net: macb: add safeguards for jumbo frame larger than 10240 The RX buffers for GEM can have a maximum size of 16320 bytes (0xff in the RXBS field of the DMACFG register means 255*64 = 16320 bytes). The GEM IP has configurable maximum jumbo frame length that can go up to 16383. The actual value for this limit can be found in the "jumbo_max_length" field (bits 0..13) of the DCFG2 register. Currently, the macb driver doesn't use the DCFG2 register when determining the max MTU, instead an hardcoded value (jumbo_max_len in struct macb_config) is used for each platform. Right now the maximum value for jumbo_max_len is 10240 (0x2800). GEM uses one buffer per packet which means that one buffer must allow room for the max MTU plus L2 encapsulation and alignment. This is a limitation of the driver. This commit adds a limit to max_mtu and rx_buffer_size so that the RXBS field can never overflow when a large MTU is used. With this commit, it is now possible to add new platforms with a jumbo_max_len of 16383 so that the hardware properties of each IP can be properly captured in struct macb_config. Signed-off-by: Charles Perry Reviewed-by: Simon Horman Link: https://patch.msgid.link/20260313140610.3681752-3-charles.perry@microchip.com Signed-off-by: Paolo Abeni --- diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c index 63105a5f46a7d..ca6f9e2a4eb4c 100644 --- a/drivers/net/ethernet/cadence/macb_main.c +++ b/drivers/net/ethernet/cadence/macb_main.c @@ -50,6 +50,7 @@ struct sifive_fu540_macb_mgmt { #define MACB_RX_BUFFER_SIZE 128 #define RX_BUFFER_MULTIPLE 64 /* bytes */ +#define RX_BUFFER_MAX (0xFF * RX_BUFFER_MULTIPLE) /* 16320 bytes */ #define DEFAULT_RX_RING_SIZE 512 /* must be power of 2 */ #define MIN_RX_RING_SIZE 64 @@ -2601,7 +2602,7 @@ static void macb_init_rx_buffer_size(struct macb *bp, size_t size) if (!macb_is_gem(bp)) { bp->rx_buffer_size = MACB_RX_BUFFER_SIZE; } else { - bp->rx_buffer_size = size; + bp->rx_buffer_size = MIN(size, RX_BUFFER_MAX); if (bp->rx_buffer_size % RX_BUFFER_MULTIPLE) { netdev_dbg(bp->dev, @@ -5791,7 +5792,8 @@ static int macb_probe(struct platform_device *pdev) /* MTU range: 68 - 1518 or 10240 */ dev->min_mtu = GEM_MTU_MIN_SIZE; if ((bp->caps & MACB_CAPS_JUMBO) && bp->jumbo_max_len) - dev->max_mtu = bp->jumbo_max_len - ETH_HLEN - ETH_FCS_LEN; + dev->max_mtu = MIN(bp->jumbo_max_len, RX_BUFFER_MAX) - + ETH_HLEN - ETH_FCS_LEN; else dev->max_mtu = 1536 - ETH_HLEN - ETH_FCS_LEN;