Commit 363a99af authored by Charles Perry's avatar Charles Perry Committed by Paolo Abeni
Browse files

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: default avatarCharles Perry <charles.perry@microchip.com>
Reviewed-by: default avatarSimon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20260313140610.3681752-3-charles.perry@microchip.com


Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
parent 63e9d434

drivers/net/ethernet/cadence/macb_main.c

+4 −2
Original line number Diff line number Diff line
@@ -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;