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net: macb: fix negative max_mtu size for sama5d3 

JML register on probe will return zero . This register is configured
later on macb_init_hw() which is called on open.
Since we have zero, after header and FCS length subtraction we will get
negative max_mtu size. This issue was affecting DSA drivers with MTU support
(for example KSZ9477).

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Reviewed-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Oleksij Rempel 2022-06-17 09:16:07 +02:00 committed by David S. Miller
parent 2c0ab32b73
commit 46e31db55d
1 changed files with 2 additions and 2 deletions
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4
drivers/net/ethernet/cadence/macb_main.c
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@ -4913,8 +4913,8 @@ static int macb_probe(struct platform_device *pdev)
/* MTU range: 68 - 1500 or 10240 */
dev->min_mtu = GEM_MTU_MIN_SIZE;
if (bp->caps & MACB_CAPS_JUMBO)
dev->max_mtu = gem_readl(bp, JML) - ETH_HLEN - ETH_FCS_LEN;
if ((bp->caps & MACB_CAPS_JUMBO) && bp->jumbo_max_len)
dev->max_mtu = bp->jumbo_max_len - ETH_HLEN - ETH_FCS_LEN;
else
dev->max_mtu = ETH_DATA_LEN;