Re: [PATCH net v2 6/6] net: stmmac: selftests: Account for alignment shift on dwmac1000 for Jumbo test

On dwmac1000, we currently only support single-descriptor frames. The
Jumbo test started failing when NET_IP_ALIGN was added to align the IP
header, as this tests tries to send the biggest possible frame.

On dwmac1000 the DMA transfer is aligned on 4-bytes, so adding a 2-byte
shift at the start-of-buffer address means it takes a whole extra 
4-byte
DMA burst to receive the Jumbo packet, causing it to spill over the 
next
descriptor.

This doesn't seem to happen on dwmac4 and xgmac that appear to 
correctly
handle unaligned xfers (only tested on dwmac4)

Let's account for that in the Jumbo test, reduce the size of our big
packet by the align size.

Fixes: 23680bf5f8c6 ("net: stmmac: restore NET_IP_ALIGN in the RX DMA 
offset")
Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_selftests.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_selftests.c 

b/drivers/net/ethernet/stmicro/stmmac/stmmac_selftests.c
index ec56ee0031ab..fc8d69260f43 100644

--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_selftests.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_selftests.c

@@ -1776,6 +1776,9 @@ static int __stmmac_test_jumbo(struct stmmac_priv 

*priv, u16 queue)
 	struct stmmac_packet_attrs attr = { };
 	int size = priv->dma_conf.dma_buf_sz;

+	if (!dwmac_is_xmac(priv->plat->core_type))
+		size -= NET_IP_ALIGN;
+
 	attr.dst = priv->dev->dev_addr;
 	attr.max_size = size - ETH_FCS_LEN;
 	attr.queue_mapping = queue;