Re: [PATCH net v4 5/7] net: stmmac: dwmac4: Use the correct bufzise when the len is exactly 8K

On 9/18/26 14:25, Nicolai Buchwitz wrote:

Hi Maxime

On 17.9.2026 23:53, Maxime Chevallier wrote:

quoted

DMA bufsize selection isn't made on the MTU but the actual frame length,
so including the L2 header. On DWMAC4, if the len is exactly BUF_SIZE_8KiB,
the next larger size is incorrectly selected.

Lets fix the comparison and while at it, rename the parameter from len
to mtu.

Isn't it "[...] from mtu to len"?

:(

Bah, if respin is required I'll fix this

quoted

Fixes: c3efed5ad1b0 ("net: stmmac: Enable dwmac4 jumbo frame more than 8KiB").
Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
---
 drivers/net/ethernet/stmicro/stmmac/dwmac4_descs.c | 4 ++--
 drivers/net/ethernet/stmicro/stmmac/hwif.h         | 2 +-
 drivers/net/ethernet/stmicro/stmmac/ring_mode.c    | 4 ++--
 3 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac4_descs.c b/drivers/net/ethernet/stmicro/stmmac/dwmac4_descs.c
index 2994df41ec2c..c6a8f8d73501 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac4_descs.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac4_descs.c

@@ -474,11 +474,11 @@ static void dwmac4_set_sarc(struct dma_desc *p, u32 sarc_type)

                       sarc_type));
 }

-static int set_16kib_bfsize(int mtu)
+static int set_16kib_bfsize(int len)
 {
     int ret = 0;

-    if (unlikely(mtu >= BUF_SIZE_8KiB))
+    if (unlikely(len > BUF_SIZE_8KiB))

Should we drop set_16kib_bfsize() instead?

After 6/7 it looks to me like the same test as the first branch of
stmmac_set_bfsize(). The caller ends up there anyway when it returns 0
and chain_mode_ops doesn't have it at all.

True yeah :) however maybe we can wait for this to be merged and have the
cleanup in net-next ?

Sashiko is getting crazy with the "pre-existing issues" everytime we touch
stmmac, cleanups are long overdue and this could be included in there :(

Maxime