[PATCH v1 0/1] Adjust macb max_tx_len for mpfs

[<daire.mcnamara@microchip.com>]

From: Daire McNamara <daire.mcnamara@microchip.com>

Several customers have reported unexpected ethernet issues whereby
the GEM stops transmitting and receiving. Performing an action such
as ifconfig <ethX> down; ifconfig <ethX> up clears this particular
condition.

The origin of the issue is a stream of AMBA_ERRORS (bit 6) from the
tx queues.

This patch sets the max_tx_length to SRAM size (16 KiB
in the case of mpfs) divided by num_queues (4 in the case of mpfs)
and then subtracts 56 bytes from that figure - resulting in max_tx_len
of 4040.  The max jumbo length is also set to 4040.  These figures
are derived from Cadence erratum 1686.

Daire McNamara (1):
  net: macb: Shorten max_tx_len to 4KiB - 56 on mpfs

 drivers/net/ethernet/cadence/macb.h      |  1 +
 drivers/net/ethernet/cadence/macb_main.c | 16 ++++++++++++----
 2 files changed, 13 insertions(+), 4 deletions(-)


base-commit: 7a124d3a4a346563967b8887882858e5ef46f030
prerequisite-patch-id: 08908afdfe3b919f92560dd4306178c5f3f588dd
-- 
2.25.1