Re: [PATCH net-next v2 10/12] net: dsa: rzn1-a5psw: Add fixed frame length workaround for management port

[Jakub Kicinski <kuba@kernel.org>]

On Thu,  1 Oct 2026 16:43:23 +0100 Prabhakar wrote:
> From: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
> 
> The ETHSW IP used in SoCs such as RZ/T2H and RZ/N2H has a hardware issue
> where the internal mgmt_tag_vld signal is asserted as a level instead of
> a single-cycle pulse. This causes the frame length counter on the
> management (CPU) port to over-increment, so valid frames are falsely
> detected as oversized and dropped.
> 
> The recommended workaround is to program the maximum frame length
> register (FRM_LENGTH) of the management port with a fixed, large value.
> 
> Add a management_port_fixed_frame_len member to struct a5psw_of_data to
> hold the SoC-specific value. When it is set, program A5PSW_FRM_LENGTH
> for the CPU port with this value in a5psw_setup(), and skip updating
> FRM_LENGTH for the CPU port in a5psw_port_change_mtu() so that MTU
> changes do not override the workaround.
> 
> No functional change for existing SoCs, which leave the value unset.

drivers/net/dsa/rzn1_a5psw.c:212:24: error: initializing 'struct a5psw_of_data *' with an expression of type 'const struct a5psw_of_data *' discards qualifiers [-Werror,-Wincompatible-pointer-types-discards-qualifiers]
  212 |         struct a5psw_of_data *of_data = a5psw->of_data;
      |                               ^         ~~~~~~~~~~~~~~
-- 
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