Subject: Re: [PATCH iwl-net v2 2/3] igc: Fix reset adapter logics when tx mode change

From: Vinicius Costa Gomes <[email-masked]>
Date: Wed, 10 Jul 2024 16:44:56 -0700

Faizal Rahim <[email-masked]> writes:

> Following the "igc: Fix TX Hang issue when QBV Gate is close" changes,
> remaining issues with the reset adapter logic in igc_tsn_offload_apply()
> have been observed:
>
> 1. The reset adapter logics for i225 and i226 differ, although they should
>    be the same according to the guidelines in I225/6 HW Design Section
>    7.5.2.1 on software initialization during tx mode changes.
> 2. The i225 resets adapter every time, even though tx mode doesn't change.
>    This occurs solely based on the condition  igc_is_device_id_i225() when
>    calling schedule_work().
> 3. i226 doesn't reset adapter for tsn->legacy tx mode changes. It only
>    resets adapter for legacy->tsn tx mode transitions.
> 4. qbv_count introduced in the patch is actually not needed; in this
>    context, a non-zero value of qbv_count is used to indicate if tx mode
>    was unconditionally set to tsn in igc_tsn_enable_offload(). This could
>    be replaced by checking the existing register
>    IGC_TQAVCTRL_TRANSMIT_MODE_TSN bit.
>
> This patch resolves all issues and enters schedule_work() to reset the
> adapter only when changing tx mode. It also removes reliance on qbv_count.
>
> qbv_count field will be removed in a future patch.
>
> Test ran:
>
> 1. Verify reset adapter behaviour in i225/6:
>    a) Enrol a new GCL
>       Reset adapter observed (tx mode change legacy->tsn)
>    b) Enrol a new GCL without deleting qdisc
>       No reset adapter observed (tx mode remain tsn->tsn)
>    c) Delete qdisc
>       Reset adapter observed (tx mode change tsn->legacy)
>
> 2. Tested scenario from "igc: Fix TX Hang issue when QBV Gate is closed"
>    to confirm it remains resolved.
>
> Fixes: 175c241288c0 ("igc: Fix TX Hang issue when QBV Gate is closed")
> Signed-off-by: Faizal Rahim <[email-masked]>
> Reviewed-by: Simon Horman <[email-masked]>
> ---

There were a quite a few bugs, some of them my fault, on this part of
the code, changing between the modes in the hardware.

So I would like some confirmation that ETF offloading/LaunchTime was
also tested with this change. Just to be sure.

But code-wise, looks good:

Acked-by: Vinicius Costa Gomes <[email-masked]>

Cheers,
-- 
Vinicius