Subject: Re: [Intel-wired-lan] [PATCH iwl-net v2 1/3] igc: Fix qbv_config_change_errors logics

From: Mor Bar-Gabay <[email-masked]>
Date: Thu, 1 Aug 2024 10:32:42 +0300

On 07/07/2024 15:53, Faizal Rahim wrote:
> When user issues these cmds:
> 1. Either a) or b)
>     a) mqprio with hardware offload disabled
>     b) taprio with txtime-assist feature enabled
> 2. etf
> 3. tc qdisc delete
> 4. taprio with base time in the past
> 
> At step 4, qbv_config_change_errors wrongly increased by 1.
> 
> Excerpt from IEEE 802.1Q-2018 8.6.9.3.1:
> "If AdminBaseTime specifies a time in the past, and the current schedule
> is running, then: Increment ConfigChangeError counter"
> 
> qbv_config_change_errors should only increase if base time is in the past
> and no taprio is active. In user perspective, taprio was not active when
> first triggered at step 4. However, i225/6 reuses qbv for etf, so qbv is
> enabled with a dummy schedule at step 2 where it enters
> igc_tsn_enable_offload() and qbv_count got incremented to 1. At step 4, it
> enters igc_tsn_enable_offload() again, qbv_count is incremented to 2.
> Because taprio is running, tc_setup_type is TC_SETUP_QDISC_ETF and
> qbv_count > 1, qbv_config_change_errors value got incremented.
> 
> This issue happens due to reliance on qbv_count field where a non-zero
> value indicates that taprio is running. But qbv_count increases
> regardless if taprio is triggered by user or by other tsn feature. It does
> not align with qbv_config_change_errors expectation where it is only
> concerned with taprio triggered by user.
> 
> Fixing this by relocating the qbv_config_change_errors logic to
> igc_save_qbv_schedule(), eliminating reliance on qbv_count and its
> inaccuracies from i225/6's multiple uses of qbv feature for other TSN
> features.
> 
> The new function created: igc_tsn_is_taprio_activated_by_user() uses
> taprio_offload_enable field to indicate that the current running taprio
> was triggered by user, instead of triggered by non-qbv feature like etf.
> 
> Fixes: ae4fe4698300 ("igc: Add qbv_config_change_errors counter")
> Signed-off-by: Faizal Rahim <[email-masked]>
> Reviewed-by: Simon Horman <[email-masked]>
> Acked-by: Vinicius Costa Gomes <[email-masked]>
> ---
>   drivers/net/ethernet/intel/igc/igc_main.c |  8 ++++++--
>   drivers/net/ethernet/intel/igc/igc_tsn.c  | 16 ++++++++--------
>   drivers/net/ethernet/intel/igc/igc_tsn.h  |  1 +
>   3 files changed, 15 insertions(+), 10 deletions(-)
> 
Tested-by: Mor Bar-Gabay <[email-masked]>