linux-kernel - Re: [Intel-wired-lan] [iwl-net v2 1/2] igc: Fix missing time sync events

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Date: Wed, 6 Mar 2024 10:38:33 +0200
From: "naamax.meir" <naamax.meir@...ux.intel.com>
To: Vinicius Costa Gomes <vinicius.gomes@...el.com>,
 intel-wired-lan@...ts.osuosl.org
Cc: sasha.neftin@...el.com, netdev@...r.kernel.org, richardcochran@...il.com,
 kurt@...utronix.de, jesse.brandeburg@...el.com,
 linux-kernel@...r.kernel.org, Eric Dumazet <edumazet@...gle.com>,
 anthony.l.nguyen@...el.com, Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 "David S. Miller" <davem@...emloft.net>
Subject: Re: [Intel-wired-lan] [iwl-net v2 1/2] igc: Fix missing time sync
 events

On 2/21/2024 01:57, Vinicius Costa Gomes wrote:
> Fix "double" clearing of interrupts, which can cause external events
> or timestamps to be missed.
> 
> The IGC_TSIRC Time Sync Interrupt Cause register can be cleared in two
> ways, by either reading it or by writing '1' into the specific cause
> bit. This is documented in section 8.16.1.
> 
> The following flow was used:
>   1. read IGC_TSIRC into 'tsicr';
>   2. handle the interrupts present in 'tsirc' and mark them in 'ack';
>   3. write 'ack' into IGC_TSICR;
> 
> As both (1) and (3) will clear the interrupt cause, if the same
> interrupt happens again between (1) and (3) it will be ignored,
> causing events to be missed.
> 
> Remove the extra clear in (3).
> 
> Fixes: 2c344ae24501 ("igc: Add support for TX timestamping")
> Reviewed-by: Kurt Kanzenbach <kurt@...utronix.de>
> Tested-by: Kurt Kanzenbach <kurt@...utronix.de> # Intel i225
> Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@...el.com>
> ---
>   drivers/net/ethernet/intel/igc/igc_main.c | 12 +-----------
>   1 file changed, 1 insertion(+), 11 deletions(-)

Tested-by: Naama Meir <naamax.meir@...ux.intel.com>