linux-kernel - RE: [Intel-wired-lan] [iwl-net v2 2/2] igb: Fix missing time sync events

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Date: Tue, 27 Feb 2024 12:04:42 +0000
From: "Pucha, HimasekharX Reddy" <himasekharx.reddy.pucha@...el.com>
To: "Gomes, Vinicius" <vinicius.gomes@...el.com>,
	"intel-wired-lan@...ts.osuosl.org" <intel-wired-lan@...ts.osuosl.org>
CC: "Neftin, Sasha" <sasha.neftin@...el.com>, "Gomes, Vinicius"
	<vinicius.gomes@...el.com>, "netdev@...r.kernel.org"
	<netdev@...r.kernel.org>, "richardcochran@...il.com"
	<richardcochran@...il.com>, "kurt@...utronix.de" <kurt@...utronix.de>,
	"Brandeburg, Jesse" <jesse.brandeburg@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Eric Dumazet
	<edumazet@...gle.com>, "Nguyen, Anthony L" <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 2/2] igb: Fix missing time sync
 events

> -----Original Message-----
> From: Intel-wired-lan <intel-wired-lan-bounces@...osl.org> On Behalf Of Vinicius Costa Gomes
> Sent: Wednesday, February 21, 2024 5:27 AM
> To: intel-wired-lan@...ts.osuosl.org
> Cc: Neftin, Sasha <sasha.neftin@...el.com>; Gomes, Vinicius <vinicius.gomes@...el.com>; netdev@...r.kernel.org; richardcochran@...il.com; kurt@...utronix.de; Brandeburg, Jesse <jesse.brandeburg@...el.com>; linux-kernel@...rkernel.org; Eric Dumazet <edumazet@...gle.com>; Nguyen, Anthony L <anthonyl.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: [Intel-wired-lan] [iwl-net v2 2/2] igb: Fix missing time sync events
>
> Fix "double" clearing of interrupts, which can cause external events
> or timestamps to be missed.
>
> The E1000_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 E1000_TSIRC into 'tsicr';
>     2. handle the interrupts present into 'tsirc' and mark them in 'ack';
>     3. write 'ack' into E1000_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: 00c65578b47b ("igb: enable internal PPS for the i210")
> Acked-by: Richard Cochran <richardcochran@...il.com>
> Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@...el.com>
> ---
>  drivers/net/ethernet/intel/igb/igb_main.c | 23 +++++------------------
>  1 file changed, 5 insertions(+), 18 deletions(-)
>

Tested-by: Pucha Himasekhar Reddy <himasekharx.reddy.pucha@...el.com> (A Contingent worker at Intel)