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From: "Pucha, HimasekharX Reddy" <himasekharx.reddy.pucha@intel.com>
To: "Gomes, Vinicius" <vinicius.gomes@intel.com>,
	"intel-wired-lan@lists.osuosl.org" <intel-wired-lan@lists.osuosl.org>
CC: "Neftin, Sasha" <sasha.neftin@intel.com>, "Gomes, Vinicius"
	<vinicius.gomes@intel.com>, "netdev@vger.kernel.org"
	<netdev@vger.kernel.org>, "richardcochran@gmail.com"
	<richardcochran@gmail.com>, "kurt@linutronix.de" <kurt@linutronix.de>,
	"Brandeburg, Jesse" <jesse.brandeburg@intel.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, Eric Dumazet
	<edumazet@google.com>, "Nguyen, Anthony L" <anthony.l.nguyen@intel.com>,
	"Jeff Kirsher" <jeffrey.t.kirsher@intel.com>, Jakub Kicinski
	<kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>, "David S. Miller"
	<davem@davemloft.net>
Subject: RE: [Intel-wired-lan] [iwl-net v2 2/2] igb: Fix missing time sync
 events
Thread-Topic: [Intel-wired-lan] [iwl-net v2 2/2] igb: Fix missing time sync
 events
Thread-Index: AQHaZFicYiO+YWPXJ0KsPZBJcKpe8LEeISfg
Date: Tue, 27 Feb 2024 12:04:42 +0000
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References: <20240220235712.241552-1-vinicius.gomes@intel.com>
 <20240220235712.241552-3-vinicius.gomes@intel.com>
In-Reply-To: <20240220235712.241552-3-vinicius.gomes@intel.com>
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> -----Original Message-----
> From: Intel-wired-lan <intel-wired-lan-bounces@osuosl.org> On Behalf Of V=
inicius Costa Gomes
> Sent: Wednesday, February 21, 2024 5:27 AM
> To: intel-wired-lan@lists.osuosl.org
> Cc: Neftin, Sasha <sasha.neftin@intel.com>; Gomes, Vinicius <vinicius.gom=
es@intel.com>; netdev@vger.kernel.org; richardcochran@gmail.com; kurt@linut=
ronix.de; Brandeburg, Jesse <jesse.brandeburg@intel.com>; linux-kernel@vger=
kernel.org; Eric Dumazet <edumazet@google.com>; Nguyen, Anthony L <anthony=
l.nguyen@intel.com>; Jeff Kirsher <jeffrey.t.kirsher@intel.com>; Jakub Kic=
inski <kuba@kernel.org>; Paolo Abeni <pabeni@redhat.com>; David S. Miller <=
davem@davemloft.net>
> Subject: [Intel-wired-lan] [iwl-net v2 2/2] igb: Fix missing time sync ev=
ents
>
> 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@gmail.com>
> Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@intel.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@intel.com> (A Co=
ntingent worker at Intel)