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

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

[Pucha, HimasekharX Reddy]

> -----Original Message-----
> From: Intel-wired-lan <intel-wired-lan-bounces@osuosl.org> On Behalf Of Vinicius 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.gomes@intel.com>; netdev@vger.kernel.org; richardcochran@gmail.com; kurt@linutronix.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 Kicinski <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 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@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 Contingent worker at Intel)

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

[Daiwei Li]

Hi,

It appears this change breaks PTP on the 82580 controller, as ptp4l reports:

> timed out while polling for tx timestamp increasing tx_timestamp_timeout or
> increasing kworker priority may correct this issue, but a driver bug likely
> causes it

The 82580 controller has a hardware bug in which reading TSICR doesn't clear
it. See this thread
https://lore.kernel.org/all/CDCB8BE0.1EC2C%25matthew.vick@intel.com/ where the
bug was confirmed by an Intel employee. Any chance we could add back the ack
for 82580 specifically? Thanks!

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

[Vinicius Costa Gomes]

Daiwei Li <daiweili@gmail.com> writes:

> Hi,
>
> It appears this change breaks PTP on the 82580 controller, as ptp4l reports:
>
>> timed out while polling for tx timestamp increasing tx_timestamp_timeout or
>> increasing kworker priority may correct this issue, but a driver bug likely
>> causes it
>
> The 82580 controller has a hardware bug in which reading TSICR doesn't clear
> it. See this thread
> https://lore.kernel.org/all/CDCB8BE0.1EC2C%25matthew.vick@intel.com/ where the
> bug was confirmed by an Intel employee. Any chance we could add back the ack
> for 82580 specifically? Thanks!

Of course, I'll prepare a patch for that. 

Thanks for digging that one up.


Cheers,
-- 
Vinicius

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

[Daiwei Li]

> Of course, I'll prepare a patch for that.

Excellent, thank you!


On Fri, Aug 9, 2024 at 9:39 AM Vinicius Costa Gomes
<vinicius.gomes@intel.com> wrote:
>
> Daiwei Li <daiweili@gmail.com> writes:
>
> > Hi,
> >
> > It appears this change breaks PTP on the 82580 controller, as ptp4l reports:
> >
> >> timed out while polling for tx timestamp increasing tx_timestamp_timeout or
> >> increasing kworker priority may correct this issue, but a driver bug likely
> >> causes it
> >
> > The 82580 controller has a hardware bug in which reading TSICR doesn't clear
> > it. See this thread
> > https://lore.kernel.org/all/CDCB8BE0.1EC2C%25matthew.vick@intel.com/ where the
> > bug was confirmed by an Intel employee. Any chance we could add back the ack
> > for 82580 specifically? Thanks!
>
> Of course, I'll prepare a patch for that.
>
> Thanks for digging that one up.
>
>
> Cheers,
> --
> Vinicius