netdev - Re: [EXT] [PATCH] bnx2x: Prevent ptp_task to be rescheduled indefinitely

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Message-ID: <CAHD1Q_xJrVeZXHCpBprErkUXrxFMJ-SPSZ-w1deENcOjcT3tZA@mail.gmail.com>
Date:   Sun, 23 Jun 2019 21:50:28 -0300
From:   Guilherme Piccoli <gpiccoli@...onical.com>
To:     Sudarsana Reddy Kalluru <skalluru@...vell.com>
Cc:     GR-everest-linux-l2 <GR-everest-linux-l2@...vell.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Ariel Elior <aelior@...vell.com>,
        "jay.vosburgh@...onical.com" <jay.vosburgh@...onical.com>
Subject: Re: [EXT] [PATCH] bnx2x: Prevent ptp_task to be rescheduled indefinitely

On Sun, Jun 23, 2019 at 2:13 AM Sudarsana Reddy Kalluru
<skalluru@...vell.com> wrote:
>
> Thanks for uncovering this issue, and the fix.
> With the proposed fix, if HW latches the timestamp after 3 iterations then it would lead to erroneous PTP functionality. When driver receives the next PTP packet, driver sees that timestamp is available in the register and would assign this value (which corresponds to last/skipped ptp packet) to the PTP packet. In general, FW takes around 1ms to 100ms to perform the timestamp and may take more. Hence the promising solution for this issue would be to wait for timestamp for particular period of time. If Tx timestamp is not available for a pre-determined max period, then declare it as an error scenario and terminate the thread.
>
> Just for the reference, similar fix was added for Marvell qede driver recently. Patch details are,
> 9adebac37e7d: (qede: Handle infinite driver spinning for Tx timestamp.)
> https://www.spinics.net/lists/netdev/msg572838.html
>

Thanks a lot for the quick review and good suggestion Sudarsana!
I'll rework the fix based on your reference, and resubmit.

Cheers,


Guilherme