linux-kernel - Re: [PATCH v5 10/12] can: m_can: Use tx_fifo_in_flight for netif

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Message-ID: <ZLlYc6HGZcdJ1N2y@corigine.com>
Date:   Thu, 20 Jul 2023 16:53:23 +0100
From:   Simon Horman <simon.horman@...igine.com>
To:     Markus Schneider-Pargmann <msp@...libre.com>
Cc:     Marc Kleine-Budde <mkl@...gutronix.de>,
        Chandrasekar Ramakrishnan <rcsekar@...sung.com>,
        Wolfgang Grandegger <wg@...ndegger.com>,
        Vincent MAILHOL <mailhol.vincent@...adoo.fr>,
        "David S . Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, linux-can@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Julien Panis <jpanis@...libre.com>
Subject: Re: [PATCH v5 10/12] can: m_can: Use tx_fifo_in_flight for
 netif_queue control

On Tue, Jul 18, 2023 at 09:57:06AM +0200, Markus Schneider-Pargmann wrote:
> The network queue is currently always stopped in start_xmit and
> continued in the interrupt handler. This is not possible anymore if we
> want to keep multiple transmits in flight in parallel.
> 
> Use the previously introduced tx_fifo_in_flight counter to control the
> network queue instead. This has the benefit of not needing to ask the
> hardware about fifo status.
> 
> This patch stops the network queue in start_xmit if the number of
> transmits in flight reaches the size of the fifo and wakes up the queue
> from the interrupt handler once the transmits in flight drops below the
> fifo size. This means any skbs over the limit will be rejected
> immediately in start_xmit (it shouldn't be possible at all to reach that
> state anyways).
> 
> The maximum number of transmits in flight is the size of the fifo.
> 
> Signed-off-by: Markus Schneider-Pargmann <msp@...libre.com>

Reviewed-by: Simon Horman <simon.horman@...igine.com>