linux-kernel - Re: [PATCH 02/15] can: m_can: Wakeup net queue once tx was issued

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Message-ID: <20221214091406.g6vim5hvlkm34naf@blmsp>
Date:   Wed, 14 Dec 2022 10:14:06 +0100
From:   Markus Schneider-Pargmann <msp@...libre.com>
To:     Marc Kleine-Budde <mkl@...gutronix.de>
Cc:     Chandrasekar Ramakrishnan <rcsekar@...sung.com>,
        Wolfgang Grandegger <wg@...ndegger.com>,
        linux-can@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 02/15] can: m_can: Wakeup net queue once tx was issued

Hi Marc,

On Wed, Nov 30, 2022 at 06:21:00PM +0100, Marc Kleine-Budde wrote:
> On 16.11.2022 21:52:55, Markus Schneider-Pargmann wrote:
> > Currently the driver waits to wakeup the queue until the interrupt for
> > the transmit event is received and acknowledged. If we want to use the
> > hardware FIFO, this is too late.
> > 
> > Instead release the queue as soon as the transmit was transferred into
> > the hardware FIFO. We are then ready for the next transmit to be
> > transferred.
> 
> If you want to really speed up the TX path, remove the worker and use
> the spi_async() API from the xmit callback, see mcp251xfd_start_xmit().
> 
> Extra bonus if you implement xmit_more() and transfer more than 1 skb
> per SPI transfer.

Just a quick question here, I mplemented a xmit_more() call and I am
testing it right now, but it always returns false even under high
pressure. The device has a txqueuelen set to 1000. Do I need to turn
some other knob for this to work?

Thanks,
Markus