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

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Message-ID: <20221201084302.oodh22xgvwsjmoc3@blmsp>
Date:   Thu, 1 Dec 2022 09:43:02 +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().

Good idea. I will check how regmap's async_write works and if it is
suitable to do the job. I don't want to drop the regmap usage for this
right now.

> 
> Extra bonus if you implement xmit_more() and transfer more than 1 skb
> per SPI transfer.

That's on my todo list, but I am not sure I will get to it soonish.

Thank you Marc!.

Best,
Markus