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Date:   Wed, 14 Dec 2022 10:22:01 +0100
From:   Marc Kleine-Budde <mkl@pengutronix.de>
To:     Markus Schneider-Pargmann <msp@baylibre.com>
Cc:     Chandrasekar Ramakrishnan <rcsekar@samsung.com>,
        Wolfgang Grandegger <wg@grandegger.com>,
        linux-can@vger.kernel.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Subject: Re: [PATCH 02/15] can: m_can: Wakeup net queue once tx was issued
Message-ID: <20221214092201.xpb3rnwp5rtvrpkr@pengutronix.de>
References: <20221116205308.2996556-1-msp@baylibre.com>
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On 14.12.2022 10:18:20, Marc Kleine-Budde wrote:
> On 14.12.2022 10:14:06, Markus Schneider-Pargmann wrote:
> > Hi Marc,
> >=20
> > 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.
> > > >=20
> > > > Instead release the queue as soon as the transmit was transferred i=
nto
> > > > the hardware FIFO. We are then ready for the next transmit to be
> > > > transferred.
> > >=20
> > > 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(=
).
> > >=20
> > > Extra bonus if you implement xmit_more() and transfer more than 1 skb
> > > per SPI transfer.
> >=20
> > 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?
>=20
> AFAIK you need BQL support: see 0084e298acfe ("can: mcp251xfd: add BQL su=
pport").
>=20
> The etas_es58x driver implements xmit_more(), I added the Author Vincent
> on Cc.

Have a look at netdev_queue_set_dql_min_limit() in the etas driver.

Marc

--=20
Pengutronix e.K.                 | Marc Kleine-Budde           |
Embedded Linux                   | https://www.pengutronix.de  |
Vertretung West/Dortmund         | Phone: +49-231-2826-924     |
Amtsgericht Hildesheim, HRA 2686 | Fax:   +49-5121-206917-5555 |

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