Re: can, tcan4x5x: look to merge rpi support into rpi kernel tree - Marc Kleine-Budde

From: Marc Kleine-Budde <mkl@pengutronix.de>
To: Torin Cooper-Bennun <torin@maxiluxsystems.com>
Cc: linux-can <linux-can@vger.kernel.org>
Subject: Re: can, tcan4x5x: look to merge rpi support into rpi kernel tree
Date: Tue, 16 Feb 2021 12:19:30 +0100	[thread overview]
Message-ID: <20210216111930.pcg4e7cildzuri6d@hardanger.blackshift.org> (raw)
In-Reply-To: <CAALJrqiVdmLQr7q2ijbWq70RD6PTD8PtVX_zmLW9=uNdc57WqA@mail.gmail.com>

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Please keep the mailing list on Cc.

On 16.02.2021 11:11:34, Torin Cooper-Bennun wrote:
> On Tue, 16 Feb 2021 at 10:28, Marc Kleine-Budde <mkl@pengutronix.de> wrote:
> > You might not, but the driver does :)
> 
> Indeed, on closer inspection I can see that!
> 
> > If the process repeats infinitely then the CAN controller doesn't go
> > into bus-off, which means the CAN bus is terminated correctly.
> >
> > With your setup of only one node on the bus and correct termination, I
> > too think the frame should be send until the ACK field. I suggest to
> > first create a working CAN bus setup and then add the tcan to it.
> 
> I have to thank you for mentioning termination, because it turned out
> I had not used correct termination at all. How embarrassing! With that
> fixed, the transceiver is happy and I have working TX and RX.

\o/

> Mostly working RX, anyway. When putting the interface down and then
> back up (but allowing a second node to continue attempting TX in the
> meantime) I see some blank frames...
> 
> can0  001   [8]  00 01 02 03 04 05 06 07
> can0  001   [8]  00 01 02 03 04 05 06 07
> can0  001   [8]  00 01 02 03 04 05 06 07
> can0  000   [0]
> can0  000   [0]
> can0  001   [8]  00 01 02 03 04 05 06 07
> can0  001   [8]  00 01 02 03 04 05 06 07
> etc.
> 
> (where the 8-byte frame is what the bus is actually seeing.)

Where do you see these blank frames? On the sending rpi with candump? An
on the bus (with a second system) you only see the full 8 byte long
frames?

Use "candump any,0~0,#FFFFFFFF -extA" to get RX/TX annotation.
Use "cangen -Ii -L8 -D000102030405060708 -g100 can0" to get increasing
CAN-IDs, so you can figure out if a CAN frame got lost.

Seems I have to add the TX path to the list of broken things...

The mcp251xfd driver can be used as a template for the tcan4x5x driver.

regards,
Marc

-- 
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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