Re: mcf5441x: flexcan FIFO and mailbox mode (was: Re: [PATCH v5 5/5] can: flexcan: add mcf5441x support)

[Angelo Dureghello <angelo@kernel-space.org>]

Hi Marc,

On Thu, 6 Jan 2022, Marc Kleine-Budde wrote:

> Hello Angelo,
>
> On 02.07.2021 11:48:41, Angelo Dureghello wrote:
>> Add flexcan support for NXP ColdFire mcf5441x family.
>>
>> This flexcan module is quite similar to imx6 flexcan module, but
>> with some exceptions:
>>
>> - 3 separate interrupt sources, MB, BOFF and ERR,
>> - implements 16 mb only,
>> - m68k architecture is not supporting devicetrees, so a
>>   platform data check/case has been added,
>> - ColdFire is m68k, so big-endian cpu, with a little-endian flexcan
>>   module.
>
> we're currently discussing the option that the user of a flexcan can
> switch between RX-FIFO and RX via mailboxes.
>
> I noticed that the mcf5441x currently is configured for FIFO mode. Have
> you tested the driver in mailbox mode?
>
> The reason that some cores use the FIFO mode is, that they cannot
> receive RTR CAN frames in mailbox mode. According to the IP core
> overview table, the mcf5441x can receive RTR frames.
>
> If the IP core supports reception of RTR frames, mailbox mode should be
> used, as it makes use of more buffers (16-2) instead of 6 in FIFO mode.
> Should we activate mailbox mode for the mcf5441x?
>

Ok, not sure why i selected FIFO mode initially, my application
actually is quite simple. Will try the switch to mailbox, sure,
looking into this.


> regards,
> Marc
>

Regards,
angelo

> -- 
> 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 |
>