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

[Marc Kleine-Budde <mkl@pengutronix.de>]

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On 21.01.2022 00:35:43, Angelo Dureghello wrote:
> > Please apply appropriate change and check if the driver still works if
> > you RX with full CAN bus load. Please also test if you can still receive
> > RTR frames.
> > 
> 
> I tested this patch:
> 
> -------------------- drivers/net/can/flexcan/flexcan-core.c index
> 0bff1884d5cc..daeeb6250347 100644
> @@ -296,7 +296,10 @@ static_assert(sizeof(struct flexcan_regs) ==  0x4 * 18
> + 0xfb8);
>  static const struct flexcan_devtype_data fsl_mcf5441x_devtype_data = {
>  	.quirks = FLEXCAN_QUIRK_BROKEN_PERR_STATE |
>  		FLEXCAN_QUIRK_NR_IRQ_3 | FLEXCAN_QUIRK_NR_MB_16 |
> -		FLEXCAN_QUIRK_SUPPPORT_RX_FIFO,
> +		FLEXCAN_QUIRK_USE_RX_MAILBOX |
> +		FLEXCAN_QUIRK_SUPPPORT_RX_FIFO |
> +		FLEXCAN_QUIRK_SUPPPORT_RX_MAILBOX |
> +		FLEXCAN_QUIRK_SUPPPORT_RX_MAILBOX_RTR,
>  };
> 
>  static const struct flexcan_devtype_data fsl_p1010_devtype_data = {
> 
> Bus load PC -> mcf5441x tested by
> 
> ip link set can0 type can bitrate 1000000
> ip link set can0 up
> cangen can0 -g 0
> 
> On target (mcf54415)
> candump can0
> 
> It works, even better then FIFO mode.

What's the difference, does it produce less overruns?

> While unfortunately, RTR rx does not work. Tested it by putting
> a trace in flexcan_mailbox_read()
> 
> 	if (reg_ctrl & FLEXCAN_MB_CNT_RTR) {
> 		printk("%s() RX RTR frame\n", __func__);
> 		cfd->can_id |= CAN_RTR_FLAG;
> 	}
> 
> on host pc i used:
> 
> cangen can0 -R
> 
> No sign of RTR in rx. While in FIFO mode i can see it.

Ok, then I enable the mailbox support for the mcf5441x and fix the note
that the IP core doesn't support RTR reception via mailboxes. See the
following patch:

| https://lore.kernel.org/all/20220121084425.3141218-1-mkl@pengutronix.de

If you have time, please test and add your Tested-by.

You can switch to mailbox mode during runtime, if the interface is down:

| ethtool --set-priv-flags can0 rx-rtr off

With ethtool you can query the number of used RX and TX buffers:

| ethtool --show-ring can0

The FIFO mode uses 6 RX buffers, while mailbox mode will probably use
14.

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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