Re: Queries on CAN frame work

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

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On 21.02.2022 14:43:57, Srinivas Neeli wrote:
> > Can you please provide me:
> > - the bit timing constants of the IP core for the arbitration and data
> >   phase
> > - the bit rate for the arbitration and data phase
> >   (especially where the framework calculates not common prescalers)
> > - the clock rate of the CAN bus clock
> > 
> > Can you also provide the hand calculated bit timing parameters for the
> > above scenarios?
> 
> Baud rate 1/5Mbps
> ================
> root@xilinx-vck190-2021_1:~# ip link set can6 type can bitrate 1000000 dbitrate 5000000 fd on   
> [   26.837057] xilinx_can ff070000.can can6: bitrate error 0.0%
> [   26.842731] xilinx_can ff070000.can can6: bitrate error 0.0%
>  can6 txqroot@xilinx-vck190-2021_1:~# ifconfig can6 txqueuelen 1000
>  root@xilinx-vck190-2021_1:~# ip link set can6 up
> [   27.340880] IPv6: ADDRCONF(NETDEV_CHANGE): can6: link becomes ready
> root@xilinx-vck190-2021_1:~# ip -d -s link show can6
>  can6: <NOARP,UP,LOWER_UP,ECHO> mtu 72 qdisc pfifo_fast state UP mode DEFAULT group default qlen 1000
>     link/can  promiscuity 0 minmtu 0 maxmtu 0 
>     can <FD> state ERROR-ACTIVE (berr-counter tx 0 rx 0) restart-ms 0 
> 	  bitrate 999999 sample-point 0.750 
> 	  tq 250 prop-seg 1 phase-seg1 1 phase-seg2 1 sjw 1
> 	  xilinx_can: tseg1 1..256 tseg2 1..128 sjw 1..128 brp 1..256 brp-inc 1
> 	  dbitrate 4999999 dsample-point 0.750 
> 	  dtq 50 dprop-seg 1 dphase-seg1 1 dphase-seg2 1 dsjw 1
> 	  xilinx_can: dtseg1 1..32 dtseg2 1..16 dsjw 1..16 dbrp 1..256 dbrp-inc 1
> 	  clock 79999999 
> 	  re-started bus-errors arbit-lost error-warn error-pass bus-off
> 	  0          0          0          0          0          0         numtxqueues 1 numrxqueues 1 gso_max_size 65536 gso_max_segs 65535 
>     RX: bytes  packets  errors  dropped overrun mcast   
>     0          0        0       0       0       0       
>     TX: bytes  packets  errors  dropped carrier collsns 
>     0          0        0       0       0       0

Are you using the mainline xilinx_can driver? The "ip" command says,
you're using:

>  sjw 1..128  brp 1..256
> dsjw 1..16  dbrp 1..256

Looking at the mainline xilinx driver, we have:

| /* CAN Bittiming constants as per Xilinx CAN specs */
| static const struct can_bittiming_const xcan_bittiming_const = {
| 	.name = DRIVER_NAME,
| 	.tseg1_min = 1,
| 	.tseg1_max = 16,
| 	.tseg2_min = 1,
| 	.tseg2_max = 8,
| 	.sjw_max = 4,
                   ^
Does not match due to "sjw 1..128".

| 	.brp_min = 1,
| 	.brp_max = 256,
| 	.brp_inc = 1,
| };
| 
| /* AXI CANFD Arbitration Bittiming constants as per AXI CANFD 1.0 spec */
| static const struct can_bittiming_const xcan_bittiming_const_canfd = {
| 	.name = DRIVER_NAME,
| 	.tseg1_min = 1,
| 	.tseg1_max = 64,
| 	.tseg2_min = 1,
| 	.tseg2_max = 16,
| 	.sjw_max = 16,
                   ^^
Does not match due to "sjw 1..128".

| 	.brp_min = 1,
| 	.brp_max = 256,
| 	.brp_inc = 1,
| };
| 
| /* AXI CANFD Data Bittiming constants as per AXI CANFD 1.0 specs */
| static struct can_bittiming_const xcan_data_bittiming_const_canfd = {
| 	.name = DRIVER_NAME,
| 	.tseg1_min = 1,
| 	.tseg1_max = 16,
| 	.tseg2_min = 1,
| 	.tseg2_max = 8,
| 	.sjw_max = 8,
                   ^
Does not match due to "dsjw 1..16"

| 	.brp_min = 1,
| 	.brp_max = 256,
| 	.brp_inc = 1,
| };
| 
| /* AXI CANFD 2.0 Arbitration Bittiming constants as per AXI CANFD 2.0 spec */
| static const struct can_bittiming_const xcan_bittiming_const_canfd2 = {
| 	.name = DRIVER_NAME,
| 	.tseg1_min = 1,
| 	.tseg1_max = 256,
| 	.tseg2_min = 1,
| 	.tseg2_max = 128,
| 	.sjw_max = 128,
| 	.brp_min = 2,
                   ^
Does not match due to "brp 1..256".

| 	.brp_max = 256,
| 	.brp_inc = 1,
| };
| 
| /* AXI CANFD 2.0 Data Bittiming constants as per AXI CANFD 2.0 spec */
| static struct can_bittiming_const xcan_data_bittiming_const_canfd2 = {
| 	.name = DRIVER_NAME,
| 	.tseg1_min = 1,
| 	.tseg1_max = 32,
| 	.tseg2_min = 1,
| 	.tseg2_max = 16,
| 	.sjw_max = 16,
| 	.brp_min = 2,
                   ^
Does not match due to "dbrp 1..256".

| 	.brp_max = 256,
| 	.brp_inc = 1,
| };

Can you send patches to update the xilinx CAN driver?

I'm continue working on the CAN bittiming code.

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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