Hi Marc,
> -----Original Message-----
> From: Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx>
> Sent: Friday, March 18, 2022 3:31 AM
> To: Srinivas Neeli <sneeli@xxxxxxxxxx>
> Cc: Srinivas Goud <sgoud@xxxxxxxxxx>; Naveen Kumar Gaddipati
> <naveenku@xxxxxxxxxx>; Prasad Beer Prasad <prasadbe@xxxxxxxxxx>; linux-
> can <linux-can@xxxxxxxxxxxxxxx>; Stefan Mätje <stefan.maetje@xxxxxx>;
> Vincent MAILHOL <mailhol.vincent@xxxxxxxxxx>
> Subject: Re: Queries on CAN frame work
>
> 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:
Yes , mainline and internal drivers are same.
Xilinx maintains common driver for multiple CAN and CANFD IP's.
Xilinx supports below CAN IP's:
xlnx,zynq-can-1.0 (zynq platform & zynqmp platform)
xlnx,axi-can-1.00.a ( Soft IP version 1.00)
xlnx,canfd-1.0 (Soft canfd ip version 1.0)
xlnx,canfd-2.0(Soft canfd ip Version 2.0)
xlnx,canfd2.0 equal to versal canfd ip, so using same compatible string for both.
For each ip sjw_max and brp values are different.
Due to this reason created multiple bit timing structures.
>
> > 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".
Versal early silicon we observed bit enlarging issue with brp =1 in side IP using simulaitons(Not observed on software side) , but it fixed in production silicon.
Plan to revert this patch to support TDC feature(To support higher baud rates we need brp =1).
>
> | .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 |
