Hello,
We faced some issues with CAN when we installed the latest jetpack (4.5.1) onto a xavier. On an older installation CAN worked fine on 500 kbit/s.
I discovered that the CAN peripheral is now clocked with another parent clock. I followed the guide on updating the parent clock in the kernel-dtb file and the bpmp-dtb file.
This was the output in case CAN does not work properly:
$ ip -det link
...
10: can0: <NOARP,UP,LOWER_UP,ECHO> mtu 72 qdisc pfifo_fast state UP mode DEFAULT group default qlen 100
link/can promiscuity 0
can <BERR-REPORTING,FD> state ERROR-PASSIVE (berr-counter tx 0 rx 127) restart-ms 0
bitrate 498701 sample-point 0.870
tq 26 prop-seg 33 phase-seg1 33 phase-seg2 10 sjw 1
mttcan: tseg1 2..255 tseg2 0..127 sjw 1..127 brp 1..511 brp-inc 1
dbitrate 2021052 dsample-point 0.736
dtq 26 dprop-seg 6 dphase-seg1 7 dphase-seg2 5 dsjw 1
mttcan: dtseg1 1..31 dtseg2 0..15 dsjw 1..15 dbrp 1..15 dbrp-inc 1
clock 38400000numtxqueues 1 numrxqueues 1 gso_max_size 65536 gso_max_segs 65535
...
I modified bootloader/t186ref/tegra194-a02-bpmp-p2888-a04.dtb:
clock@can1 {
allow_fractional_divider = <0x1>;
- allowed-parents = <0x121 0x5b 0x13a>;
+ allowed-parents = <0x121 0x5b 0x5e 0x13a>;
clk-id = <0x9>;
};
clock@can2 {
allow_fractional_divider = <0x1>;
- allowed-parents = <0x121 0x5b 0x13a>;
+ allowed-parents = <0x121 0x5b 0x5e 0x13a>;
clk-id = <0xb>;
};
Used this command to flash this dtb file (note that we have a redundant setup, so we flash both slot A and slot B (suffix _b)):
$ sudo ./flash.sh -r -k bpmp-fw-dtb jetson-agx-xavier-devkit mmcblk0p1
$ sudo ./flash.sh -r -k bpmp-fw-dtb_b jetson-agx-xavier-devkit mmcblk0p1
After a reboot, verify that the proper dtb is loaded by checking /sys/kernel/debug/bpmp/debug/dt.
Next up, I modified kernel/dtb/tegra194-p2888-0001-p2822-0000.dtb:
--- kernel/dtb/tegra194-p2888-0001-p2822-0000.dts.bak 2021-04-19 13:33:34.342762489 +0200
+++ kernel/dtb/tegra194-p2888-0001-p2822-0000.dts 2021-04-19 13:34:32.248801134 +0200
@@ -5293,9 +5293,9 @@
reg = <0x0 0xc310000 0x0 0x400 0x0 0xc311000 0x0 0x32 0x0 0xc312000 0x0 0x1000>;
reg-names = "can-regs", "glue-regs", "msg-ram";
interrupts = <0x0 0x28 0x4>;
- pll_source = "osc";
- clocks = <0x4 0x11c 0x4 0xa 0x4 0x9 0x4 0x5b>;
- clock-names = "can_core", "can_host", "can", "osc";
+ pll_source = "pllaon";
+ clocks = <0x4 0x11c 0x4 0xa 0x4 0x9 0x4 0x5b 0x4 0x5e>;
+ clock-names = "can_core", "can_host", "can", "osc", "pllaon";
resets = <0x5 0x4>;
reset-names = "can";
mram-params = <0x0 0x10 0x10 0x20 0x0 0x0 0x10 0x10 0x10>;
@@ -5311,9 +5311,9 @@
reg = <0x0 0xc320000 0x0 0x400 0x0 0xc321000 0x0 0x32 0x0 0xc322000 0x0 0x1000>;
reg-names = "can-regs", "glue-regs", "msg-ram";
interrupts = <0x0 0x2a 0x4>;
- pll_source = "osc";
- clocks = <0x4 0x11d 0x4 0xc 0x4 0xb 0x4 0x5b>;
- clock-names = "can_core", "can_host", "can", "osc";
+ pll_source = "pllaon";
+ clocks = <0x4 0x11d 0x4 0xc 0x4 0xb 0x4 0x5b 0x4 0x5e>;
+ clock-names = "can_core", "can_host", "can", "osc", "pllaon";
resets = <0x5 0x5>;
reset-names = "can";
mram-params = <0x0 0x10 0x10 0x20 0x0 0x0 0x10 0x10 0x10>;
@@ -13576,7 +13576,7 @@
status = "okay";
disable {
- clocks = <0x14d 0x5e 0x4 0x9 0x4 0xb>;
+ clocks = < 0x4 0x9 0x4 0xb>;
};
};
And flash this device tree as well:
$ sudo ./flash.sh -r -k kernel-dtb jetson-agx-xavier-devkit mmcblk0p1
$ sudo ./flash.sh -r -k kernel-dtb_b jetson-agx-xavier-devkit mmcblk0p1
Verify the device tree is loaded by checking the proc file /proc/device-tree/mttcan@c310000/pll_source .
Note that for this to work, you do not need to modify and recompile the kernel.