Config of can device tree

Robotics & Edge Computing Jetson & Embedded Systems Jetson TX2
1

Hello, I encountered some problems when configuring the can device tree. I need your help. Thank you.
In the following settings, gpio_ can_ stb and gpio_ can_ en What are the functions of the two attributes?

mttcan@c310000 {
    status = "okay";
    gpio_can_stb = <&tegra_aon_gpio TEGRA_AON_GPIO(AA, 0) GPIO_ACTIVE_HIGH>;
    gpio_can_en = <&tegra_aon_gpio TEGRA_AON_GPIO(AA, 1) GPIO_ACTIVE_HIGH>;
};
 
mttcan@c320000 {
    status = "okay";
    gpio_can_stb = <&tegra_aon_gpio TEGRA_AON_GPIO(AA, 6) GPIO_ACTIVE_HIGH>;
    gpio_can_en = <&tegra_aon_gpio TEGRA_AON_GPIO(AA, 7) GPIO_ACTIVE_HIGH>;
};

In my circuit, CAN0_ STBY(E17)、CAN0_ ERR(E18)、CAN1_ STBY(C17)、CAN1_ ERR (C19) are all connected to DGND. In this case, do I need to set the device tree above to：

mttcan@c310000 {
    status = "okay";
    gpio_can_stb = <&tegra_aon_gpio TEGRA_AON_GPIO(AA, 0) GPIO_ACTIVE_LOW>;
    gpio_can_en = <&tegra_aon_gpio TEGRA_AON_GPIO(AA, 1) GPIO_ACTIVE_LOW>;
};
 
mttcan@c320000 {
    status = "okay";
    gpio_can_stb = <&tegra_aon_gpio TEGRA_AON_GPIO(AA, 6) GPIO_ACTIVE_LOW>;
    gpio_can_en = <&tegra_aon_gpio TEGRA_AON_GPIO(AA, 7) GPIO_ACTIVE_LOW>;
};
3

hello Yolomei,

it’s the device tree to configure default pin state, you may update those settings.
you may see-also Topic 63300 to enable and check CAN on TX2.
thanks

4

Still don’t understand. I found that no matter how I set these two attributes (high, low, or delete), they do not affect the use of the can bus.

mttcan@c310000 {
    status = "okay";
    gpio_can_stb = <&tegra_aon_gpio TEGRA_AON_GPIO(AA, 0) GPIO_ACTIVE_HIGH>;
    gpio_can_en = <&tegra_aon_gpio TEGRA_AON_GPIO(AA, 1) GPIO_ACTIVE_HIGH>;
};

mttcan@c310000 {
    status = "okay";
    gpio_can_stb = <&tegra_aon_gpio TEGRA_AON_GPIO(AA, 0) GPIO_ACTIVE_LOW>;
    gpio_can_en = <&tegra_aon_gpio TEGRA_AON_GPIO(AA, 1) GPIO_ACTIVE_LOW>;
};


mttcan@c310000 {
    status = "okay";
 //   gpio_can_stb = <&tegra_aon_gpio TEGRA_AON_GPIO(AA, 0) GPIO_ACTIVE_LOW>; 
//   gpio_can_en = <&tegra_aon_gpio TEGRA_AON_GPIO(AA, 1) GPIO_ACTIVE_LOW>;
};
5

hello Yolomei,

is the CAN interface up for the usage? may I know how you update the device tree?

6

After I finish setting in the device tree, use the following command to update the device tree:

sudo ./flash.sh -k kernel-dtb jetson-tx2 mmcblk0p1

After updating the device tree, use the following command to test：

candump can0 &
cansend can0 123#abcdabcd
7

hello Yolomei,

please also check below…
there’s cboot options for loading device tree via file system. it’s checking /boot/extlinux/extlinux.conf for the FDT entry, if that’s specified, it’ll prior to kernel-dtb partition for loading device tree blob.

8

I don’t quite understand what you mean. What I want to ask is, gpio_ can_ stb and gpio_ can_ en What are the functions of the two attributes? Why do my settings of these two attributes not affect the test results of the can bus

9

hello Yolomei,

so, please ensure you’ve update device tree correctly.

10

Each time, it is retested after successful flash. So, where can I see the describe of these two attributes

11

hello Yolomei,

is this driver has enabled?
it’s mttcan driver to parse device tree for these two properties.
for example,
$public_sources/kernel_src/kernel/nvidia/drivers/net/can/mttcan/native/m_ttcan_linux.c

static int mttcan_probe(struct platform_device *pdev)
{
        ...
        priv->gpio_can_en.gpio = of_get_named_gpio_flags(np, "gpio_can_en", 0, &flags);
        priv->gpio_can_stb.gpio = of_get_named_gpio_flags(np, "gpio_can_stb", 0, &flags);
12

Ok, thank you!
In the source code, the two attributes of these two nodes are the settings of the following soc pins:

image
image1121×140 9.68 KB

However, according to the OEM documentation, I should set the GPIO attribute of C19 C20 E18 C17 pin. As shown in the figure below:
image

Why is this?