i.MX ProcessorsのトピックRe: imx8mp-evk multicore M-core UART resource access failed

imx8mp-evk multicore M-core UART resource access failed

hjk003 — Wed, 26 Nov 2025 02:22:19 GMT

When using imx8mp-evk for heterogeneous communication, I attempted to call UART3 from the M core, but it failed. Below is my procedure.

1. Modify uboot device tree mcu_rdc. After compiling and generating falsh.bin, burn it.

2. Enter U-Boot and start the Linux system.

3. M-core code modified from demo.

The PC did not receive any data when the send function was called.

Re: imx8mp-evk multicore M-core UART resource access failed

Zhiming_Liu — Wed, 26 Nov 2025 05:53:19 GMT

Hi @hjk003

Please make sure you have replaced all UART4 to UART3, and below UART_INSTANCE.

Best Regards,
Zhiming

Re: imx8mp-evk multicore M-core UART resource access failed

hjk003 — Wed, 26 Nov 2025 06:32:28 GMT

@Zhiming_Liu Thanks for your reply. However, I don't want to change the default debug serial port; I want to use another UART3.

The left side contains my functions, and the right side contains the config used to set up the debug serial port.

Re: imx8mp-evk multicore M-core UART resource access failed

Zhiming_Liu — Wed, 26 Nov 2025 06:38:47 GMT

Hi @hjk003
Can you share your project here? or private message.

Best Regards,
Zhiming

Re: imx8mp-evk multicore M-core UART resource access failed

hjk003 — Wed, 26 Nov 2025 06:58:14 GMT

@Zhiming_Liu sure, This is my project.

Re: imx8mp-evk multicore M-core UART resource access failed

hjk003 — Wed, 26 Nov 2025 07:00:34 GMT

@Zhiming_Liu by the way, my project is based on demo changes made to evkmimx8mp_rpmsg_lite_pingpong_rtos_linux_remote_cm7.

Re: imx8mp-evk multicore M-core UART resource access failed

Zhiming_Liu — Wed, 26 Nov 2025 07:15:16 GMT

Hi @hjk003

请拷贝UART4的时钟配置代码，改成UART3。CLOCK_EnableClock(kCLOCK_Uart3)只能解除门控，不能设置对于的clock源和时钟速率。

Best Regards,
Zhiming

Re: imx8mp-evk multicore M-core UART resource access failed

hjk003 — Wed, 26 Nov 2025 07:40:20 GMT

@Zhiming_Liu

同样的设置时钟频率我也尝试过，但还是没有输出

Re: imx8mp-evk multicore M-core UART resource access failed

hjk003 — Wed, 26 Nov 2025 08:01:38 GMT

@Zhiming_Liu Hi, 另外我尝试将demo `evkmimx8mp_freertos_hello_cm7`中的log输出串口改为uart3, 但pc没有收到数据, ttl转uart串口我用两个串口rx->tx查看了没问题。
我的串口接的这三个脚

Re: imx8mp-evk multicore M-core UART resource access failed

Zhiming_Liu — Wed, 26 Nov 2025 08:19:30 GMT

Hi @hjk003

我这边之前是测试过的，一般确保uboot里M7独占UART3，SDK里只有复制UART4的代码就可以启动了。DbgConsole_Init里用的UART INSTANCE你改了吗？

Best Regards,
Zhiming

Re: imx8mp-evk multicore M-core UART resource access failed

hjk003 — Wed, 26 Nov 2025 09:14:06 GMT

@Zhiming_Liu uart的实例已经改成3了。还是不行。您方便提供一下修改过的demo吗。另外我这边用的是remoteproc启动的m7。A核和M核同在运行，需要改aft信任固件吗，还是只需要改uboot来做资源分配。

Re: imx8mp-evk multicore M-core UART resource access failed

hjk003 — Thu, 27 Nov 2025 02:37:57 GMT

@Zhiming_Liu

最后把kernel的设备树里的uart3 的pinctrl关掉就好了。但是我们更改了三个地方。
1. uart3 在 atf 里给A核、M核都有读写权限。
2. uboot里给了M核访问uart3的权限
3. kernel的rpmsg设备树里关掉了uart3的pinctrl 并且不起用uart3

我们的问题是：
1. 在remoteproc模式下 M核对外设的访问需要上面都做吗。感觉1，3是关键。2并不是。
2. 外设只能给M核或者A核吗。能不能都可以访问。如何操作。
3.A核、M核都配置管脚的电器属性会冲突？

Re: imx8mp-evk multicore M-core UART resource access failed

Zhiming_Liu — Thu, 27 Nov 2025 03:12:25 GMT

Hi @hjk003

1.首先关于RDC的配置，uboot里只分配给M7就行，这段配置会写在RAM中，ATF起来之后会读取这段配置，然后写入对应的寄存器。

2.关于这个共享访问的问题，我们建议将一组外设只分配给一个核心，例如你把GPIO2都分给M7，如果A53要访问的GPIO2下面的IO，需要通过rpmsg的机制来实现属性控制。其他外设类似。

3.设备树里的pinctrl并不会管UART 管脚分配给谁了，只要定义在里面，驱动就会设置对应的iomux寄存器。虽然M7和A53都有访问权限，但是后占有的就可能读写有问题。你可以试试在uboot里加载M7固件，看看是不是正常的，保留A53 设备树里的pinctrl设置。

Best Regards,
Zhiming

Re: imx8mp-evk multicore M-core UART resource access failed

hjk003 — Thu, 27 Nov 2025 04:01:46 GMT

@Zhiming_Liu 好的，感谢回复。我尝试一下。

Re: imx8mp-evk multicore M-core UART resource access failed

Zhiming_Liu — Thu, 27 Nov 2025 04:52:23 GMT

Hi,

基于rpmsg的共享访问可以参考SDK里的low_power_wakeword/app_srtm.c，例如i2c，内核里也有基于rpmsg的i2c驱动，例如设备树里的i2c_rpbus_3对应的驱动。

Best Regards,
Zhiming