nRF9160 non-secure firmware image can access UARTE2 secure peripheral

[Siddharth Kachhia]

Hi, I'm working on nRF9160 modem firmware update.

For Understanding SPM with secure and non-secure firmaware, I have used UARTE2(secure peripheral) into non-secure firmware image. Though UARTE2is secure it can be accessed through non-secure board image.

How is secure peripheral(NRF_UARTE2) can be accessed by non-secure board image ?

Image is attached for reference. It goes to init UART2 which is connected with nRF52840 mounted on nRF9160 board and it succeed without any error.

[Sigurd Hellesvik]

Hi Siddharth

I will have a look at this and return with more information on Monday.

Regards,
Sigurd Hellesvik

[Sigurd Hellesvik]

Hi

Could you post the code you used to enable and initialize the UARTE2?

Regards,
Sigurd Hellesvik

[Siddharth Kachhia]

Code used to initialize the UARTE2 for UART communication between nRF9160 and nRF52840:

<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< 

  if (enabled_transport & UART_COMM_TRANS)
{
memset(&uart_ctx, 0x00, sizeof(uart_ctx));
printk("UART 9160 start!\n");
err = uart_comm_init(DT_LABEL(DT_NODELABEL(uart2)), &uart_ctx, ASYNC_UART_COMM);
if (err != 0)
{
printk("Fail to init UART\n");
break;
}
}

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

This code is working fine with CONFIG_TRUSTED_EXECUTION_NONSECURE=y and CONFIG_SPM_NRF_UARTE2_NS=n config.

As UARTE2 is configured as secure peripheral, it would provide an error with non-secure(ns) build. But it is not producing error related to security attribute. Reason ?

[Sigurd Hellesvik]

Hi

If you set CONFIG_SPM_NRF_TWIM2_NS=n (in <project_folder>/child_image/spm.conf), this should make UARTE2 Secure as well.-

UARTE2 shares peripheral ID with TWIM2, see Instantiation.
My guess is that when TWIM is conigured as Non-Secure, this sets the whole of Peripheral ID 10 to Non-Secure as well,
but we will have to investigate this further.

If the work-around does not work for you, let me know.

Regards,
Sigurd Hellesvik