Why is uart0 blocking uart1 ?

[IYetk]

Hello,

I am running example "OpenAMP_TTY_echo" on the board "stm32mp157c-dk2"

I have modified the code a little bit so that channel0 (uart0) doesn't have to wait for a massage from linux side and transmit message every half second. It is sending the messages on every half second without problem.But the problem is now uart1 is not working. I mean on linux side if I write "echo "Hello Virtual UART1" >/dev/ttyRPMSG1" , I can not receive any callback message from the console. This means channel 1 is not working because channel 0 is blocking it. Is it normal ? Why normal ?

while (1)
  {
 
      OPENAMP_check_for_message();
       " "
       " "
      VIRT_UART_Transmit(&huart0, Data, size);
      HAL_Delay(500);
 
      if (VirtUart1RxMsg) {
        VirtUart1RxMsg = RESET;
        VIRT_UART_Transmit(&huart1, VirtUart1ChannelBuffRx, VirtUart1ChannelRxSize);
      }
 
  }

[Calvin Ageneau · Accepted solution]

Hello,

I managed to reproduce and i found an issue in the MAILBOX_Poll function in OpenAPM_TTY_echo/Src/mbox_ipcc.c.

This function treats either a buffer free or a new message event but not both. As a buffer free event is received each time a rpmsg is sent from Cortex-M4, the message received event is never considered and the variable is never set. It will be fixed in a future version but if you want to fix it in your code you can replace the MAILBOX_Poll function by this one : 

/**
  * @brief  Initialize MAILBOX with IPCC peripheral
  * @param  virtio device
  * @retval : Operation result
  */
int MAILBOX_Poll(struct virtio_device *vdev)
{
  /* If we got an interrupt, ask for the corresponding virtqueue processing */
	int ret = -1;
  if (msg_received_ch1 == RX_BUF_FREE) {
    OPENAMP_log_dbg("Running virt0 (ch_1 buf free)\r\n");
    rproc_virtio_notified(vdev, VRING0_ID);
    msg_received_ch1 = RX_NO_MSG;
    ret = 0;
  }
 
  if (msg_received_ch2 == RX_NEW_MSG) {
    OPENAMP_log_dbg("Running virt1 (ch_2 new msg)\r\n");
    rproc_virtio_notified(vdev, VRING1_ID);
    msg_received_ch2 = RX_NO_MSG;
 
    /* The OpenAMP framework does not notify for free buf: do it here */
      rproc_virtio_notified(NULL, VRING1_ID);
    ret = 0;
  }
 
  return ret;
}

BR,

Calvin

[IYetk]

Thank you very much