topic imx6q Uart receive data error "RX FIFO overrun" in i.MX Processors

imx6q Uart receive data error "RX FIFO overrun"

1282497337 — Sat, 16 Mar 2019 09:33:04 GMT

Hi,community

We use imx6q UART port to communicate and receive information from other device using RS485,The device will always send data, we have configured ttymxc3 to work at 576000 ,then I used imx6 UART to receive the data, when device always connect to the imx6 UART, it's can receive data well.

but when I cut it down afterwards link it again, I will got the error message from kernel

imx-uart 21f0000.serial: Rx FIFO overrun
imx-uart 21f0000.serial: Rx FIFO overrun
imx-uart 21f0000.serial: Rx FIFO overrun
imx-uart 21f0000.serial: Rx FIFO overrun
...........................

Once I got the error I cannot receive data anymore,unless kill the application and open it again.

I used the Oscilloscope to measure the UART port (near the imx6 chip )waveform there is no problem , I got the signal and the signal is okey. we test all UART port and the error it's same !

We have using 3.14.52 kernel,the board is imx6q-sabresd

Really appreciate any help!

Thanks very much

Alee

Re: imx6q Uart receive data error "RX FIFO overrun"

igorpadykov — Sun, 17 Mar 2019 22:39:54 GMT

Hi AL

one can try to reset uart using sect.64.10.2 Software reset i.MX6DQ Reference
Manual and if sdma was used, try to not use sdma.
https://www.nxp.com/docs/en/reference-manual/IMX6DQRM.pdf

Best regards
igor
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Re: imx6q Uart receive data error "RX FIFO overrun"

1282497337 — Mon, 18 Mar 2019 09:07:32 GMT

Hi igor

As you know I used the sdma to transmit data,then for test i disable sdma and it can solve such problem (if i got FIFO overrun UART will continue receive data), unfortunately another peoblem arises that when I send data about 10000 Byte pre second use baud rate 115200 ,thread kworker occupy CPU about 15 present, I used baud rate 115200 * 10 and send data about 500000 Byte/sec kworker occupy CPU over 85%. its cause many other problem ,

Could you give me some advise if i want to use sdma how to solve the problem that fifo overrun and cannot receive data anymore .

Looking forward to your suggestions!

thanks

ALee

Re: imx6q Uart receive data error "RX FIFO overrun"

1282497337 — Wed, 20 Mar 2019 06:24:17 GMT

Hi community

maybe I addressed this problem,but not sure.Blowe is my solution:

I'm using kernel 3.14.52 and I found the source code kernel/driver/tty/serial/imx.c will got the DMA transmit status but do not deal with it.

Imx.c (drivers\tty\serial)
static void dma_rx_callback(void *data)
{
struct imx_port *sport = data;
struct dma_chan *chan = sport->dma_chan_rx;
  struct tty_struct *tty = sport->port.state->port.tty;
  struct dma_tx_state state;
  enum dma_status status;
  unsigned int count;
  /* If we have finish the reading. we will not accept any more data. */
  if (tty->closing) {
      imx_rx_dma_done(sport);
      return;
  }
  status = dmaengine_tx_status(chan, (dma_cookie_t)0, &state); // to get DMA status but not care this return value "status"?
+        if(DMA_ERROR == status){
+               dmaengine_terminate_all(chan);
+               dmaengine_resume(chan);
+         }
  count = RX_BUF_SIZE - state.residue;
  sport->rx_buf.buf_info[sport->rx_buf.cur_idx].filled = true;
  sport->rx_buf.buf_info[sport->rx_buf.cur_idx].rx_bytes = count;
  sport->rx_buf.cur_idx++;
  sport->rx_buf.cur_idx %= IMX_RXBD_NUM;
  dev_dbg(sport->port.dev, "We get %d bytes.\n", count);
  if (sport->rx_buf.cur_idx == sport->rx_buf.last_completed_idx)
      dev_err(sport->port.dev, "overwrite!\n");
  if (count)
      dma_rx_work(sport);
}
The DMA status defined
Dmaengine.h (include\linux)
enum dma_status {
DMA_COMPLETE,
DMA_IN_PROGRESS,
DMA_PAUSED,
DMA_ERROR,
};

Under normal circumstances this "status == 1" this mean is DMA_IN_PROGRESS ,but sometimes I will got "status == 3", the DMA error occurred . then i can't receive data from this serial port anymore unless I closs this uart and open it again.

now it's will continue receive data when i get "status == 3" DMA error .