topic Re: EDMA cannot be aborted anymore in i.MX RT Crossover MCUs

EDMA cannot be aborted anymore

benedek_kupper — Tue, 25 Aug 2020 14:20:18 GMT

There's a new bug introduced in the 2.8.2 SDK for iMX RT1010, in EDMA_SubmitTransfer(). The function now also checks if the TCD's CITER != BITER, which actually will be the case if the EDMA_AbortTransfer() is called while the transfer is active. This will result in EDMA_SubmitTransfer() to return busy, preventing the restart of the EDMA transfer, contradicting the statement at EDMA_AbortTransfer: "Users can submit another transfer after calling this API."

The details of the new busy condition:

        /*
         *    Check if EDMA channel is busy:
         *    1. if channel active bit is set, it implies that minor loop is executing, then channel is busy
         *    2. if channel active bit is not set and BITER not equal to CITER, it implies that major loop is executing,
         * then channel is busy
         *
         *    There is one case can not be covered in below condition:
         *    When transfer request is submitted, but no request from peripheral, that is to say channel sevice doesn't
         *    begin, if application would like to submit another transfer , then the TCD will be overwritten, since the
         *    ACTIVE is 0 and BITER = CITER, for such case, it is a scatter gather(link TCD) case actually, so
         *    application should enabled TCD pool for dynamic scatter gather mode by calling EDMA_InstallTCDMemory.
         */
        if (((handle->base->TCD[handle->channel].CSR & DMA_CSR_ACTIVE_MASK) != 0U) ||
            (((handle->base->TCD[handle->channel].CITER_ELINKNO & DMA_CITER_ELINKNO_CITER_MASK) !=
              (handle->base->TCD[handle->channel].BITER_ELINKNO & DMA_BITER_ELINKNO_BITER_MASK))))
        {
            return kStatus_EDMA_Busy;
        }

Re: EDMA cannot be aborted anymore

jeremyzhou — Tue, 25 Aug 2020 23:47:17 GMT

Hi Benedek Kupper,

Thank you for your interest in NXP Semiconductor products and
for the opportunity to serve you.
I'll check it soon.

Have a great day,
TIC

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Re: EDMA cannot be aborted anymore

jeremyzhou — Wed, 02 Sep 2020 06:53:07 GMT

Hi Benedek,

Sorry for the reply late.
I don't think call EDMA_SubmitTransfer() after the EDMA_Abort Transfer() function, then it will result in EDMA_SubmitTransfer() to return busy. as the CSR register will be cleared in the EDMA_Abort Transfer() as below shows.2020-09-02_14-51-57.png

Have a great day,
TIC

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Re: EDMA cannot be aborted anymore

benedek_kupper — Wed, 02 Sep 2020 10:00:29 GMT

Here's how to reproduce the issue:

Import the evkmimxrt1010 lpuart_edma_transfer example, using SDK version 2.8.2
Apply the following patch (the code between TEST BEGIN and TEST END) to the main function (this is showing my use case)
Press a button on the debug console so that the MCU receives a byte of UART data

while (1) { /* If RX is idle and g_rxBuffer is empty, start to read data to g_rxBuffer. */ if ((!rxOnGoing) && rxBufferEmpty) { rxOnGoing = true; LPUART_ReceiveEDMA(DEMO_LPUART, &g_lpuartEdmaHandle, &receiveXfer); } // TEST BEGIN { lpuart_transfer_t received = receiveXfer; LPUART_EnableRxDMA(DEMO_LPUART, 0); // ensure no DMA data is cached __DSB(); int status = LPUART_TransferGetReceiveCountEDMA(DEMO_LPUART, &g_lpuartEdmaHandle, (uint32_t*)&received.dataSize); if (status == kStatus_NoTransferInProgress) { // if the transfer is complete, the length isn't modified // transferred.dataSize = mEdma.rxDataSizeAll; } if (received.dataSize == 0) { // nothing was received, just re-enable feeding DMA LPUART_EnableRxDMA(DEMO_LPUART, 1); } else { // need to abort current transfer before starting a new one LPUART_TransferAbortReceiveEDMA(DEMO_LPUART, &g_lpuartEdmaHandle); // switch to other buffer LPUART_ReceiveEDMA(DEMO_LPUART, &g_lpuartEdmaHandle, &receiveXfer); } } // TEST END /* If TX is idle and g_txBuffer is full, start to send data. */ if ((!txOnGoing) && txBufferFull) { txOnGoing = true; LPUART_SendEDMA(DEMO_LPUART, &g_lpuartEdmaHandle, &sendXfer); } /* If g_txBuffer is empty and g_rxBuffer is full, copy g_rxBuffer to g_txBuffer. */ if ((!rxBufferEmpty) && (!txBufferFull)) { memcpy(g_txBuffer, g_rxBuffer, ECHO_BUFFER_LENGTH); rxBufferEmpty = true; txBufferFull = true; } }

The result is:

The abort and restart is unsuccessful, which leads to the same byte being reported as received, and no further data reception is happening.

Re: EDMA cannot be aborted anymore

jeremyzhou — Wed, 09 Sep 2020 07:43:03 GMT

Hi，
I‘ve basically replicated your phenomenon, and I'll report this phenomenon in the next round of the Filed Trial of the SDK library.
Have a great day,
TIC

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Re: EDMA cannot be aborted anymore

jmjm — Tue, 12 Mar 2024 02:21:42 GMT

Hi Jeremy, do we have any update on this issue, I faced the same thing and I think the issue from this

jmjm_0-1710209979261.png

back in old days, the checking is different

jmjm_1-1710210060959.png

Re: EDMA cannot be aborted anymore

srinivas_chilaka — Fri, 15 Mar 2024 04:21:20 GMT

"Comparing the driver versions, I do think that the change to EDMA_SubmitTransfer() checking for CITER != BITER makes sense, but I see how that cause an issue when there is an aborted transfer. I think the correct fix is to change the EMDA_AbortTransfer function so that it clears BITER and CITER along with the CSR. This will prevent an aborted transfer from looking like a major loop in progress to the submit transfer function."

srinivas_chilaka_0-1710476461799.png

Re: EDMA cannot be aborted anymore

jmjm — Fri, 15 Mar 2024 06:09:23 GMT

Hi @srinivas_chilaka

Thanks for the quick response, I do think that by resetting CITER and BITER could solve the issue

Let me test out the changes and get back to you