RE: spi-omap2-mcspi hangs when DMA and PIO are used simultaneously

["Poddar, Sourav" <sourav.poddar@xxxxxx>]

Hi,
[Sorry fot top posting]

Can you try this patch?
https://patchwork.kernel.org/patch/3511311/

________________________________________
From: linux-spi-owner@xxxxxxxxxxxxxxx [linux-spi-owner@xxxxxxxxxxxxxxx] on behalf of Jorge Ventura [jorge.araujo.ventura@xxxxxxxxx]
Sent: Saturday, April 12, 2014 8:49 AM
To: linux-spi@xxxxxxxxxxxxxxx
Cc: jorge.araujo.ventura@xxxxxxxxx
Subject: spi-omap2-mcspi hangs when DMA and PIO are used simultaneously

I am struggling with this problem for several weeks with no success.

I am using spi-omap2-mcspi to drive a network card based on enc28j60 and everything works perfect if I define
DMA_MIN_BYTES = 0 (force to use DMA only) or DMA_MIN_BYTES = 99999 (force to use PIO only).
But if I use the original value of 160, the board can send out 10 to 20 pings approximately
and if for any reason the drive switch from PIO to DMA what will be decided by the size of data,
some workqueue tasks hung and the card stops.

I am running with "lockdep" and "detect hung tasks" and I can see that four tasks are stopped,
three from enc28j60 and one from spi-omap2-mcspi.

The mcspi is stopped in spi-omap2.mcspi.c:480 to wait the completion of omap2_mcspi_rx_callback
that it never happens.

   468                 if (tx) {
   469                         tx->callback = omap2_mcspi_rx_callback;
   470                         tx->callback_param = spi;
   471                         dmaengine_submit(tx);
   472                 } else {
   473                                 /* FIXME: fall back to PIO? */
   474                 }
   475         }
   476
   477         dma_async_issue_pending(mcspi_dma->dma_rx);
   478         omap2_mcspi_set_dma_req(spi, 1, 1);
   479
   480         wait_for_completion(&mcspi_dma->dma_rx_completion);
   481         dma_unmap_single(mcspi->dev, xfer->rx_dma, count,
   482                          DMA_FROM_DEVICE);

Any help/suggestion is welcome. Need more information, please let me know, I have much
more details.

Thank you.
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