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

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

[Jorge Ventura]

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

[Poddar, Sourav]

Hi,
[Sorry fot top posting]

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

________________________________________
From: linux-spi-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org [linux-spi-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org] on behalf of Jorge Ventura [jorge.araujo.ventura-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org]
Sent: Saturday, April 12, 2014 8:49 AM
To: linux-spi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Cc: jorge.araujo.ventura-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org
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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Re: spi-omap2-mcspi hangs when DMA and PIO are used simultaneously

[Jorge Ventura]

Sorry the delay.

I was using the Kernel 3.13.6 patched for beaglebone, where the patch
you suggested is needed but doesn't succeed. I decided to check the
mainline 3.14.0 and figured out that the patch is already applied. I
installed that one and repeated all tests to confirm the position of
problem in the source code. The problem is still exactly
the same as described in my first e-mail and the mcspi module is in the
instruction spi-omap2-mcspi.c:480 waiting for the callback function
completion.

The changes in the DMA_MIN_BYTES to force DMA or PIO only still works the
same way.

Thank you,
Ventura


On Sat, Apr 12, 2014 at 04:33:38AM +0000, Poddar, Sourav wrote:
> Hi,
> [Sorry fot top posting]
> 
> Can you try this patch?
> https://patchwork.kernel.org/patch/3511311/
> 
> ________________________________________
> From: linux-spi-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org [linux-spi-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org] on behalf of Jorge Ventura [jorge.araujo.ventura-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org]
> Sent: Saturday, April 12, 2014 8:49 AM
> To: linux-spi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
> Cc: jorge.araujo.ventura-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org
> 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.
> --
> To unsubscribe from this list: send the line "unsubscribe linux-spi" in
> the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
--
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Re: spi-omap2-mcspi hangs when DMA and PIO are used simultaneously

[Jorge Ventura]

This message is just to give a conclusion on my original post. This is a
description of some tests that I did to verify the drive
spi_omap2_mcspi related with the problem I reported. The conclusion is
that there is no problem with the driver.

I connected one beaglebone as the spi master to an Arduino uno as slave;
doing that I can have serial terminals at both sides so that I can see
everything. In the middle I have a logic analyzer to confirm that what I
am reading at the terminals is exactly what I can see in the display of
logic analyzer for both directions. I didn't find anything wrong!

Another check that I did was a stress test making transitions from PIO
to DMA and from DMA to PIO sending blocks of two different sizes and
again, everything works perfectly. This eliminates completely the drive
spi_opmp2_mcspi as the originator of the problem I am having with the
network card enc28j60. The problem has to be in the enc28j60 driver
itself.

Ventura

On Sat, Apr 12, 2014 at 04:33:38AM +0000, Poddar, Sourav wrote:
> Hi,
> [Sorry fot top posting]
> 
> Can you try this patch?
> https://patchwork.kernel.org/patch/3511311/
> 
> ________________________________________
> From: linux-spi-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org [linux-spi-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org] on behalf of Jorge Ventura [jorge.araujo.ventura-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org]
> Sent: Saturday, April 12, 2014 8:49 AM
> To: linux-spi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
> Cc: jorge.araujo.ventura-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org
> 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.
> --
> To unsubscribe from this list: send the line "unsubscribe linux-spi" in
> the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
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