Re: [PATCH 1/1] fsldma: ignore end of segments interrupt

On Thu, Feb 16, 2012 at 01:34:00PM -0600, Timur Tabi wrote:

Ira W. Snyder wrote:

quoted

This leads me to believe that this occurs mostly (but not always)
concurrent with the end-of-chain interrupt.

Have you tested this on an 85xx platform?

No. I don't have the ability to connect my P2020 up to an FPGA to
recreate the DMA workload that causes this on my 8349EA. I can run the
dmatest module, if you'd like.

I noticed something odd.  You're modifying fsldma_chan_irq(), which is for
DMA controllers that have per-channel IRQs.  83xx devices don't have
per-channel IRQs -- all channels on one controller have the same IRQ.
Looking at the device tree, I see that the IRQs are listed in the channel
nodes *and* in the controller node.  I don't see how we ever use the
per-controller ISR.

fsldma_ctrl_irq() (the per-controller irq handler) just calls through to
fsldma_chan_irq() (the per-channel irq handler).

I wonder if the shared IRQ is the part of the cause of the interrupts
you're seeing.

My device tree is slightly modified to remove the per-controller
interrupts and interrupt-parent properties. Each individual channel has
identical interrupts and interrupt-parent properties specified.

Someone here suggested that I do that, several years ago. It has been
too long, and I do not remember who. I can reverse it, and use the
per-controller IRQ instead.

quoted

In the last month, the "unhandled sr" error has occurred on 92 out of
120 boards in production use. The statistics are included below. On some
boards, it is much more frequent than on others. All boards have roughly
the same workload.

Another interesting tidbit from my logs: this only occurs on DMA channel
2 (the are numbered starting at 0, it is the 3rd channel). Here is an
example log message:

What happens if you never register that channel?  That is, remove this
node from the device tree:

dma-channel@100 {
	compatible = "fsl,mpc8349-dma-channel", "fsl,elo-dma-channel";
	reg = <0x100 0x80>;
	cell-index = <2>;
	interrupt-parent = <&ipic>;
	interrupts = <71 8>;
};

I can try that. I hunch the problem will move, as the carma-fpga driver
(see drivers/misc/carma/carma-fpga.c) will claim the 4th channel
instead.

Ira