dmaengine pl08x dt crash

[Linus Walleij]

On Wed, Mar 23, 2016 at 4:40 PM, Johannes Stezenbach <js at sig21.net> wrote:

> I'm trying to use the new devicetree support for pl08x
> added in commit aa4734da667442
> (dmaengine: pl08x: support dt channel assignment).
>
> It causes crash in the pl011 serial driver when it calls
> dma_chan_name() because the dma_chan->dev->device is NULL.
> I think the reason is dma_async_device_register() is called
> during pl08x_probe(), but at this time the number of slave
> channels is still 0 as these get allocated later in
> pl08x_of_xlate() when clients request the channels.
>
> [    0.420835] pl08xdmac dma8ch0: initialized 8 virtual memcpy channels
> [    0.427380] pl08xdmac dma8ch0: initialized 0 virtual slave channels
> [    0.436185] pl08xdmac dma8ch0: DMA: PL080s rev1 at 0xfec00000 irq 8

So you are trying to use it on the Samsung S3C?

I have it working on the Nomadik, but for platforms with fixed signal
assignement I had to apply these patches:
https://git.kernel.org/cgit/linux/kernel/git/linusw/linux-nomadik.git/log/?h=pl08x-dma

dma: pl08x: support fixed signal assignment
dma: pl08x: allocate OF slave channel data at probe time

And the example:
ARM: nomadik: add DMA engine and some channelspl08x-dma

I have meant to follow up on it but haven't gotten around to.

If the Samsung also has fixed channels (no mux in front of the
DMA lines) I think this might be what you need. They are not
yet merged because Joachim reported a crash with the second
patch and I haven't yet figured out why.

Yours,
Linus Walleij