[PATCH] Device Tree binding for the 'mv_xor' XOR engine DMA driver

[Andrew Lunn]

On Thu, Nov 15, 2012 at 06:20:05PM +0100, Thomas Petazzoni wrote:
> Hello,
> 
> This patch set adds a Device Tree binding for the Marvell XOR engine
> driver, which allows to support these XOR engines in the Armada 370
> and Armada XP SoCs.

Hi Thomas

I tested on kirkwood, both old style and DT. I tested using the
dmatest kernel module. That shows up an old issue, pre-dating your
patchset. It dmatest dereferences a NULL pointer during cleanup, due
to a missing function in the driver. I will submit a patch for this
soon.

The dmatest shows up a second issue:

root at qnap:~# insmod ./dmatest.ko iterations=100
dmatest: Started 2 threads using dma0chan0
dmatest: Started 2 threads using dma1chan0
dmatest: Started 2 threads using dma2chan0
dmatest: Started 2 threads using dma3chan0
dma3chan0-xor0: #3: prep error with src_off=0x13c2 dst_off=0x2c7c len=0x5d
dma1chan0-copy0: #16: prep error with src_off=0x1f50 dst_off=0x904 len=0x33
dma3chan0-copy0: #22: prep error with src_off=0x14c2 dst_off=0x389b len=0x6f
dma0chan0-copy0: #31: prep error with src_off=0x10b6 dst_off=0x323c len=0x2f
dma3chan0-copy0: #49: prep error with src_off=0x17b5 dst_off=0x3eca len=0x29

The driver refuses any operation where the buffer is less than 128
bytes. The datasheet for Kirkwood says the buffer length must be 8
bytes or more. So maybe we should reduce this 128 limit down to 8?

But is the driver allowed to refuse small copies? Is the caller
expected to fall back to software? Does the dma core implement this
fallback? Lots of questions i don't know the answers to.

Anyway, you can add a 

Tested-by: Andrew Lunn <andrew at lunn.ch>

since with your patches it works just as well as before your patches.

      Andrew