About dma_sync_single_for_{cpu,device}

On Tue, Jul 31, 2012 at 09:34:01AM +0200, Clemens Ladisch wrote:

Karl Beldan wrote:

quoted

On 7/31/12, Clemens Ladisch [off-list ref] wrote:

quoted

Karl Beldan wrote:

quoted

To tx a chunk of data from the SoC => network device, we :
- prepare a buffer with a leading header embedding a pattern,
- trigger the xfer and wait for an irq
// The device updates the pattern and then triggers an irq
- upon irq we check the pattern for the xfer completion

I was expecting the following to work:
	addr = dma_map_single(dev, buffer, size, DMA_TO_DEVICE);

Of both the CPU and the device write to the buffer, you must use
DMA_BIDIRECTIONAL.

This does not work (tested) :  seems to me BIDIRECTIONAL would just
add invalidate, and invalidate before the ram has been updated, as
stated, does not work.

Please show the exact sequence of dma_* calls, and also show when and
how the CPU and the device access the buffer.

Hmm, so I just spotted a line where we peek in the buffer after
invalidating .. cannot believe I missed it .. so sorry for the noise ..
now it's working.
I felt I would find the culprit right after posting ;)
Thanks Clemens !