On Wed, Jun 29, 2011 at 10:00:39PM +0800, Shawn Guo wrote:

On Wed, Jun 29, 2011 at 02:29:42PM +0200, Wolfram Sang wrote:

quoted

quoted

quoted

Still, the problem exists: When a second channel GPMI channel is
requested, dmaengine will return -EBUSY, because the DMAIRQ is already
taken.

Yes, we should change the DMA code, it is a DMA bug.
I ever submitted a patch about the issue:
http://patchwork.ozlabs.org/patch/87145/

That approach was rejected because it would register the same handler
n-times where one time would do. Your other approach puts too much
mach-specific details into the driver IMO and probably won't scale very
well. Maybe we should add something to the private dma_data (like flags
indicating SHARED) and then do some refcounting?

I would suggest leave this gpmi specific quirk to gpmi driver to sort
out.  With the following mxs-dma change, it should work if gpmi driver
can pass the valid gpmi irq number for only one gpmi channel, and -1
for all others.

...which brings us right into the 'NO_IRQ is 0' discussion :)

Other than that, [thinking loud] this will help if all irq-sharing
channels are handled by the same driver. If not, we would just add
IRQF_SHARED (hopefully this will never be needed). Yup, sounds
reasonable to me. Will give it a second thought later, though.

-- 
Pengutronix e.K.                           | Wolfram Sang                |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
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