On 10/31/2010 3:29 PM, Ming Lei wrote:
2010/10/31 Anand Gadiyar<gadiyar@xxxxxx>:
The Inventra DMA engine in version 1.8 and later of the MUSB
controller cannot handle DMA addresses that are not aligned
to a 4 byte boundary. It ends up ignoring the last two bits
programmed in the DMA_ADDR register. This is a deliberate
design change in the controller and is documented in the
programming guide.
Earlier versions of the controller could handle these
accesses just fine.
Fail dma_channel_program if we see an unaligned address when
using the newer controllers, so that the caller can carry out
the transfer using PIO mode.
(Current callers already have this backup path in place).
Signed-off-by: Anand Gadiyar<gadiyar@xxxxxx>
Cc: Felipe Balbi<balbi@xxxxxx>
Cc: Ming Lei<tom.leiming@xxxxxxxxx>
Cc: Ajay Kumar Gupta<ajay.gupta@xxxxxx>
Cc: Mike Frysinger<vapier@xxxxxxxxxx>
Tested-by: Ming Lei<tom.leiming@xxxxxxxxx>
This patch is verified OK about g_ether function on beagle xM board,
but the revised patch "usb: musb: gadget: Unmapping the dma buffer
when switching to PIO mode" [1] should be applied first.
---
Patch based on linux-next as of 20101029.
I believe Blackfin is also affected by this, but I'm not sure how
they're working around this. Mike?
MUSB on Blackfin will fallback to PIO too, so no any working around
for it, right?
I meant Blackfin should also have hit this issue so far. I'm making
a change based on the MUSB revision - so this change will affect
Blackfin for sure - they use revision 1.9 and 2.0 I think. So I'm just
wondering if they really are affected, or they've simply never hit this
scenario before.
- Anand
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