On Thu, May 30, 2013 at 11:19:33PM +0200, Linus Walleij wrote:
> On Thu, May 30, 2013 at 10:31 PM, Tony Lindgren <tony@xxxxxxxxxxx> wrote:
>
> > There are many devices where the device FIFO is memory mapped to the
> > GPMC bus on omaps, like TUSB, OneNAND, smc911x etc. I believe the
> > only reason why these have not been converted to the dmaengine is
> > the fact that dmaengine cannot configure the DMA hardware to do
> > autoincrement and loop over the device FIFO.
>
> OK that seems like something pretty generic that we could just add
> to the struct dma_slave_config actually, something like:
>
> u32 src_fifoloop;
> u32 dst_fifoloop;
Yes for genric but not for loop. For most of our cases we are considering the
FIFO address as a constant. Typically DMA controllers have this ability to
perform incremental/decremental/constant FIFO address.
What would make sense to have is:
enum dmaengine_slave_addr_mode {
DMAENGINE_SLAVE_ADDR_CONSTANT = 0,
DMAENGINE_SLAVE_ADDR_INCREMANT,
DMAENGINE_SLAVE_ADDR_DECREMENT,
};
and add these to struct dma_slave_config:
enum dmaengine_slave_addr_mode src_mode;
enum dmaengine_slave_addr_mode dstn_mode;
For loopover we can have:
u32 loop_counter;
on 0 means no loop, and valid value tells when to loopover (offset).
will this help for all of the above controllers and their conversion?
> Given in # of words on the src/dst address simply, left as zero
> for hitting a constant address over and over again.
>
> We'd need both to make space for device->device transfers.
>
> If this is all that is needed to convert them do DMAengine
> I'd surely ACK it (FWIW).
--
~Vinod
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