On Tuesday 26 April 2005 05:20 pm, Phil Blundell wrote:
> On Tue, 2005-04-26 at 15:41 -0700, Matthew Reimer wrote:
> > 1. Set up PXA DMA to copy from SDIDATA.
> >
> > 2. Set up [SH]AMCOP's SD registers.
> >
> > 3. Set the interrupt controller's DREQEN bit which would then trigger the
> > PXA DMA to copy directly from SDIDATA.
> >
> > 4. Repeat steps 1-3 for every SD transfer.
>
> I don't exactly understand how the handshaking between the SD controller
> and the DMA block would work in this case. If the DREQ bit in the IC is
> permanently set then, as soon as you set DREQEN, the pxa255 will
> immediately start sucking data out of SDIDATA without actually waiting
> for data to be available. I think what you really need is to bring out
> the SDI's DREQ onto HAMCOP DREQ directly, but that doesn't seem to be
> possible.
Yeah, it would be nice and tidy to have SDI's DREQ go right to PXA.
Couldn't we just watch SDIDSTA[RxDatOn] or SDIFSTA[RFDET] or SDIFSTA[RFHalf],
and when data starts flowing into the FIFO, then we set DREQEN? It's
basically software-controlled DREQ.
Yes, it's ugly, but maybe it would be faster.
Matt
Received on Tue Apr 26 2005 - 19:31:44 EDT
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