Hi Mike,
On Sat, Oct 09, 2010 at 18:25:54, Michael Williamson wrote:
> On 10/08/2010 03:22 PM, Michael Williamson wrote:
> > On 10/6/2010 11:37 AM, Nori, Sekhar wrote:
> >> On Mon, Sep 20, 2010 at 23:12:53, Michael Williamson wrote:
> >>
> >> I just finished pushing the DMA related patches to the git branch[1].
> >> I have not tested yet, but feel free to give it a go (maybe I will get
> >> lucky again!).
> >>
> >
> >
> > I gave it a go for our platform. The good news is, polled and interrupt
> > driven mode still work!
> > The bad news is that DMA mode hangs up the kernel on the first read
> > attempt, stalled waiting
> > for the transfer completion notification (hmmm.... I think this was a spot
> > where things were
> > tweaked a bit? :) )
> >
> > I'll see if I can narrow it down some more if you don't get to it first.
> >
>
> I think I found it. This patch (below, and on [2]) got it working for me.
> The Rx DMA
> size on transfer requests with no receive buffer provided needs to match the
> requested
> size (and the transmit size), not the size of the temporary buffer. All good
> as the
> DMA address increment is 0 in this case.
>
> I'll try to do some more testing next week, but so far so good.
Sorry, I couldn’t get to testing even today. Should be on it
tomorrow.
>
> ---
> diff --git a/drivers/spi/davinci_spi.c b/drivers/spi/davinci_spi.c
> index 662ebbe..8206df1 100755
> --- a/drivers/spi/davinci_spi.c
> +++ b/drivers/spi/davinci_spi.c
> @@ -632,13 +632,11 @@ static int davinci_spi_bufs(struct spi_device *spi,
> struct spi_transfer *t)
> * source address never increments.
> */
>
> - if (t->rx_buf) {
> + rx_buf_count = davinci_spi->rcount;
> + if (t->rx_buf)
> rx_buf = t->rx_buf;
> - rx_buf_count = davinci_spi->rcount;
> - } else {
> + else
> rx_buf = davinci_spi->rx_tmp_buf;
> - rx_buf_count = sizeof(davinci_spi->rx_tmp_buf);
> - }
>
> t->rx_dma = dma_map_single(&spi->dev, rx_buf, rx_buf_count,
> DMA_FROM_DEVICE);
Hmm, looks like the Tx and Rx DMA must always run for the same duration. I was
under the impression Tx is required to keep the clock running, and so must
always
run for the length of transfer requested, but Rx DMA can finish earlier.
I guess replacing the line:
param.a_b_cnt = rx_buf_count << 16 | data_type;
with
param.a_b_cnt = davinci_spi->rcount << 16 | data_type;
will also fix the issue?
>
> >
> >> Also, do you have patches adding SPI support for DA850 platform?
> >> I can include these patches on this branch so others who will be
> >> testing dont have to repeat the work.
> >>
> >
> >
> > I cloned your repository at [1] and published the additions needed to made
> > to test it on the
> > mitydsp-l138 platform (da850 based) at [2] (never mind the UART one at the
> > end). I had to add
> > clock support for the spi devices and define the platform SPI
> > resources/registration routines.
> > I'd appreciate a quick peek at those to make sure that I didn't make any
> > errors. The spi
> > registration may be refactorable (sp?) to support da830, I didn't look to
> > closely at that.
> >
> > If any of it is usable, great.
Sure it is! I checked-in your patches with some modifications to my
branch. The most notable change being usage of da8xx instead of da850 since
the same code should work on da830 as well. Apart from this there are
some cosmetic changes (patches squashed, some non-relevant hunks dropped
etc). Do update the patches in your tree if you are OK with the changes.
Thanks,
Sekhar
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