MXC MMC driver and SDIO peripherals

[tommy tommy]

hi,sir!

1:your memory card test is fine,it can indicate sdhc data communicate ok
with sdio dma!
2:just use scope to test and know its clock,wifi clock is very strict,if
clock is lower ,will
get some issue.if sdio clock bigger than 25M or very slower,will get some
issue!
3:no relation with your MCU DMA,just SDIO DMA!

2009/10/22 Sascha Hauer <s.hauer at pengutronix.de>

> On Wed, Oct 21, 2009 at 10:51:56PM +0200, Daniel Mack wrote:
> > Hi Dan,
> >
> > On Wed, Oct 21, 2009 at 01:15:19PM -0700, Dan Williams wrote:
> > > On Wed, 2009-10-21 at 21:20 +0200, Daniel Mack wrote:
> > > > Hi,
> > > >
> > > > we're having trouble getting SDIO connected harware to fly on MX31
> based
> > > > designs. In particular, a SD8686 chip supported by the libertas_sdio
> > > > driver will hang forever when built without CONFIG_MMC_DEBUG=y. With
> > > > that option selected, however, the behaviour is a little different,
> and
> > > > I can at least see the following messages on a recent 2.6.32-rc5
> based
> > > > MX31 tree.
> > > >
> > > > Is there any common pitfall for such setups? I did more or less the
> same
> > > > thing on PXAs (same WLAN chip, same kind of interface, same
> firmware),
> > > > and haven't seen any such effects, so I suspect the MXC specific
> parts
> > > > to be the reason for that. Any ideas?
> > >
> > > Any idea what quirks your SDHC is using if any?  Does it require PIO or
> > > can it do DMA?
> >
> > In mainline kernels, DMA is limited to the MX2 SoC family. The MX3 that
> > I'm using is excluded from that feature, but I'mm not aware of the
> > reason for that.
>
> The reason is that the i.MX31/35/25 have a so called Smart DMA engine
> (SDMA). So far nobody has been smart enough to clean the Freescale code
> up for mainline. The original DMA engine this driver works with is
> equipped with the i.MX1/21/27 processors.
>
> Sascha
>
>
> --
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