Re: [PATCH 4/5] mmc: mxcmmc: enable DMA support on mpc512x

Anatolij Gustschin
2013-03-14T21:18:18Z

On Thu, 14 Mar 2013 21:11:39 +0100
Sascha Hauer <s.hauer@pengutronix.de> wrote:

> On Thu, Mar 14, 2013 at 05:40:53PM +0100, Anatolij Gustschin wrote:
> > Add SDHC DMA channel description to the mpc512x device
> > tree to enable slave channel requesting in the mxcmmc
> > driver.
> >
> > mpc512x DMA engine doesn't support endianness conversion
> > when reading/writing data from peripheral's FIFO, so we
> > have to swap data buffers before each DMA write and after
> > each DMA read transfer manually.
> >
> > Since chained SDHC DMA transfers are not supported on
> > mpc512x, limit 'max_segs' tunable parameter to one and
> > initialise it to 64 only when running on i.MX platforms.
>
> They are also not supported on the older i.MX platforms. Shouldn't this
> be handled in the DMA driver?

This could be handled in the DMA driver, but up to now nobody
cared to extend the DMA driver so.

Anatolij