Re: [PATCH] SPI: SSP SPI Controller driver

[Grant Likely <grant.likely-s3s/WqlpOiPyB63q8FvJNQ@public.gmane.org>]

On Tue, 11 Dec 2012 10:00:16 +0800, chao bi <chao.bi-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org> wrote:
> > > +static void dump_trailer(const struct device *dev, char *buf, int len, int sz)
> > > +{
> > > +	int tlen1 = (len < sz ? len : sz);
> > > +	int tlen2 =  ((len - sz) > sz) ? sz : (len - sz);
> > > +	unsigned char *p;
> > > +	static char msg[MAX_SPI_TRANSFER_SIZE];
> > 
> > Is this size a limitation of the hardware, of of the driver?
> 
> I think this size is attributed to the DMA controller's maximum block size. 
> On Medfield platform, the DMA controller used by SSP SPI has defined its maximum 
> block size and word width, so SPI transfer size should not exceed the maximum size that 
> DMA could transfer in one block.

Typically what a driver should do here is to split up the transfer into
multiple DMA operations. I won't nack the driver over this issue, but
the driver should not have a maximum transfer size limitation in this
way.

g.


------------------------------------------------------------------------------
LogMeIn Rescue: Anywhere, Anytime Remote support for IT. Free Trial
Remotely access PCs and mobile devices and provide instant support
Improve your efficiency, and focus on delivering more value-add services
Discover what IT Professionals Know. Rescue delivers
http://p.sf.net/sfu/logmein_12329d2d