Re: McSPI3 on the BeagleBoard

[Gregoire Gentil <gregoire@gentil.com>]

Philip,

Can you please post here or on the Beagleboard mailing list the u-boot
patch? This muxpin is very tricky and I have experienced many problems
when set up in the kernel while it seems to work better from u-boot -
don't know why,

Grégoire


On Wed, 2009-02-18 at 19:39 -0500, Philip Balister wrote:
> David Brownell wrote:
> > On Tuesday 17 February 2009, Philip Balister wrote:
> >> A number of people have tried using the McSPI3 interface with the spidev 
> >> driver. Running the spidev_test program shows data coming out of the 
> >> interface, but when we connect the SIMO to SOMI pins, the spidev_test 
> >> program shows only 0's. Someone tried wiring SOMI to +volts and still 
> >> only saw 0 read.
> > 
> > I took a quick glance, and the pinmuxing looks sort of OK if
> > you ignore the names ... use the right balls, not XXX:
> > 
> > +       AE2_3430_MCSPI3_CLK,
> > +       AG5_3430_MCSPI3_SIMO,
> > +       AH5_3430_MCSPI3_SOMI,
> > +       AF4_3430_MCSPI3_CS0,
> > +       AG4_3430_MCSPI3_CS1,
> > 
> > I suggest you start with a more focussed patch, only setting
> > up McSPI3.  For one thing, the MMC2 pinmuxing will interfere
> > with this set of MCSPI3 configurations.
> > 
> > Also, start with a less aggressive bit rate than 48 MHz; that
> > may be OK on a well designed board, but breadboards tend to
> > show flakiness at much over 10 MHz.
> 
> OK, more results:
> 
> 1) I do not intend for this to go into the kernel, well unless there is 
> an outcry from beagle users :)
> 
> 
> Steve Sakoman suggested I do the pinmux setup in u-boot and furnished me 
> with a small u-boot patch. Using this patch and removing the pinmux 
> stuff from the kernel patch lead to working spidev_test.
> 
> The 48 MHz is the max rate, spidev_test defaults to 500 kHz. (but it 
> appears to work at 48 MHz also.
> 
> Thanks for taking a look at this!
> 
> Philip
> 
> PS: I love photos: http://www.flickr.com/photos/32615155@N00/3291304854/

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