[U-Boot] AM335x SPI boot not working

[Tom Rini]

On Mon, Jan 18, 2016 at 10:02:32AM +0100, Lars Poeschel wrote:
> Am Donnerstag, 14. Januar 2016, 16:01:00 schrieben Sie:
> > On Wed, Dec 16, 2015 at 03:34:24PM +0100, Lars Poeschel wrote:
> > > Hi!
> > > 
> > > I played a bit with spi boot on my am3359. It is currently not working
> > > with u- boot at least with the machine I work here. Has anyone else
> > > problems with spi boot on am335x ?
> > > 
> > > On boot SPL reads a value from a processor register to determine from
> > > which
> > > device it was booting and it uses that value to continue booting process
> > > from that same device.
> > > I found, that in my case the processor register contained a 0x0b and SPL
> > > could not match that to a hardware device. BOOT_DEVICE_SPI is defined as
> > > 0x15 in arch/arm/include/asm/arch-am33xx/spl.h. SPL does not find a
> > > mathch for 0x0b, decides this is an unknown value and stalls. So far so
> > > good.
> > > 
> > > I looked up in the technical reference manual if the value 0x15 is
> > > correct. I had TRM rev. F on my harddrive and found the value in
> > > 26.1.10.2, on page 4295 and it is indeed 0x15 as in u-boot.
> > > I looked on TI website for a new version of the TRM and they currently
> > > have
> > > rev. L. There I found in 26.1.10.2 on page 4960 that SPI boot has 0x0b!
> > > 
> > > My question is now how to best cope with this issue and if anybody has
> > > more
> > > information on what happend.
> > > I don't know if they only made a mistake in the TRM and fixed that or if
> > > they have new silicone revisions that really have another boot device
> > > value for spi boot.
> > > What can we do ?
> > 
> > Sorry for the late reply.  It sounds like at some point post PG2.1 TI
> > changed at least the value used for SPI boot.  I have in the past
> > validated SPI boot on my AM335x GP EVM with PG2.1 silicon.  SPI boot on
> > this hardware is not supported officially due to I believe hardware
> > design issues.  Did you make any further progress here?  Did making the
> > value U-Boot checks by 0x0b make things suddenly work?  Thanks!
> 
> I am not sure what you mean by "PG 2.1". Is that TI silicone revision ? 

Yes.

> According to the Sitara AM335x silicon errata the lasted revision they have 
> out now is revision 2.1 which is the one I have tested on. So they must have 
> changed the SPI boot value BEFORE revision 2.1.
> Yeah, the thing I did was just to change the SPI boot value in the u-boot 
> source and then SPI boot worked fine frome that on.
> I would propose to let u-boot simply accept both values. They do not interfere 
> with some other boot value. That should work for all revisions. What do you 
> think ?

I think we should just re-work things to accept either value.  I would
have sworn that I tested SPI booting on my AM335x GP EVM with the
current silicon version (2.1) but it's also enough of a pain that I
don't think it's worth re-validating things.  There's already a few
fixups in
arch/arm/cpu/armv7/omap-common/boot-common.c::save_omap_boot_params so
adding in one more is fine.

-- 
Tom
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