[U-Boot] [PATCH] i.MX31: fir imx31_phycore to work after Linux reboot

[Guennadi Liakhovetski]

On Fri, 6 Feb 2009, Wolfgang Denk wrote:

> Dear Guennadi Liakhovetski,
> 
> In message <Pine.LNX.4.64.0902061002160.4970 at axis700.grange> you wrote:
> > Upon power on i.MX31 enables most peripheral clocks, Linux disables the ones
> 
> Why does U-Boot do that?

i.MX31 does that - the CPU, not U-Boot. I.e., this is the default power-on 
mode.

> This is against U-Boot design guidelines which state that U-Boot shall
> only activate such peripherals that it uses itself.
> 
> > didn't use I2C, the clock would stay disabled. And U-Boot on imx31_phycore
> > uses an I2C EEPROM for environment data. So, after a reboot U-Boot would be
> 
> That's another area of bad design. Should we not change U-Boot such
> that it places the environment in flash?

Hm, no idea who and why decided to do that. I can only guess that this 
comes from the original BSPs somewhere, maybe they wanted to ship various 
EEPROM versions while keeping the same NOR, although both are probably 
hard-soldered on the CPU board (cannot recognise the eeprom, can be under 
the barcode label). And maybe they have some user-space tools of their own 
to access that EEPROM... no, not defending, just trying to guess what we 
might break if we switch.

> BTW: What does "fir imx31_phycore to work after Linux reboot" mean? I
> cannot parse that.

Sorry, s/fir/fix/.

Thanks
Guennadi
---
Guennadi Liakhovetski, Ph.D.

DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: +49-8142-66989-0 Fax: +49-8142-66989-80  Email: office at denx.de