[U-Boot] U-Boot 2012.10 - pxa270 CPU Unknown / no turbo

[Andreas Puls]

Dear Marek Vasut,

> Dear Andreas Puls,
> 
> > Dear Marek Vasut,
> > 
> > > Dear Andreas Puls,
> > > 
> > > > Hi together,
> > > > 
> > > > i've got another problem with latest stable U-Boot-2012.10 and a
> > > > Toradex Colibri PXA270 V2.4
> > > > 
> > > > Uboot dosen't regonized the CPU Revision
> > > > u-boot summary screen:
> > > > 
> > > > U-Boot 2012.10 (Nov 12 2012 - 14:22:12)
> > > > CPU: Marvell PXA27x rev. Unknown
> > > 
> > > See arch/arm/cpu/pxa/cpuinfo.c , patch is welcome ... they probably
> > > rolled out
> > > some new CPU version.
> > 
> > Yes, its a PXA270 M. There is a spec. update pdf from Marvel.
> >
> http://www.marvell.com/application-processors/pxa-family/assets/pxa_27x_spe
> > c_update.pdf - Table 2-3.
> > 
> > They changed the Stepping from A0...C5 to "PXA270M -- A1"
> > A colleague would support me to change this becouse i have no cloue
> about
> > writing C Files. So we would like ask you first if the right CPU Name
> > should be shown in the summary screen which would be a rewrite of your
> > function or only the right stepping with the old CPU Name would be
> enough
> > ? (Damn it - hope you understand my Denglish)
> 
> Can the CPUs be distinguished in some deterministic way? If so, rewrite
> it, no 
> problem.


Both CPU types have the same basic CPU ID, only the 4 stepping bits (the
4 LSBs of the CPU ID) are different. So basically the existing functions
could be extended just to handle the new stepping code.

However, the naming scheme of the new CPU type according to the data
sheet is quite different than the older steppings.

Older PXA270 versions have the following CPU ID, wher the last hex digit
(the 4 LSBs) is the stepping code, e.g.:

CPU ID: 0x69054111, stepping code 1 --> PXA270 -- A1

The Marvell Spec Update Manual shows the new Stepping and CPU ID as follows:

CPU ID: 0x69054118, stepping code 8 --> PXA270M -- A1

So for stepping code 8 the revision name A1 is the same as for stepping
code 1, but the CPU base name has changed from PXA270 to PXA270M for the
new type.

So just extending the existing stepping decoding function would lead to
confusion since the existing code would print

   PXA270 rev. A1

for bothe the oldest and the newest CPU type, where something like

   PXA270M rev. A1

would be correct for stepping code 8. I'm not sure which would be the
best way to handle this situation and change the code accordingly.

> Best regards,
> Marek Vasut

Kind regards
   Andreas