[Skiboot] external/gard: Alternate mtd or FDT entries?

Cyril Bur cyril.bur at au1.ibm.com
Thu Aug 20 11:26:35 AEST 2015

On Tue, 18 Aug 2015 09:49:10 +1000
Stewart Smith <stewart at linux.vnet.ibm.com> wrote:

> Patrick Williams <patrick at stwcx.xyz> writes:
> > Anyone have ideas?
> >
> > Cyril, copying you specifically because you seem to have touched 'gard'
> > subdirectory most.
> Cyril is out with a not-able-to-move-his-left-arm after some skiing
> adventure, so I'll attempt to have a crack at it...

Yes sorry about that, typing one handed now, oh the joy.

> > On Thu, Aug 13, 2015 at 02:09:26PM -0500, Patrick Williams wrote:
> >> I see the 'gard' tool by default will search the FDT entry
> >> "/proc/device-tree/chosen/ibm,system-flash" for the location of the MTD
> >> block device for writing.  I believe that will point us to the 'current'
> >> side.
> >> 

The gard tool has no concept of sides as it expects to find the GUARD record in
TOC at 0. The flash in /proc/device-tree/chosen/ibm,system-flash should be the
entire chip, so it should always find it.

> >> If we were booted from the golden side of PNOR, is there any way for us
> >> to write / clear the non-golden side?  The '-f' option seems to be
> >> exclusively for files and not MTD.
> I think specifying -f should do it, but we'd need a device to poke at
> for the non-golden side, which I *think* we just expose it all as one
> mtd device now?

-f should work for reading but I don't think clearing/writing will work too

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