Newer MTK chipsets

Mychaela Falconia mychaela.falconia at
Wed Apr 19 18:07:54 UTC 2017

Hi DS,

Thanks for taking a look at this newer MTK stuff.

> note there's no information on wether a signature check is enforced
> by the modem loader like what is done in modern SoC.

I am not too worried about this aspect, as my interest is strictly in
making our own hardware starting from bare chips like we've done with
FCDEV3B, as opposed to hacking various complete devices made by one
unworthy mainstream manuf or another.

My understanding of the commonplace SoC restricted boot mechanisms is
that typically there are OTP fuses on the die in which the device
manuf programs a hash of their public key, and once these fuses have
been programmed, the restricted bootloader will only accept signed
code images verifiable with a public key that matches the fused hash.

But it is my understanding that the signing keys are typically
controlled by the manufacturers of complete devices, rather than the
makers of bare chips, thus if *we* act in the role of the complete
device manuf, buying bare chips on the Chinese grey market like we've
done with the Calypso, then we can make our FreeMTK phone/modem
products only accept firmware images signed by *us*, or leave the
fuses unprogrammed, in which case the chip would presumably accept any
code image.

Instead what I see as the biggest problem would be finding a suitable
chip to use.  It appears that everyone else is only interested in
those disgusting Android slab phones, and the only MTK chipsets people
talk about are the ones with built-in bazillion-core application
processors, the ones that are only suitable for building those darned
Android slab phones and nothing else.  Instead the kind of MTK chip I
am looking for would be one that is just a modem, *without* the
bazillion-core Android part, or alternatively a dumbphone-oriented
chip in which the same single low-end ARM core performs both modem
protocol stack and dumbphone UI functions, i.e., the same thing as TI
Calypso & LoCosto and MT6260 (MTK's 2G-only dumbphone chip), but with
3G/UMTS capability in addition to GSM/2G.  I have not been able to
find any information on the latter kind of MTK chips so far, but they
surely must exist.  Has anyone else found anything in this direction?

> From a quick glance those repositories contain the modem in precompiled
> form, a set of .a files provided by mediatek along with a set of headers.

This part is definitely a bummer.  For as long as there are GSM/2G
networks still operating, our FreeCalypso phones and modems are still
leagues ahead of everyone else in terms of user freedom and
empowerment, as we have the full source as opposed to blobs for the
GSM+GPRS protocol stack and L1.  But if T-Mobile USA shuts down their
GSM/2G services in my neck of the woods (they are the last remaining
GSM/2G network over here) and I lack the economic means to relocate to
some third-world village where I could set up my own GSM cell without
anyone noticing it, then we may have to look into building a 3G-capable
device for which our "free" firmware would only be a thin shim around
a big mass of binary blobs... :-(


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