Re: Firmware downgrade from 1.3 to 1.2 possible
 

PLEASE PLEASE post a Guide for downgrade

Re: Firmware downgrade from 1.3 to 1.2 possible
 

hopefully nobody will ever release a guide for that, since if you mess up with CAL too much, you can end up with permant brick of your device (even nokia care is not able reflash perm bricked devices). (And if there is ever PR upgrade it would force Nokia to lock CAL even in normal mode)...

Re: Firmware downgrade from 1.3 to 1.2 possible
 

That's actually the reason inception is more dangerous than open mode.

I was thinking about this one day, what lead me to this was some time back somebody had a weird problem, IMEI of the device was corrupted.

The fact that cal is locked when running in open mode helps to protect from random faults that could wreck havoc by writing something to a critical area by mistake. In normal mode, under inception/opensh there is no such protection.

Re: Firmware downgrade from 1.3 to 1.2 possible
 

@rainisto: is there any way how to repair perm bricked devices? and who can that if nokia care not?

Re: Firmware downgrade from 1.3 to 1.2 possible
 

Well in short there is no way.

However if you have done backup from your CAL then you could in theory restore CAL from your backup. BUT before you get your hopes up, only Nokia employees with R&D certificate can backup&restore CAL areas, and all the people that could generate R&D certificates for N9 have already left the company.

And factory line jtag flasher, but its quite unlikely that you get access inside the production factory (and those factory lines are already ramped down anyways).

So in short if you happen to mess up your CAL, you can throw the device in garbage for spare parts and buy a new phone.

Re: Firmware downgrade from 1.3 to 1.2 possible
 

This is propably the only viable way of doing it. BTW, I thought Nokia Service shops would be able to flash the device via JTAG interface...? I mean if there is some repairs done to the RFU the phone needs to be recalibrated, right?

For JTAG flashing you actually do not need fancy equipment, just a cheapy ~200 eur USB/JTAG adapter and some soldering skills is required :D

Re: Firmware downgrade from 1.3 to 1.2 possible
 

Ok, so I must be very very carefull to not damage CAL...

Re: Firmware downgrade from 1.3 to 1.2 possible
 

This would break lock code functionality. Or, they could store the lock code in a file, which is arguably a lot more insecure than storing it in an obscure database no one's bothered to write a library to interface with.

IIRC the IMEI is stored on the BB5 chip, which runs completely separate from the SoC. All the SoC side of the system does is talk to the BB5 over the OMAP's SSI interface.

Something else may have been broken, but it sure isn't corruption of the IMEI.

And if the N9 is just like the N900, you could probably flash_erase /dev/mtd1 and CAL would be able to partially rebuild itself (kids, don't try this at home!)

Re: Firmware downgrade from 1.3 to 1.2 possible
 

OK, if that is so, then where is the MFG calibration data for RFU stored?
I kinda thought it would be in CAL (that it is an abbreviation for CALibration, but maybe I was mistaken...)

Re: Firmware downgrade from 1.3 to 1.2 possible
 

Did you already tried to erase CAL in N900?? Or why are you sure, that N900 CAL can rebuilt it itself?