Firmware downgrade from 1.3 to 1.2 possible - Page 3 - maemo.org

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marcaurell	2012-12-06 , 16:58
Posts: 33 \| Thanked: 11 times \| Joined on Aug 2012	#21

Originally Posted by eljonker

Can you share the guide to do that?

PLEASE PLEASE post a Guide for downgrade

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rainisto	2012-12-06 , 18:48
Posts: 1,067 \| Thanked: 2,383 times \| Joined on Jan 2012 @ Finland	#22

Originally Posted by marcaurell

PLEASE PLEASE post a Guide for downgrade

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)...

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Last edited by rainisto; 2012-12-06 at 18:52.

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juiceme	2012-12-06 , 22:31
Community Council \| Posts: 4,920 \| Thanked: 12,867 times \| Joined on May 2012 @ Southerrn Finland	#23

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.

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pali	2012-12-06 , 22:36
Posts: 2,154 \| Thanked: 8,464 times \| Joined on May 2010	#24

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

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rainisto	2012-12-06 , 22:46
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Originally Posted by pali

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

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.

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juiceme	2012-12-07 , 08:55
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Originally Posted by rainisto

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)

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

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pali	2012-12-07 , 10:58
Posts: 2,154 \| Thanked: 8,464 times \| Joined on May 2010	#27

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

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Hurrian	2012-12-07 , 11:03
Posts: 1,225 \| Thanked: 1,905 times \| Joined on Feb 2011 @ Quezon City, Philippines	#28

Originally Posted by rainisto

(And if there is ever PR upgrade it would force Nokia to lock CAL even in normal mode)...

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.

Originally Posted by juiceme

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.

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!)

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juiceme	2012-12-07 , 11:14
Community Council \| Posts: 4,920 \| Thanked: 12,867 times \| Joined on May 2012 @ Southerrn Finland	#29

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...)

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pali	2012-12-07 , 11:33
Posts: 2,154 \| Thanked: 8,464 times \| Joined on May 2010	#30

Originally Posted by Hurrian

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!)

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