[Sugar-devel] Strange problem, a big size number in xo4's screen.

[James Cameron]

G'day Buddhi,

Thanks for your question.  Your question is not about Sugar, but I'll
reply here because there are some people who may be interested.

This problem is seen with low frequency and has known causes.

Please tell me the SKU, the affected serial numbers, how many laptops
affected, and how many laptops unaffected?  I use this for measuring
the problem.

My recommendations are;

(a) now, repair the affected laptops using serial adapter [1] and SPI
FLASH recovery for XO-4 using CForth [2],

(b) in future, identify laptops likely to be affected (see below) and
before reflashing remove charger and main battery for 30 seconds,

(c) in future, when firmware reflash does hang, do not turn off,
instead connect a serial adapter and repair,

(d) now, if the number of laptops is too high, reinforce normal
precautions for handling and storage.


In more detail;

Electrostatic discharge, high altitude radiation, extreme
temperatures, humidity or physical shock can cause temporary
malfunction of the CPU, memory, and SPI FLASH chip.  Malfunction
may be invisible until firmware reflash is started.

Firmware reflash may hang.  At this time some blocks are correctly
written with new firmware, some blocks are erased, and some
blocks have old firmware.

e.g. "NNNNNEOOO" instead of "NNNNNNNNN", where "N" is new, "E" is
erased, and "O" is old firmware.

Combined with your power off, the damage to SPI FLASH data means the
XO-4 cannot start.


In much deeper detail;

The symbol "10" is during startup after CForth has run and before Open
Firmware has turned on memory management unit and caches.

https://github.com/quozl/openfirmware/blob/olpc/cpu/arm/mmp3/resetvec.fth#L143

The symbol "16" is during startup after Open Firmware has unpacked and
processor cache is synchronised to memory.

https://github.com/quozl/openfirmware/blob/olpc/cpu/arm/mmp3/resetvec.fth#L232

Both "10" and "16" can be result of interrupted reflashing.

The full list of symbols is;

"00" CForth before loading Open Firmware,
"01" CForth after loading but before executing,
"10" Open Firmware before turning on memory management unit and caches,
"11" Open Firmware after turning on memory management unit and caches,
"12" Open Firmware before inflating dropin,
"13" Open Firmware after inflating dropin,
"14" Open Firmware with uncompressed dropin,
"15" Open Firmware after dropin is written to cache, and
"16" Open Firmware after cache is synchronised to memory.

CForth is in the first block of SPI FLASH, and can be used via serial
adapter.

References:

1.  http://wiki.laptop.org/go/Serial_adapters
2.  http://wiki.laptop.org/go/SPI_FLASH_Recovery_for_XO-4_Using_CForth

On Wed, Dec 13, 2017 at 03:49:13PM +0545, Buddhi Tuladhar wrote:
> Dear all,
> 
> I am facing this strange problem in XO4. Every time i start xo4 a big size
> number appears in screen eg 10,16 . Below i have links of the picture of xo4
> screen. this problem appears after flashing the xo with the custom image i
> build, it is not frequent but sometimes while flashing xo4's firmware, it gets
> stuck in the middle and everything stops. After that only thing i can do is to
> press power button and off it, then after that if i try to on the xo, big size
> number appears. I cannot even go to "ok prompt" to re flash the xo. It is
> creating a big problem for me. If anyone can guide me to solve this problem i
> would be very thankful.
> 
> [1]http://download.olenepal.org/xo10.jpg
> [2]http://download.olenepal.org/xo16.jpg
> 
> Regards,
> Buddhi Raj Tuladhar,
> OLE Nepal Tech Team
> 
> References:
> 
> [1] http://download.olenepal.org/xo10.jpg
> [2] http://download.olenepal.org/xo16.jpg

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-- 
James Cameron
http://quozl.netrek.org/