Re: Question about the SMP8634/SMP8635 MIPS processor

[Cyril HAENEL <chaenel@free.fr>]

David Daney a écrit :
> Cyril HAENEL wrote:
> [...]
>> The SMP8635 processor comes from Sigma Design and I found on its FTP 
>> site a 2.6.15 kernel with associated patches for the SMP863x 
>> processors serie.
>>
>> My problem is that they doesn't provide the datasheet alone, visibly 
>> they provide it with the SMP8634 developement board 
>> (http://www.sigmadesigns.com/public/Products/SMP8630/SMP8630_series.html). 
>>
>>
>
> In the past the datasheet was only available under NDA...
Maybe I can ask them....
Or maybe I must buy the development kit, but I thing price will be very 
high !

>
>> And to begin to developp on this board, I need at least to know where 
>> is located the JTAG. It will be the starting point to try to access 
>> the NOR flash to backup the original firmware, and play with the board.
>> I don't see any SPI eeprom/flash thus I think even the boot loader is 
>> located the 16MB nor flash, so I thing at startup the processor 
>> directly try to execute code from the NOR, maybe at adress 0x0.
>>
>
> The 8634 has an internal 'security' processor that executes code out 
> of on-chip flash/RAM.  This security processor boots the main CPU only 
> after verifying that the boot loader's cryptographic signatures are 
> valid.    Unless the factory firmware is permissive, there is very 
> little you can do with it.
Ok, thus the 8635 has an internal flash and some security routine at 
startup. Not a good new for me :(
This cryptographic signature are only done on the boot loader ?

>
>> Is someone has some information on this processor ? Or maybe the 
>> datasheet ? With the datasheet I will be have to locate the JTAG pin :)
>
> The JTAG is multiplexed with the second serial port.  Often you have 
> to change a strapping pin so that JTAG is enabled when the board is 
> powered on.  Different boards have a variety of JTAG connectors, you 
> would have to search for it on your board.  Generally it is some form 
> of 14 pin dual-inline header.
Ok, so I have found it. With the scope when I power up the board I can 
see a clock signal and a data signal on a non connected 14 pin header. 
It should be the second serial port you talk about.

>
> If you haven't already found it, probably the first thing you want to 
> do is find primary serial port.  Most configurations print at least a 
> couple of lines indicating DRAM configuration before booting.  If you 
> are lucky you may be able to get to a YAMON prompt from the serial port.
>
> The zboot loader may read a character from the serial port. '0', '1', 
> '2', and '3' will override the default boot image.
I really don't know where the first serial port can be located. The 
other non mounter header are connected to an auxiliary microcontroller. 
I need to search again !

Regards,
Cyril
>
>
> David Daney
>
>
>

-- 

Cyril Haenel
Registered Linux User #332632