Question about the SMP8634/SMP8635 MIPS processor

Question about the SMP8634/SMP8635 MIPS processor

[Cyril HAENEL]

Hi,

I am new to the list, I recently bought a set-top-box (Netbox 8160) 
which uses a SMP8635 MIPS processor.
The original fimware is a disaster and for fun I want to try to build my 
own linux based firmware for this set-to-box.

I am absolutely not afraid, because I do a lot of embedded linux at 
office (on ARM9 arch and Blackfin arch).

The board of this set-top-box is pretty simple, there is the SMP8635 
processor, 256MB of DDRAM, 16 MB of NOR flash, mini pci with atheros 
wifi card, ethernet MII phy, and 2 DVB-T tuners (maybe USB2 or PCI, for 
now I don't now).

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).

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.

Is someone has some information on this processor ? Or maybe the 
datasheet ? With the datasheet I will be have to locate the JTAG pin :)

Thank you for reading my message, and sorry because my english is not 
perfect.

I wish you a good day

Regards,
Cyril HAENEL

-- 

Cyril Haenel
Registered Linux User #332632

Re: Question about the SMP8634/SMP8635 MIPS processor

[David Daney]

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...

> 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.

> 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.

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.


David Daney

Re: Question about the SMP8634/SMP8635 MIPS processor

[Cyril HAENEL]

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