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List:       openocd-development
Subject:    Re: [OpenOCD-devel] 16-bit CFI flash detection with big endian MIPS
From:       Pete Batard <pete () akeo ! ie>
Date:       2013-06-30 20:05:49
Message-ID: 51D08F9D.6040306 () akeo ! ie
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Hi Oleksij, thanks for the reply.

On 2013.06.30 07:15, Oleksij Rempel wrote:
> right now i'm fighting one of broadcom SOCs. But it seems like yours is
> other kind. Can you please tell which EJTAG version is it?

I actually have no idea. Is there a way to find out that information 
without having the datasheet?
 From what I gather, Broadcom seems to be very tight lipped about 
revealing any kind of useful data about its SoCs, at least publicly.

> Any way. About endians
> you can check CP0 Status and Config registers by using this commands:
> mips32 cp0 12 0
> mips32 cp0 15 0

Not much luck here:

 > mips32 cp0 12 0
couldn't access reg 12
 > mips32 cp0 15 0
couldn't access reg 15

To be fair, it doesn't look like I can get any insightful data from any 
registers when using the current OpenOCD against this SoC. Every single 
register I poke reports zero, including PC (and I can't resume execution 
either).

> Now to your flash.
> I see that you set 16bit bus mode and 16 bit flash mode. But manually
> you tests 0x1fc00020 which according to your flash doc should be 8bit mode.

Aha, that's a good point.

> Till now i never seen that manufacture decided to reduce flash size to
> performance. I mean if you use 16bit mode, you will get half size for
> same price ;)
>
> Try some thing like this:
> flash bank $_FLASHNAME cfi 0x1fc00000 0x00400000 1 1 $_TARGETNAME x16_as_x8

Actually the line above is what I started with, but it's only when I 
used 16bit that I was able to get the expected:
   Flash Manufacturer/Device: 0x227e 0x0001

However, I think you're right: there's something fishy with using x16 
access if the relevant data is provided from the x8 addresses, so the 
flash is most likely in x8 or x16_as_x8 mode.

> may be you'll need different address: 0xbe000000

That's a good suggestion. I'll try to poke different base addresses in 
x8 mode and see what I can get.

Many thanks for the pointers.

Regards,

/Pete

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