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Re: [PATCH] Enable AT_PLATFORM for Loongson 2F CPU

To: Robert Millan <rmh@gnu.org>
Subject: Re: [PATCH] Enable AT_PLATFORM for Loongson 2F CPU
From: wu zhangjin <wuzhangjin@gmail.com>
Date: Tue, 9 Nov 2010 17:48:34 +0800
Cc: David Daney <ddaney@caviumnetworks.com>, Aurelien Jarno <aurelien@aurel32.net>, Ralf Baechle <ralf@linux-mips.org>, linux-mips@linux-mips.org
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Hi, Robert

On Tue, Nov 9, 2010 at 7:02 AM, Robert Millan <rmh@gnu.org> wrote:
> 2010/11/8 David Daney <ddaney@caviumnetworks.com>:
>> Look at the description of the register in this document:
>>
>> http://dev.lemote.com/files/resource/documents/Loongson/ls2e/godson2e.user.manual.pdf
>>
>> On page 49, it says that bits 0-3 contain the minor version number and bits
>> 4-7 are the major version number (according to a workmate that reads
>> Chinese).
>>
>> I don't know for certain, but it seems plausible that the 2E and 2F will
>> differ in bits 4-7, and bits 0-3 can be ignored.
>
> Thanks for investigating, but ignoring bits 0-3 doesn't
> really change anything.  Our problem was that bits 0-7
> are the same on 2E and 2F (0x02).  If we ignore bits 0-3,
> then our problem is that bits 4-7 are the same on 2E
> and 2F (0x2).

Just rechecked this with a friend from Lemote, in reality, the
revision id of Loongson-2F is 0x3, so, my old code should be a
reference for you:

arch/mips/loongson/common/platform.c

PRID_REV_LOONGSON2F and PRID_REV_LOONGSON2E has already been defined
in arch/mips/include/asm/cpu.h

So, the manual is buggy, perhaps the editors of the manuals did copy
and paste for I have found the title of the 2F manual is the same as
the 2E manual ;-)

Best Regards,
Wu Zhangjin

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