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Re: [RFC][PATCH 0/2] Make sparcv8 work again on cas enabled hardware
- From: David Miller <davem at davemloft dot net>
- To: rth at twiddle dot net
- Cc: triegel at redhat dot com, andreas at gaisler dot com, libc-alpha at sourceware dot org, adhemerval dot zanella at linaro dot org, carlos at redhat dot com, software at gaisler dot com
- Date: Fri, 04 Nov 2016 11:31:00 -0400 (EDT)
- Subject: Re: [RFC][PATCH 0/2] Make sparcv8 work again on cas enabled hardware
- Authentication-results: sourceware.org; auth=none
- References: <1478187561.7146.742.camel@localhost.localdomain> <20161103.132213.598669006383889263.davem@davemloft.net> <af38a965-24a4-3baf-40e5-7629103a0b1e@twiddle.net>
From: Richard Henderson <rth@twiddle.net>
Date: Fri, 4 Nov 2016 07:55:04 -0600
> On 11/03/2016 11:22 AM, David Miller wrote:
>> From: Torvald Riegel <triegel@redhat.com>
>> Date: Thu, 03 Nov 2016 16:39:21 +0100
>>
>>> Is there any difference between the additional CAS on a v8 and the CAS
>>> on a v9? If there should be none (eg, same instruciton encoding
>>> etc.),
>>> we wouldn't need a runtime check for this, would we?
>>
>> A quick look at binutils shows that the encoding appears to be the
>> same.
>
> Yes and no. The instruction format is the same, but the ASI used is
> different.
>
> The CAS for leon userspace uses ASI_USERDATA (0x0A), not the v9 ASI_P
> (0x80). It's a really annoying difference that I wish the cpu
> designers hadn't made.
I don't think they had much choice in the matter given how the ASIs
are doled out in v9 vs. pre-v9. :-/