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Re: [Qemu-devel] [PATCH] ARM: Permit any ARMv6K CPU to read the MVFR0 an


From: Peter Maydell
Subject: Re: [Qemu-devel] [PATCH] ARM: Permit any ARMv6K CPU to read the MVFR0 and MVFR1 VFP registers.
Date: Wed, 28 Mar 2012 16:24:46 +0100

On 28 March 2012 15:37, Andrew Towers <address@hidden> wrote:
> From: Andrew Towers <address@hidden>
>
> Replaces the ARM_FEATURE_VFP3 check when reading MVFR0/1 with a check for
> ARM_FEATURE_V6K. Rationale: MVFR0/1 were introduced in the ARM1136 at the
> same time as ARMv6K, and a survey of TRMs indicates support in later models.
>
> According to reference documentation on arm.com, MVFR0 and MVFR1 were
> introduced in ARM1136JF-S r1p1 (ARMv6K, VFPv2). They are also present in
> ARM1156T2F-S and ARM1176JZF-S, which contain VFP11 r5, and in ARM11 MPCore
> r1 which contains VFP11 r4.
>
> Reference (ARM DDI 0211H, 0290G, 0301H, 0360E)
> http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0211h/Ffbefjag.html

Unfortunately I think the ARM1156 is the exception which demonstrates that
this isn't a V6K feature. The 1156 isn't V6K (it doesn't have the TLS registers
or the byte/half/doubleword load/store exclusive instructions), but it does
have the MVFR* registers. So I think we need a new ARM_FEATURE_MVFR flag, and
in cpu_reset_model_id() have V6K imply MVFR.

> Yes, I am slightly abusing the versatilepb hw emulation, but then so is
> everyone else in the world who is still waiting for their Raspberry Pi ;)

...I've been wondering if anybody's going to submit patches for an actual
rPi board model :-)

-- PMM



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