Re: [Qemu-devel] [PATCH v2] ARM: Permit any ARMv6K CPU to read the MVFR0 and MVFR1 VFP registers.

[Andreas Färber]

Am 29.03.2012 14:41, schrieb Andrew Towers:
> This patch replaces the ARM_FEATURE_VFP3 test when reading MVFR registers
> with a test for a new feature flag ARM_FEATURE_MVFR, and sets this feature
> for all ARMv6K cores (ARM1156 is not a v6K core, yet supports MVFR; qemu
> does not support ARM1156 at this time.)
> 
> MVFR0 and MVFR1 were introduced in ARM1136JF-S r1p0 (ARMv6K, VFPv2) and are
> present in ARM1156T2F-S (non-v6K), ARM1176JZF-S, ARM11MPCore and newer cores.
> Reference: ARM DDI 0211H, 0290G, 0301H, 0360E.
> http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0211h/Ffbefjag.html
> 
> Without this change, the linux kernel will not boot with VFP support enabled
> under ARM1176 system emulation, due to the unconditional use of MVFR1 at the
> end of vfp_init() in arch/arm/vfp/vfpmodule.c:
> 
>   VFP support v0.3: implemetor 41 architecture 1 part 20 variant b rev 5
>   Internal error: Oops - undefined instruction: 0 [#1]
> 
> Signed-off-by: Andrew Towers <address@hidden>

Feature inference looks good,

Reviewed-by: Andreas Färber <address@hidden>

> ---
> 
> v2:
>  * introduced ARM_FEATURE_MVFR, implied by ARM_FEATURE_V6K.
> 
> Paul: I'd love to work on an rPi board model, and I'll see what I can put
> together, but much of the hardware is under NDA and I'm not in the loop..

You might find the partial bcm2835 manual helpful:
http://www.raspberrypi.org/archives/615

Open-source drivers (esp. Linux) are also often a helpful source for
emulating NDA'ed hardware.

Regards,
Andreas

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