Re: [Qemu-devel] [ARM] Cortex-R4F and VFP3-D16

[Fabien Chouteau <chouteau@adacore.com>]

On 03/01/2013 12:32 PM, Peter Maydell wrote:
> On 1 March 2013 11:21, Fabien Chouteau <chouteau@adacore.com> wrote:
>> TMS570LS31x/21x Technical Reference Manual:
>>
>> "The TMS570 family is based on the ARM® CortexTM-R4F core. ARM has
>> designed this core to be used in big-endian and little-endian systems.
>> For the TI TMS570 family, the endianness has been configured to BE32."
> 
> That is confusing, because ARM's R4F Technical Reference Manual
> says "The processor does not support word-invariant big-endianness
> (BE)-32"...
> 
> (http://translatedcode.wordpress.com/2012/04/02/this-end-up/
> has a quick summary of what the various flavours of ARM
> endianness actually mean.)
> 

Confusing indeed. It seems that the documentation is not reliable. Below
the text I just quoted, there's an example showing that TMS570 is
actually BE8. And this is confirmed by our experience using the real
board.

> I think you're going to have to run some tests on the actual
> hardware to find out what it really does. Specifically, what
> are the values of SCTLR.IE, SCTLR.EE and CPSR.E when you think
> you're in big-endian mode? (We need to sort out what parts of
> the behaviour you're seeing are the CPU itself and what parts
> are the SoC/board doing endianness flipping externally to the
> CPU.)
> 

SCTLR.IE and SCTLR.EE are both set to 1 at reset and the values cannot
be changed.

BTW, our run-time works both on QEMU and a real-board, that's also why
I'm confident that there are no endianness issue.

Regards,

-- 
Fabien Chouteau