Re: [PATCH 1/3] Add ARM tune file overhaul based largely on work from Mark Hatle

[Khem Raj <raj.khem@gmail.com>]

On 07/27/2011 07:44 AM, Phil Blundell wrote:
> On Wed, 2011-07-27 at 09:27 -0500, Mark Hatle wrote:
>> On 7/27/11 8:33 AM, Richard Purdie wrote:
>>> On Wed, 2011-07-27 at 13:17 +0100, Phil Blundell wrote:
>>>> On Tue, 2011-07-26 at 13:44 +0100, Richard Purdie wrote:
>>>>> +TARGET_FPU = "${@d.getVar('ARMPKGSFX_FPU', True).strip('-') or 'soft'}"
>>>>
>>>> This seems a bit backwards.  Shouldn't TARGET_FPU be the primary
>>>> variable and then the package suffix be computed from that, rather than
>>>> vice versa?
>>>
>>> It's been "fun" to use the rather limited constructs we have in these
>>> variables to construct the end result. I suspect this way around, it was
>>> the easiest way to get the right variables in the right places.
>>>
>>>>> +ARMPKGSFX_THUMB .= "${@bb.utils.contains("TUNE_FEATURES", [ "armv4", "thumb" ], "t", "", d)}"
>>>>> +ARMPKGSFX_THUMB .= "${@bb.utils.contains("TUNE_FEATURES", [ "armv5", "thumb" ], "t", "", d)}"
>>>>> +ARMPKGSFX_THUMB .= "${@bb.utils.contains("TUNE_FEATURES", [ "armv6", "thumb" ], "t2", "", d)}"
>>>>> +ARMPKGSFX_THUMB .= "${@bb.utils.contains("TUNE_FEATURES", [ "armv7", "thumb" ], "t2", "", d)}"
>>>>
>>>> This is wrong: ARMv6 doesn't imply Thumb-2.
>>>
>>> Ah, yes. I'll fix this.
>>
>> Are you sure?  I thought ARMv6 -was- the first to support Thumb-2.  And armv5/4
>> were thumb(1).  Note, not all ARMv6 processors contain thumb support.
>
> It is true that all ARMv4T and ARMv5T processors are only Thumb-1.  It's
> also true that Thumb-2 was first implemented in ARM1156, which is an
> ARMv6 core.  But ARM1136, ARM1176 and ARM11MPCore are also ARMv6 cores
> and all three of those are Thumb-1 only.  Given that nobody is likely to
> target ARM1156 with OE, it's probably a reasonable approximation to say
> that Thumb-2 correlates with ARMv7 and later.
>
> Also, since there are no v5, v6 or v7 cores which don't support Thumb,

cortex-m series supports only thumb2 intsruction set. I am not sure if 
thumb2 alone is a superset of thumb1 iow thumb1 programs could be 
executed on cortex-m series or not. Never had a cortex-m so I am not sure.

> the "t" suffix serves no useful purpose here and might as well just be
> omitted.  That is, there is no CPU which can run "armv6" packages which
> wouldn't also be able to run "armv6t".
>
>> In the original work I did it was just tune-xscale (no be).  AFAIK there is no
>> little endian version of xscale.
>
> No, that's incorrect.  The PXA25x series and IXP420, at least, are
> bi-endian (and I suspect most of the other XScales are too) and there
> are certainly folks running them in little endian configurations.

nslu2 which uses xscale has both be and le versions of SlugOS

>
> p.
>
>
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