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 07:49 AM, Mark Hatle wrote:
> On 7/27/11 9:33 AM, Koen Kooi wrote:
>>
>> Op 27 jul. 2011, om 16:27 heeft Mark Hatle het volgende geschreven:
>>
>>> 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 .= "${@bb.utils.contains("TUNE_FEATURES", [ "armv7", "thumb" ], "t2", "", d)}"
>>>>>
>>>>> This is wrong: ARMv6 doesn't imply Thumb-2.
>>>>
>>>> Ah, yes. I'll fix this.
>>>
>>> Are you sure?  I thought ARMv6 -was- the first to support Thumb-2.  And armv5/4
>>> were thumb(1).  Note, not all ARMv6 processors contain thumb support.
>>
>> As I understand it:
>>
>> arm1136 doesn't have t2
>> arm1176 does have t2
>>
>> both are armv6 :)
>
> They also don't have "thumb" support either.  So armv6&  thumb == t2.
>
>>>
>>>>>> +# Whether to compile with code to allow interworking between the two
>>>>>> +# instruction sets. This allows thumb code to be executed on a primarily
>>>>>> +# arm system and vice versa. It is strongly recommended that DISTROs not
>>>>>> +# turn this off - the actual cost is very small.
>>>>>> +TUNEVALID[no-thumb-interwork] = "Disable mixing of thumb and ARM functions"
>>>>>> +TUNE_CCARGS += "${@bb.utils.contains("TUNE_FEATURES", "no-thumb-interwork", "-mno-thumb-interwork", "-mthumb-interwork", d)}"
>>>>>> +OVERRIDES .= "${@bb.utils.contains("TUNE_FEATURES", "no-thumb-interwork", ":thumb-interwork", "", d)}"
>>>>>
>>>>> This is only relevant for v4t, I guess.  Interworking is basically
>>>>> always on for v5 and later and (CeSI aside) it's impossible on v4, so
>>>>> hardly anybody is going to be flipping this switch.  I'm not sure it
>>>>> really merits an OVERRIDE.
>>>>
>>>> I'd be happy to remove this option if there are no objections. It was
>>>> left for compatibility with the existing tune-thumb file but as you say,
>>>> it likely doesn't make much sense.
>>>>
>>>>>> --- a/meta/conf/machine/include/tune-xscale.inc
>>>>>> +++ b/meta/conf/machine/include/tune-xscale.inc
>>>>>> @@ -1,11 +1,17 @@
>>>>>> -require conf/machine/include/arm/arch-arm.inc
>>>>>> +DEFAULTTUNE ?= "xscale"
>>>>>>
>>>>>> -INHERIT += "siteinfo"
>>>>>> +require conf/machine/include/arm/arch-armv5-dsp.inc
>>>>>>
>>>>>> -TUNE_CCARGS = "-march=armv5te -mtune=xscale"
>>>>>> -TARGET_CC_KERNEL_ARCH = "-march=armv5te -mtune=xscale"
>>>>>> -TUNE_PKGARCH = "${@['armv5teb', 'armv5te'][bb.data.getVar('SITEINFO_ENDIANESS', d, 1) == 'le']}"
>>>>>> -PACKAGE_EXTRA_ARCHS = "${@['armeb armv4b armv4tb armv5teb', 'arm armv4 armv4t armv5te'][bb.data.getVar('SITEINFO_ENDIANESS', d, 1) == 'le']}"
>>>>>> +TUNEVALID[xscale] = "Enable PXA255/PXA26x Xscale specific processor optimizations"
>>>>>> +TUNE_CCARGS += "${@bb.utils.contains("TUNE_FEATURES", "xscale", "-mtune=xscale", "", d)}"
>>>>>> +
>>>>>> +AVAILTUNES += "xscale"
>>>>>> +TUNE_FEATURES_tune-xscale = "${TUNE_FEATURES_tune-armv5te} xscale"
>>>>>> +PACKAGE_EXTRA_ARCHS_tune-xscale = "${PACKAGE_EXTRA_ARCHS_tune-armv5te}"
>>>>>> +
>>>>>> +AVAILTUNES += "xscale-be"
>>>>>> +TUNE_FEATURES_tune-xscale = "${TUNE_FEATURES_tune-armv5teb} xscale"
>>>>>> +PACKAGE_EXTRA_ARCHS_tune-xscale = "${PACKAGE_EXTRA_ARCHS_tune-armv5teb}"
>>>>>
>>>>> I guess that should be "_tune-xscale-be".
>>>>
>>>> Yes, I'll fix, well spotted.
>>>
>>> In the original work I did it was just tune-xscale (no be).  AFAIK there is no
>>> little endian version of xscale.  (there was an iwmmxt that was similar to
>>> xscale, but was slightly different.)
>>
>> pxa25x are LE xscales (e.g. Palm Treo)
>> pxa26x are LE xscales with some NAND builtin
>> pxa27x are LE xscales with iwmmxt as an extra
>
> All thought all of those were considered to me iwmmxt cores.  The whole PXA
> series naming is very confusing to say the least.
>

arm cores support both endians equally well. Its the usecases we have on 
OE are little endian.