[OE-core] qemuarm: should it really have TUNE_ARCH armv5te?

Thu Sep 13 12:14:31 UTC 2012

On Thu, Sep 13, 2012 at 11:42:06AM +0100, Richard Purdie wrote:
> On Thu, 2012-09-13 at 08:20 +0200, Martin Jansa wrote:
> > On Wed, Sep 12, 2012 at 03:33:03PM +0100, Richard Purdie wrote:
> > > On Tue, 2012-09-11 at 15:01 +0200, Martin Jansa wrote:
> > > > Hi,
> > > > 
> > > > when building spitz and qemuarm (both produces packages in armv5te feed)
> > > > resulting packages are tuned with -mtune=xscale (when built for spitz) 
> > > > or -mtune=arm926ej-s (when built for qemuarm).
> > > > 
> > > > From
> > > > https://bugzilla.yoctoproject.org/show_bug.cgi?id=1916#c5
> > > > Firstly, if you go changing the tune parameters in a given machine,
> > > > you are expected to use a different PACKAGE_ARCH. If you do that, you
> > > > will get a different package feed for the different binaries,
> > > > different WORKDIR and so on. This was always the way the package
> > > > architectures was intended to work and nothing has changed there. Yes,
> > > > you as the user changing various variables can create inconsistent
> > > > package feeds. There are 101 ways you can do that, the simple answer
> > > > is just don't. We're therefore unlikely to add MACHINE to DEPLOY_DIR
> > > > or remove PACKAGE_ARCH, please just use it as its intended.
> > > > 
> > > > Does qemuarm use oe-core as it's intended?
> > > > 
> > > > Shouldn't spitz produce something like armv5te-xscale and qemuarm armv5te-arm926ejs?
> > > > It would cause all recipes to build again (cannot share armv5te feed anymore),
> > > > but at least it would build it and user will really get it on target, right now
> > > > opkg upgrade can download some packages with xscale some with arm926ej-s.
> > > > 
> > > > $ ~/bitbake/bin/bitbake-diffsigs
> > > >   stamps.1347348910/spitz/armv5te-oe-linux-gnueabi/linux-libc-headers-3.4.3-r0.do_configure.sigdata.04b364a15889fcff7502614f1c116abc
> > > >   stamps.1347348910/qemuarm/armv5te-oe-linux-gnueabi/linux-libc-headers-3.4.3-r0.do_configure.sigdata.656f0583be969b427f040f2e143bcb14
> > > >   basehash changed from 7fe9c0a3455dac20ba6a90ed337b097e to d8dd2ff8613d0aafe60bef1a1e9469a1
> > > >   Variable TUNE_CCARGS value changed from
> > > >   ${@bb.utils.contains("TUNE_FEATURES", "armv5", "-march=armv5${ARMPKGSFX_THUMB}${ARMPKGSFX_DSP}", "", d)}
> > > >   ${@bb.utils.contains("TUNE_FEATURES", "armv4", "-march=armv4${ARMPKGSFX_THUMB}", "", d)}
> > > >   ${@bb.utils.contains("TUNE_FEATURES", "thumb", "${ARM_THUMB_M_OPT}", "", d)}
> > > >   ${@bb.utils.contains("TUNE_FEATURES", "no-thumb-interwork", "-mno-thumb-interwork", "-mthumb-interwork", d)}
> > > >   ${@bb.utils.contains("TUNE_FEATURES", "vfp", bb.utils.contains("TUNE_FEATURES", "callconvention-hard", "-mfloat-abi=hard", "-mfloat-abi=softfp", d), "" ,d)}
> > > >   ${@bb.utils.contains("TUNE_FEATURES", "xscale", "-mtune=xscale", "", d)}
> > > >   to
> > > >   ${@bb.utils.contains("TUNE_FEATURES", "armv5", "-march=armv5${ARMPKGSFX_THUMB}${ARMPKGSFX_DSP}", "", d)}
> > > >   ${@bb.utils.contains("TUNE_FEATURES", "armv4", "-march=armv4${ARMPKGSFX_THUMB}", "", d)}
> > > >   ${@bb.utils.contains("TUNE_FEATURES", "thumb", "${ARM_THUMB_M_OPT}", "", d)}
> > > >   ${@bb.utils.contains("TUNE_FEATURES", "no-thumb-interwork", "-mno-thumb-interwork", "-mthumb-interwork", d)}
> > > >   ${@bb.utils.contains("TUNE_FEATURES", "vfp", bb.utils.contains("TUNE_FEATURES", "callconvention-hard", "-mfloat-abi=hard", "-mfloat-abi=softfp", d), "" ,d)}
> > > >   ${@bb.utils.contains("TUNE_FEATURES", "arm926ejs", "-mtune=arm926ej-s", "", d)}
> > > > 
> > > 
> > > This is a tricky one. As others have mentioned, this is a tune
> > > parameter, not an arch one and as such the binaries are compatible with
> > > each other although they potentially are compiled differently with
> > > different optimisations.
> > > 
> > > As such, mixing the feeds is permitted and will not cause any real world
> > > usage problem. As you point out, sstate is much more sensitive to this
> > > kind of change and is correctly deciding the output is different though.
> > > 
> > > I think my preferred approach would be to have the tune files do
> > > something like:
> > > 
> > > -mtune=${ARMV5TEDEFAULTTUNE}
> > > 
> > > and then the user can set ARMV5DEFAULTTUNE to whatever the believe is a
> > > appropriate. This would result in the package feed at least having a
> > > consistent state of one tune and sstate would be happy. It then becomes
> > > a distro policy decision which is what it should be. ARMV5TEDEFAULTTUNE
> > > would default to the current values meaning the distro would then just
> > > do:
> > > 
> > > ARMV5TEDEFAULTTUNE_poky = "xscale"
> > >
> > > and hence make their decision. Of course the distro could also decide to
> > > split the package architectures up which is equally fine.
> > > 
> > > Does something like that sound like it would work?
> > 
> > My solution seems to be a bit more flexible then this.
> 
> Which cases does it enable which the above doesn't?

To have separate binary feeds for some packages while keeping most of
other packages in armv5te feed without any -mtune or with some
ARMV5TEDEFAULTTUNE.

But -mtune=${ARMV5TEDEFAULTTUNE} in tune-arm926ejs.inc with 
xscale value set through ARMV5TEDEFAULTTUNE_disto doesn't look very
intuitive.

And how many .*DEFAUTTUNE variables distro should set?

Anyway I'll be off for next 10 days or so..

> I'm a little worried about adding more indirection to the DEFAULTTUNE
> variable itself since the whole tune situation is already convoluted and
> indirected enough without adding another level of it :/. That variable
> is the one exposed to the user straight away, not hidden more behind the
> scenes.
> 
> Taking a step back and looking at the APIs I'm really not very happy
> with the usability of them already and I don't think this helps.
> 
> Someone commented about the ppc situation and I was told that there, the
> binaries are incompatible with each other. It is more unusual to have
> situations where there are micro-optimisations through -mtune yet the
> binaries remain compatible.
> 
> Cheers,
> 
> Richard
> 
> 

-- 
Martin 'JaMa' Jansa     jabber: Martin.Jansa at gmail.com
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