18.03.2012 19:44, davidMbrooke пишет: > Hi all, > > I'm trying to understand the valid values for our various "architecture" > variables in MasterInclude.mk (ARCH, KARCHS, GNU_ARCH, GNU_TUNE) in the > context of cross-compiled builds. > > I'm OK with GNU_ARCH and GNU_TUNE because I can see those are driving > the setting of -march and -mtune for GCC and they are covered in the GCC > documentation (http://gcc.gnu.org/onlinedocs/gcc/Submodel-Options.html) > > For Bering-uClibc 4.x our make/MasterInclude.mk specifies: > -march=$(GNU_ARCH) -mtune=$(GNU_TUNE) > where: > $(GNU_ARCH) = i486 > $(GNU_TUNE) = pentiumpro > > Then there is KARCHS, where we have multiple variants (i686, i486, > geode). This is effectively just a way to have different Kernels based > on different Kernel .config settings, and hence different kernel Modules > and different Initrd files. I'm OK with this since I understand how we > added support for KARCHS in Bering-uClibc 4.x and how the Kernel .config > patching works. In the Kernel .config we have settings like > CONFIG_M686=y, for i686. > > The bit I don't understand (or at least didn't, until I started > composing this mail, several hours ago) is ARCH, which is set to "i386" > for Bering-uClibc 4.x. > > Based on my investigations today it looks like ARCH is fundamentally a > Kernel configuration setting and the value of ARCH must match the name > of a directory under e.g. linux-3.2.11/arch/ - with a couple of special > cases accommodated in linux-3.2.11/Makefile, for example i386 and x86_64 > both relate to directory linux-3.2.11/arch/x86/. Within the > Kernel .config for ARCH:=i386 we have CONFIG_X86=y and then some > adjustments for i686, geode etc. as part of KARCHS. > > There is also an "architecture" selection for uClibc which we seem to > match to the value of ARCH. For Bering-uClibc 4.x we configure uClibc > with TARGET_ARCH=i386 but we also specify TARGET_SUBARCH=i486 and > CONFIG_486=y. That means that our "i386" toolchain is actually an *i486* > toolchain, which I think we all understand and we accept that we only > build one set of LRP executables for x86 devices. > > > My primary motivation is to understand what all these variables should > be set to for non-x86 platforms such as ARM. For example the Raspberry > Pi has a Broadcom BCM2835 chip containing an ARM1176JZFS CPU. That is > part of the ARM11 processor family built on the ARMv6 architecture, so > for GCC we'd want to set -march=armv6 (or possibly -march=armv6zk) and > then maybe -mtune=arm1176jzf-s. > > In terms of Kernel configuration we'd want to specify ARCH:=ARM (and > hence CONFIG_ARM=y) and then CONFIG_ARCH_BCMRING=y (which looks to be > the equivalent of e.g. CONFIG_M686=y or CONFIG_MGEODE_LX=y so would be > configured via KARCHS). > > I'm therefore thinking, for the Raspberry Pi: > ARCH = arm > KARCHS = bcmring > GNU_ARCH = armv6 > GNU_TUNE = arm1176jzf-s > > In the uClibc .config I'd want to set TARGET_arm=y, TARGET_ARCH="arm" > and CONFIG_ARM1176JZF_S=y (which then compiles uClibc with -march=armv6 > and -mtune=arm1176jzf-s based on the settings in Rules.mak). That means > we'd have an "armv6" toolchain rather than a generic "arm" toolchain. Hi. ARCH defines for what ARCH is cross-compiled kernel (ARCH=$(ARCH) make). It needs to be specified because in other case make oldconfig/make menuconfig will try to change settings for current host arch. KARCHS - list of kernel variants (and related modules). IMHO it should be unique for each embedded platform/family of very similar platforms. GNU_ARCH - CPU type for which userland is built, GNU_TUNE - for which CPU variant userland will be optimized (because userland will run on different CPU sub-archs). > > I'm also thinking about what the "ARCH" arguments to buildtool.pl and > buildpacket.pl should look like. Maybe we just use the GCC "target > triplet" syntax, so e.g. > i486-pc-linux-uclibc for the Bering-uClibc 4.x platform > armv6-unknown-linux-uclibc for the Raspberry pi > > In other words, "buildtool.pl --target=i486-pc-linux-uclibc build ..." > rather than "buildtool.pl --arch=i386 build ..." > > Thoughts? > > David AFAIK there is no difference between '-pc-linux-uclibc' and '-unknown-linux-uclibc' suffixes, and IMHO it'll be safe to use i486-unknown-linux-uclibc arch.
------------------------------------------------------------------------------ This SF email is sponsosred by: Try Windows Azure free for 90 days Click Here http://p.sf.net/sfu/sfd2d-msazure _______________________________________________ leaf-devel mailing list leaf-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/leaf-devel
