Hi Alex, A. Brand wrote, > Hi together, > > normally i work bare metal on Cortex-M devices. But with devices such as the > Cortex-M7 with more than 200MHz, i think of using uclinux for my coming IoT > applications. > > How is the actual status of the Cortex-M7 Support? My first Target will be the > STM32F769 Discovery board.
I can not speak for the uClinux distribution, I can only tell from my point of view. Buildroot does have sample defconfigs and tested support for Cortex-M4 (stm32f429_disco_defconfig / stm32f469_disco_defconfig). They use uClibc-ng and simple C applications incuding Linuxthreads should work fine. As binary format, FLAT is used. > As i read the discussions according FPU support for arm v7m devices, i can not > use the gnu arm gcc toolchain by arm hosted at: https://launchpad.net/ > gcc-arm-embedded > because this toolchain was linked against newlib, am i right? I need a least > one linked against uClib? Not sure, may be this depends on the functions you want to use from the C library. I have read newlib has some kind of FPU support. > So to get a toolchain supporting a arm v7m with fpv5-sp-d16 i need to add a > configuration for the cortex-m7 to buildroot. According to this thread: > http://buildroot-busybox.2317881.n4.nabble.com/ > PATCH-00-16-ARM-Cortex-M-support-td129310.html i have to adapt the dropped > patch for the FPU support of the M4 to the M7 FPU. > > Ok then i have a toolchain, but as i read through the thread why the FPU patch > was dropped, it seems i have another problem. > > The V7M port of linux mainline has no support for the CONFIG_VFP option. It > seems fpu register stack save for task switches is not implemented yet. Is > that > right? Were in the source tree can i look at the > hardware dependent code for the task switch? So i can try to add lazy fpu > register save an test it. > > In search of a maintainer of the stm32 port i found Alexandre Torgues branch > at > kernel.org as the one with the latest commits. But i found no recent commits > on > fpu handling. May be Maxime Coquelin knows more about it, as he seems to be involved in STM32 bootloader afboot-stm32, kernel and openocd for this targets. But why do you think there is some hardware dependent code involved? https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/arch/arm/kernel/signal.c?id=refs/tags/v4.10-rc2 > Thanks for reading this novel. > > Does anybody have any suggestions where i can start my development? > Which toolchain to use? Buildroot, something manually built? > On which branch of the kernel should i clone? > > Thanks in advance. You can try looking at http://www.emcraft.com to see if they support FPU's in their ARM Cortex-M products. https://github.com/EmcraftSystems There is an evaluation to use FDPIC as binary format, it involves toolchain and kernel modifications: https://github.com/mickael-guene/fdpic_manifest The toolchain is built as soft-float. Rob Landley and Rich Felker started porting musl to ARM noMMU devices. There requirement is FDPIC support in gcc and kernel, as Musl does not support FLAT binaries. http://www.openwall.com/lists/musl/2016/12/07/2 Do not read the complete thread, as Rob and I diverged to discuss other topics ;) And _that_ is a novel ;) <selfpromotion> If you want to try an underdog project with fresh Cortex-M7 toolchain support, try http://www.openadk.org/ </selfpromotion> Or if this is all too confusing, keep going using bare-metal ;) http://www.st.com/content/ccc/resource/technical/document/application_note/10/6b/dc/ea/5b/6e/47/46/DM00047230.pdf/files/DM00047230.pdf/jcr:content/translations/en.DM00047230.pdf best regards Waldemar _______________________________________________ uClinux-dev mailing list uClinux-dev@uclinux.org http://mailman.uclinux.org/mailman/listinfo/uclinux-dev This message was resent by uclinux-dev@uclinux.org To unsubscribe see: http://mailman.uclinux.org/mailman/options/uclinux-dev
