Hi Waldemar, thanks for ur reply.
Waldemar Brodkorb <w...@openadk.org> schrieb am Mo., 2. Jan. 2017 um 18:43 Uhr: > 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. > I actually build this configuration already, with stock buildroot configuration. Due to the similarities between the stm32 lines i should try to boot this on my hardware. > 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. > My question was not concerning the libs support. I think of building the kernel with hard float support, cause i plan to make heavy use of floating point in a device driver. > > > 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 To my shame i have not looked at the code. So i will resurrect the patches from the linked thread, port them to my needs and give it a try. > > > 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 I have my problems with using a toolchain from 2010 with a cpu from 2017. I dont see that emcraft is using an other toolchain than stated here: https://www.emcraft.com/som/stm32f7-212/installing-activating-cde furthermore this doc was updated in sep. 2016. > > > 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 ;) > This is totally weird stuff. I will definitely have a eye on FDPIC, but for me its in a too early stage and i have to little experience in this area. > > <selfpromotion> > If you want to try an underdog project with fresh Cortex-M7 toolchain > support, try http://www.openadk.org/ > </selfpromotion> > I will give it a try. Maybe i contribute a configuration for the F769. > > 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 No this is boring, its my every day work, nothing for a hobby :). regrads, Alex
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