Content from 2016-09

Intro

It took some playing around, but I have finally managed to figure out how to build from source all the tools necessary to put Zephyr on Arduino 101. You may say that the effort is pointless because you could just use whatever is provided by the SDK. For me, however, the deal is more about what I can learn from the experience that about the result itself. There is enough open source code around to make things work reasonably well, but putting it all together is a bit of a challenge, so what follows is a short HOWTO.

Arduino 101 setup
Arduino 101 setup

Toolchain

Arduino 101 has a Quark core and an ARC EM core. The appropriate targets seem to be i586-none-elfiamcu and arc-none-elf for the former and the later respectively. Since there is no pre-packaged toolchain for either of these in Debian, you'll need to build your own. You can use the vanilla binutils (version 2.27 worked for me) and the vanilla newlib (version 2.4.0.20160527 did not require any patches). GCC is somewhat more problematic. Since apparently not all the necessary ARC patches have been accepted into the mainline yet, you'll need to download it from the Synopsys GitHub repo. GDB requires tweaking for both cores.

binutils:

]==> mkdir binutils && cd binutils
]==> wget https://ftp.gnu.org/gnu/binutils/binutils-2.27.tar.bz2
]==> tar jxf binutils-2.27.tar.bz2
]==> mkdir i586-none-elfiamcu && cd i586-none-elfiamcu
]==> ../binutils-2.27/configure --prefix=/home/ljanyst/Apps/cross-compilers/i586-none-elfiamcu --target=i586-none-elfiamcu
]==> make -j12 && make install
]==> cd .. && mkdir arc-none-elf && arc-none-elf
]==> ../binutils-2.27/configure --prefix=/home/ljanyst/Apps/cross-compilers/arc-none-elf --target=arc-none-elf
]==> make -j12 && make install
]==> cd ../..

gcc:

]==> mkdir gcc && cd gcc
]==> wget ftp://ftp.uvsq.fr/pub/gcc/releases/gcc-6.2.0/gcc-6.2.0.tar.bz2
]==> tar jxf gcc-6.2.0.tar.bz2
]==> git clone git@github.com:foss-for-synopsys-dwc-arc-processors/gcc.git
]==> cd gcc && git checkout arc-4.8-dev && cd ..
]==> mkdir i586-none-elfiamcu && cd i586-none-elfiamcu
]==> ../gcc-6.2.0/configure --prefix=/home/ljanyst/Apps/cross-compilers/i586-none-elfiamcu --target=i586-none-elfiamcu --enable-languages=c --with-newlib
]==> make -j12 all-gcc && make install-gcc
]==> cd .. && mkdir arc-none-elf && arc-none-elf
]==> ../gcc/configure --prefix=/home/ljanyst/Apps/cross-compilers/arc-none-elf --target=arc-none-elf  --enable-languages=c --with-newlib --with-cpu=arc700
]==> make -j12 all-gcc && make install-gcc
]==> cd ../..

newlib:

]==> mkdir newlib && cd newlib
]==> wget ftp://sourceware.org/pub/newlib/newlib-2.4.0.20160527.tar.gz
]==> tar zxf newlib-2.4.0.20160527.tar.gz
]==> mkdir i586-none-elfiamcu && cd i586-none-elfiamcu
]==> ../newlib-2.4.0.20160527/configure --prefix=/home/ljanyst/Apps/cross-compilers/i586-none-elfiamcu --target=i586-none-elfiamcu
]==> make -j12 && make install
]==> cd .. && mkdir arc-none-elf && arc-none-elf
]==> ../newlib-2.4.0.20160527/configure --prefix=/home/ljanyst/Apps/cross-compilers/arc-none-elf --target=arc-none-elf
]==> make -j12 && make install
]==> cd ../..

libgcc:

]==> cd gcc/i586-none-elfiamcu
]==> make -j12 all-target-libgcc && make install-target-libgcc
]==> cd ../arc-none-elf
]==> make -j12 all-target-libgcc && make install-target-libgcc
]==> cd ../..

GDB does not work for either platform out of the box. For Quark it compiles the i386 version but does not recognize the iamcu architecture even though, according to Wikipedia, it's essentially the same as i586 and libbfd knows about it. After some poking around the code, it seems that initilizing the i386 platform with iamcu bfd architecture definition does the trick:

 1 diff -Naur gdb-7.11.1.orig/gdb/i386-tdep.c gdb-7.11.1/gdb/i386-tdep.c
 2 --- gdb-7.11.1.orig/gdb/i386-tdep.c     2016-06-01 02:36:15.000000000 +0200
 3 +++ gdb-7.11.1/gdb/i386-tdep.c  2016-09-24 15:39:11.000000000 +0200
 4 @@ -8890,6 +8890,7 @@
 5  _initialize_i386_tdep (void)
 6  {
 7    register_gdbarch_init (bfd_arch_i386, i386_gdbarch_init);
 8 +  register_gdbarch_init (bfd_arch_iamcu, i386_gdbarch_init);
 9  
10    /* Add the variable that controls the disassembly flavor.  */
11    add_setshow_enum_cmd ("disassembly-flavor", no_class, valid_flavors,

For ARC the Synopsys open source repo provides a solution.

]==> mkdir gdb
]==> wget ftp://sourceware.org/pub/gdb/releases/gdb-7.10.1.tar.xz
]==> tar xf gdb-7.11.1.tar.xz
]==> cd gdb-7.11.1 && patch -Np1 -i ../iamcu-tdep.patch && cd ..
]==> git clone git@github.com:foss-for-synopsys-dwc-arc-processors/binutils-gdb.git
]=> cd binutils-gdb && git checkout arc-2016.09-gdb && cd ..
]==> mkdir i586-none-elfiamcu && cd i586-none-elfiamcu
]==> ../gdb-7.11.1/configure --prefix=/home/ljanyst/Apps/cross-compilers/i586-none-elfiamcu --target=i586-none-elfiamcu
]==> make -j12 && make install
]==> cd .. && mkdir arc-none-elf && arc-none-elf
]==> ../binutils-gdb/configure --prefix=/home/ljanyst/Apps/cross-compilers/arc-none-elf --target=arc-none-elf 
]==> make -j12 all-gdb && make install-gdb
]==> ../..

OpenOCD

There was no OpenOCD release for quite some time, and it does not seem to have any support for Quark SE. The situation is not much better if you look at the head of the master branch of their repo. Fortunately, both Intel and Synopsys provide some support for their parts of the platform and making it work with mainline openocd does not seem to be hard.

]==> git clone git@github.com:ljanyst/openocd.git && cd openocd
]==> git checkout lj
]==> ./bootstrap
]==> ./configure --prefix=/home/ljanyst/Apps/openocd
]==> make -j12 && make install

Zephyr uses the following configuration for the Arduino (referred to as openocd.conf below):

 1 source [find interface/ftdi/flyswatter2.cfg]
 2 source [find board/quark_se.cfg]
 3 
 4 quark_se.quark configure -event gdb-attach {
 5         reset halt
 6         gdb_breakpoint_override hard
 7 }
 8 
 9 quark_se.quark configure -event gdb-detach {
10         resume
11         shutdown
12 }

You can use the following commands to run the GDB server, flash for Quark and flash for ARC respectively (this is what Zephyr does):

]==> openocd -s /home/ljanyst/Apps/openocd/share/openocd/scripts/ -f openocd.cfg  -c 'init' -c 'targets' -c 'reset halt'
]==> openocd -s /home/ljanyst/Apps/openocd/share/openocd/scripts/ -f openocd.cfg  -c 'init' -c 'targets' -c 'targets quark_se.arc-em' -c 'reset halt' -c 'load_image zephyr.bin 0x40010000' -c 'reset halt' -c 'verify_image zephyr.bin 0x40010000' -c 'reset run' -c 'shutdown'
]==> openocd -s /home/ljanyst/Apps/openocd/share/openocd/scripts/ -f openocd.cfg  -c 'init' -c 'targets' -c 'targets quark_se.arc-em' -c 'reset halt' -c 'load_image zephyr.bin 0x40034000' -c 'reset halt' -c 'verify_image zephyr.bin 0x40034000' -c 'reset run' -c 'shutdown'

Hello world!

You need to compile and flash Zephyr's Hello World sample. The two commands below do the trick for the compilation part:

make BOARD=arduino_101_factory CROSS_COMPILE=i586-none-elfiamcu- CFLAGS="-march=lakemont -mtune=lakemont -msoft-float -miamcu -O0"
make BOARD=arduino_101_sss_factory CROSS_COMPILE=arc-none-elf-

After flashing, you should see the following on your UART console:

]==> screen /dev/ttyUSB0 115200,cs8
ipm_console0: 'Hello World! arc'
Hello World! x86

Debugging

If you follow the instructions from the Zephyr wiki, debugging for the Intel part works fine. I still have some trouble making breakpoints work for ARC and will try to write an update if I have time to figure it out.

]==> i586-none-elfiamcu-gdb outdir/zephyr.elf
...
(gdb) target remote :3333
Remote debugging using :3333
0x0000fff0 in ?? ()
(gdb) b main
Breakpoint 1 at 0x400100ed: file /home/ljanyst/Projects/zephyr/zephyr-project/samples/hello_world/nanokernel/src/main.c, line 37.
(gdb) c
Continuing.
target running
hit hardware breakpoint (hwreg=0) at 0x400100ed

Breakpoint 1, main () at /home/ljanyst/Projects/zephyr/zephyr-project/samples/hello_world/nanokernel/src/main.c:37
37              PRINT("Hello World! %s\n", CONFIG_ARCH);
(gdb) s
step done from EIP 0x400100ed to 0x400100f2
step done from EIP 0x400100f2 to 0x400100f7
step done from EIP 0x400100f7 to 0x40013129
target running
hit hardware breakpoint (hwreg=1) at 0x4001312f
printk (fmt=0x40013e04 "Hello World! %s\n") at /home/ljanyst/Projects/zephyr/zephyr-project/misc/printk.c:164
164             va_start(ap, fmt);
(gdb) s
step done from EIP 0x4001312f to 0x40013132
step done from EIP 0x40013132 to 0x40013135
165             _vprintk(fmt, ap);
(gdb)

Intro

I have finally received my Kickstarter-backed UP boards. So far they seem great! There are three minor drawbacks, though:

  1. They don't have the exact same shape as Raspberry PI's, so they don't fit the raspberry cases. It's nothing that could not be rectified with small pliers, though.
  2. The audio chip on Cherry Trail (Intel Atom x5 z8350) SoCs is not yet supported by Linux out of the box, so some fiddling with the kernel is necessary.
  3. Debian's UEFI boot configuration does not seem to work from the get-go either.

Boot

You can install Debian Testing using a USB stick. Don't try Jessie, though - the kernel will not detect the MMC card. Things should work fine, except that grub will install itself in /EFI/debian/grubx64.efi on the EFI partition. You will need to move it to /EFI/boot/bootx64.efi manually. It's possible to do it from the UEFI shell using familiar commands.

Media

Kodi installs and works out of the box from Debian Multimedia. Unfortunately, to get the sound working, you will need to recompile the kernel :)

Get the sources and the necessary patches and create the config:

git clone https://github.com/torvalds/linux.git
cd linux
git remote add cht https://github.com/plbossart/sound.git
git fetch cht
git checkout byt-cht-hdmi-v4.7
make oldconfig

You will need to edit .config:

  • to set CONFIG_SYSTEM_TRUSTED_KEYS variable to an empty string
  • to enable CONFIG_HDMI

Then the only thing that's left is building and installing the package:

fakeroot make-kpkg --initrd --append-to-version=-up --revision=1 -j 8 kernel_image kernel_headers
cd ..
sudo dpkg -i linux-image-4.7.0-up+_1_amd64.deb

I wanted to see how efficient it is, so I run the compilation on the board itself. It took roughly 2.5 hours and got very hot. The board can handle perfectly fine the FullHD video files over Samba that Raspberry PI 2 couldn't. The audio quality is much better too. It seems that surround 5.1 actually works. :)

Note 09.11.2017: These drivers have been included into mainline since kernel 4.11. However, you will still need to edit your Alsa settings to choose the default output device. This has worked for me:

]==> cat /etc/asound.conf
defaults.pcm.!card Audio
defaults.ctl.!card Audio
defaults.pcm.!device 2
defaults.ctl.!device 2