Re: [dpdk-dev] [PATCH v3 01/17] mk: Introduce ARMv7 architecture

[Jan Viktorin <viktorin@rehivetech.com>]

On Wed, 28 Oct 2015 11:09:21 +0100
David Marchand <david.marchand@6wind.com> wrote:

> Hello Jan,
> 
> On Tue, Oct 27, 2015 at 8:13 PM, Jan Viktorin <viktorin@rehivetech.com>
> wrote:
> 
> >
> > diff --git a/config/defconfig_arm-armv7-a-linuxapp-gcc
> > b/config/defconfig_arm-armv7-a-linuxapp-gcc
> > new file mode 100644
> > index 0000000..5a778cf
> > --- /dev/null
> > +++ b/config/defconfig_arm-armv7-a-linuxapp-gcc
> > +
> > +# avoids using i686/x86_64 SIMD instructions, nothing for ARM
> > +CONFIG_RTE_BITMAP_OPTIMIZATIONS=0
> >  
> 
> (<unrelated>yet another build flag which has to disappear, and bitmap
> header should be moved from librte_sched to eal with arch-specific
> implementations when applicable</unrelated>)
> 
> Well, I am a bit confused by this comment.
> For me, gcc provides ctzll builtins.
> https://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html
> 
> And with your patchset applied, it builds fine with
> RTE_BITMAP_OPTIMIZATIONS enabled using gcc 4.7.3 for arm on ubuntu 14.04.
> Is there a dependency on gcc version ?

It seems, there is no need for this. I will remove it. DPDK compiles
well.

> 
> 
> +# PCI is usually not used on ARM
> > +CONFIG_RTE_EAL_IGB_UIO=n
> >  
> 
> Not sure "usually not used" is a good reason to disable something.
> Is there a real issue on arm with igb_uio code (compilation, pci accesses) ?
> 

Well, it requires to set some options in Linux Kernel (at least PCI
support) which are usually disabled by the in-kernel *arm*_defconfigs.
Moreover, it seems I cannot enable it for some ARM architectures (I've
tried Altera SoC FPGA). That's because you hardly find an ARMv7 system
with a PCI bus. I suppose that if somebody _really_ needs this, she would
enable it by hand.

At the moment, it breaks my common builds... The driver is mostly
useless on ARMv7 and just takes space in the filesystem.

> 
> Thanks.
> 

Regards
Jan



-- 
  Jan Viktorin                E-mail: Viktorin@RehiveTech.com
  System Architect            Web:    www.RehiveTech.com
  RehiveTech
  Brno, Czech Republic