Re: [ptxdist] ptxdist with iMX6

[Michael Olbrich <m.olbrich@pengutronix.de>]

Hi,

On Thu, Mar 02, 2017 at 03:50:19PM +0100, Guillermo Rodriguez Garcia wrote:
> 2017-03-01 22:03 GMT+01:00 Alexander Dahl <post@lespocky.de>:
> > Hei hei,
> >
> > On Wed, Mar 01, 2017 at 06:36:38PM +0100, Guillermo Rodriguez Garcia wrote:
> >> Is someone using ptxdist with iMX6 based targets? I know phytec used
> >> ptxdist in the past but now they seem to be using Yocto instead.
> >
> > We have a phytec i.MX6 dev board at work. They shipped a ptxdist based
> > BSP in the first place before they switched to ptxdist. I had
> > Distrokit working with it, I guess when Linux 3.18 was bleeding edge,
> > but did not manage to send it upstream.
> >
> > So in general i.MX6 works, I guess it's basically getting your
> > bootloader and kernel config working?
> 
> Yes, indeed. Selecting the right kernel to start from is already a
> non-trivial task, given the plethora of options (we have at least:
> official Freescale/NXP kernels, community kernels, vendor kernels from
> board/SOM manufacturers, and the upstream kernel).
> 
> >
> >> Re. toolchain: Any recommended version of OSELAS.Toolchain? Best
> >> settings to finetune for Cortex A9 + VFPv3 + NEON ?
> >
> > I would recommend the latest release v2016.06.1 and go with
> > arm-v7a-linux-gnueabihf_gcc-5.4.0_glibc-2.23_binutils-2.26_kernel-4.6-sanitized.ptxconfig
> 
> That is a great start. Some things that draw my attention, though:
> 
> - VFPv3-D16 selected whereas iMX6 can do VFPv3-D32 (or just "VFPv3")
> - NEON not enabled (supported by iMX6)

For the glibc this makes no real difference. It has neon optimizes memcpy
etc. that is selected at runtime. Maybe some math functions are slower, but
I've not heard of any issues there. For the BSP just set TARGET_EXTRA_CFLAGS
/ TARGET_EXTRA_CXXFLAGS to add the appropriate -mcpu/-mfpu.

> - Thumb mode used by default (not sure why -- wouldn't it be more
> appropriate to use arm mode by default unless there is an explicit
> intent to optimize size over speed ?)

For ARMv7 thumb means thumb2 and that is just as fast as arm mode but uses
less space. All bit distros use this as well.

Michael

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