Re: [PATCH v1 0/3] Meson A1 32-bit support

[Dmitry Rokosov]

Hello Kevin,

On Thu, Mar 09, 2023 at 01:52:41PM -0800, Kevin Hilman wrote:
> Dmitry Rokosov <ddrokosov@xxxxxxxxxxxxxx> writes:
> 
> > On Mon, Feb 27, 2023 at 07:19:38PM +0100, Arnd Bergmann wrote:
> >> On Mon, Feb 27, 2023, at 17:50, Dmitry Rokosov wrote:
> >> > On Mon, Feb 27, 2023 at 05:38:49PM +0100, Neil Armstrong wrote:
> >> >> On 27/02/2023 17:15, Arnd Bergmann wrote:
> >> >> > On Mon, Feb 27, 2023, at 16:51, Dmitry Rokosov wrote:
> >> >> > 
> >> >> > Most of these don't apply in userspace, so the incentive to
> >> >> > run smaller 32-bit userland on systems with less than 1GB of
> >> >> > RAM usually outweighs the benefits of 64-bit userspace.
> >> >> 
> >> >> Thanks for the details!
> >> >
> >> > Looks like Thomas has already prepared a basic patch series for buildroot,
> >> > but maintainers declined it.
> >> >
> >> > https://lore.kernel.org/all/20220730194331.GA2515056@scaer/
> >> 
> >> I see. I know very little about buildroot, but it sounds like
> >> there are other ways of doing the same thing here. In general,
> >> this is pretty much an Arm specific problem. While you clearly
> >> want compat mode for small userland on any architecture but don't
> >> want 32-bit kernels, arm is the only one that has a different
> >> kernel "ARCH=" value and needs a separate gcc toolchain.
> >> 
> >> If the problem is only the toolchain, an easy way out may
> >> be to use clang instead of gcc as your compiler, as a single
> >> clang binary can target both 32-bit userland and 64-bit kernel
> >> on all supported architectures.
> >
> > Agreed with you. We will try different local approaches to support
> > compat build configurations. For now, prebuilt toolchain (buildroot make
> > sdk goal) is best way from my point of view. Anyway, we will try to
> > solve this problem in the our sandbox and stay on the 64-bit kernel.
> > Thank you for all the helpful details you shared, appreciate it!
> 
> Just to clarify one thing...
> 
> More specifically, this is a buildroot *build system* problem.  If you
> build the kernel separately from the rootfs, it works fine. 
> 
> I use 32-bit buildroot (and debian) rootfs images all the time on
> Amlogic SoCs with 64-bit kernels and it works fine.  

You are totally right. It's one of the possible ways. But in the our
internal project we build kernel + roofs + uboot together in the one
buildroot project ('repo' based). So we will try to stay in the such
paradigm, but will use multi-arch toolchain, maybe.
Anyway, thanks a lot for sharing your experience.

-- 
Thank you,
Dmitry