linux-kernel - RE: [RFC] buildtar: add case for riscv architecture

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Date:   Sat, 14 Sep 2019 13:05:59 +0000
From:   Anup Patel <Anup.Patel@....com>
To:     Palmer Dabbelt <palmer@...ive.com>,
        "mail@...abindo.in" <mail@...abindo.in>
CC:     Troy Benjegerdes <troy.benjegerdes@...ive.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        "aou@...s.berkeley.edu" <aou@...s.berkeley.edu>,
        "linux-riscv@...ts.infradead.org" <linux-riscv@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-kbuild@...r.kernel.org" <linux-kbuild@...r.kernel.org>
Subject: RE: [RFC] buildtar: add case for riscv architecture



> -----Original Message-----
> From: linux-kernel-owner@...r.kernel.org <linux-kernel-
> owner@...r.kernel.org> On Behalf Of Palmer Dabbelt
> Sent: Saturday, September 14, 2019 6:30 PM
> To: mail@...abindo.in
> Cc: Troy Benjegerdes <troy.benjegerdes@...ive.com>; Paul Walmsley
> <paul.walmsley@...ive.com>; aou@...s.berkeley.edu; linux-
> riscv@...ts.infradead.org; linux-kernel@...r.kernel.org; linux-
> kbuild@...r.kernel.org
> Subject: Re: [RFC] buildtar: add case for riscv architecture
> 
> On Wed, 11 Sep 2019 05:54:07 PDT (-0700), mail@...abindo.in wrote:
> >
> >
> >> None of the available RiscV platforms that I’m aware of use compressed
> images, unless there are some new bootloaders I haven’t seen yet.
> >>
> >
> > I noticed that default build image is Image.gz, which is why I thought its a
> good idea to copy it into the tarball. Does such a copy not make sense at this
> point ?
> 
> Image.gz can't be booted directly: it's just Image that's been compressed
> with the standard gzip command.  A bootloader would have to decompress
> that image before loading it into memory, which requires extra bootloader
> support.
> Contrast that with the zImage style images (which are vmlinuz on x86), which
> are self-extracting and therefor require no bootloader support.  The
> examples for u-boot all use the "booti" command, which expects
> uncompressed images.
> Poking around I couldn't figure out a way to have u-boot decompress the
> images, but that applies to arm64 as well so I'm not sure if I'm missing
> something.
> 
> If I was doing this, I'd copy over arch/riscv/boot/Image and call it
> "/boot/image-${KERNELRELEASE}", as calling it vmlinuz is a bit confusing to
> me because I'd expect vmlinuz to be a self-extracting compressed
> executable and not a raw gzip file.

On the contrary, it is indeed possible to boot Image.gz directly using
U-Boot booti command so this patch would be useful.

Atish had got it working on U-Boot but he has deferred booti Image.gz
support due to few more dependent changes. May be he can share
more info.

Regards,
Anup