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From:   Geert Uytterhoeven <geert@linux-m68k.org>
Date:   Wed, 18 Jan 2023 08:46:58 +0100
Message-ID: <CAMuHMdXo3iR2C=CAaXO5tBRCncnQAAMR6BMPLOm_nBpFAeVhrA@mail.gmail.com>
Subject: Re: remove arch/sh
To:     Rob Landley <rob@landley.net>
Cc:     Christoph Hellwig <hch@lst.de>,
        John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>,
        Yoshinori Sato <ysato@users.sourceforge.jp>,
        Rich Felker <dalias@libc.org>, Arnd Bergmann <arnd@arndb.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
        Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>,
        Geert Uytterhoeven <geert+renesas@glider.be>,
        linux-kernel@vger.kernel.org, linux-watchdog@vger.kernel.org,
        devicetree@vger.kernel.org, linux-arch@vger.kernel.org,
        dmaengine@vger.kernel.org, dri-devel@lists.freedesktop.org,
        linux-renesas-soc@vger.kernel.org, linux-i2c@vger.kernel.org,
        linux-input@vger.kernel.org, linux-media@vger.kernel.org,
        linux-mmc@vger.kernel.org, linux-mtd@lists.infradead.org,
        netdev@vger.kernel.org, linux-gpio@vger.kernel.org,
        linux-rtc@vger.kernel.org, linux-spi@vger.kernel.org,
        linux-serial@vger.kernel.org, linux-usb@vger.kernel.org,
        linux-fbdev@vger.kernel.org, alsa-devel@alsa-project.org,
        linux-sh@vger.kernel.org
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Hi Rob,

On Wed, Jan 18, 2023 at 5:50 AM Rob Landley <rob@landley.net> wrote:
> On 1/17/23 14:26, Geert Uytterhoeven wrote:
> > On Tue, Jan 17, 2023 at 8:01 PM Rob Landley <rob@landley.net> wrote:
> >> I'm lazy and mostly test each new sh4 build under qemu -M r2d because it's
> >> really convenient: neither of my physical boards boot from SD card so replacing
> >> the kernel requires reflashing soldered in flash. (They'll net mount userspace
> >> but I haven't gotten either bootloader to net-boot a kernel.)
> >
> > On my landisk (with boots from CompactFLASH), I boot the original 2.6.22
> > kernel, and use kexec to boot-test each and every renesas-drivers
> > release.  Note that this requires both the original 2.6.22 kernel
> > and matching kexec-tools.
>
> I make it a point to run _current_ kernels in all my mkroot systems, including
> sh4. What I shipped was 6.1 is:
>
> # cat /proc/version
> Linux version 6.1.0 (landley@driftwood) (sh4-linux-musl-cc (GCC) 9.4.0, GNU ld
> (GNU Binutils) 2.33.1) #1 Tue Jan 10 16:32:07 CST 2023

I think you misunderstood: renesas-drivers releases[1] are current
kernels.

   Linux version 6.2.0-rc3-landisk-01864-g0c6453b3e5f6 (geert@rox)
(sh4-linux-gnu-gcc (Ubuntu 11.3.0-1ubuntu1~22.04) 11.3.0, GNU ld (GNU
Binutils for Ubuntu) 2.38) #125 Tue Jan 10 14:29:01 CET 2023

I use 2.6.22 and kexec as a boot loader for newer kernels, to avoid
juggling CF cards.  I cannot install a newer base kernel on the CF,
as kexec is broken upstream.

> > Apparently both upstreamed kernel and
> > kexec-tools support for SH are different, and incompatible with each
> > other, so you cannot kexec from a contemporary kernel.
>
> Sure you can. Using toybox's insmod and modprobe, anyway. (That's the target I
> tested those on... :)
>
> Haven't messed with signing or compression or anything yet, my insmod is just
> doing syscall(SYS_finit_module) and then falling back to SYS_init_module if that
> fails and either fd was 0 or errno was ENOSYS. (Don't ask me why
> SYS_finit_module doesn't work on stdin...)
>
> https://github.com/landley/toybox/blob/master/toys/other/insmod.c#L31
>
> https://landley.net/toybox/downloads/binaries/0.8.9/toybox-sh4

Again, I think you're talking about something different.
Does kexec work for you?

> > I tried working my way up from 2.6.22, but gave up around 2.6.29.
> > Probably I should do this with r2d and qemu instead ;-)
>
> I have current running there. I've had current running there for years. Config
> attached...
>
> > Both r2d and landisk are SH7751.
>
> Cool. Shouldn't be hard to get landisk running current then.

Current kernels work fine on landisk with an old Debian userspace
on CF.  The 8139cp driver is a bit flaky: last time I tried nfsroot,
that didn't work well.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/geert/renesas-drivers.git

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds