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[00/16] remove eight obsolete architectures

Message ID 20180314143529.1456168-1-arnd@arndb.de
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Series remove eight obsolete architectures | expand

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Arnd Bergmann March 14, 2018, 2:34 p.m. UTC 
Here is the collection of patches I have applied to my 'asm-generic' tree
on top of the 'metag' removal. This does not include any of the device
drivers, I'll send those separately to a someone different list of people.

The removal came out of a discussion that is now documented at
https://lwn.net/Articles/748074/

Following up from the state described there, I ended up removing the
mn10300, tile, blackfin and cris architectures directly, rather than
waiting, after consulting with the respective maintainers.

However, the unicore32 architecture is no longer part of the removal,
after its maintainer Xuetao Guan said that the port is still actively
being used and that he intends to keep working on it, and that he will
try to provide updated toolchain sources.

In the end, it seems that while the eight architectures are extremely
different, they all suffered the same fate: There was one company in
charge of an SoC line, a CPU microarchitecture and a software ecosystem,
which was more costly than licensing newer off-the-shelf CPU cores from
a third party (typically ARM, MIPS, or RISC-V). It seems that all the
SoC product lines are still around, but have not used the custom CPU
architectures for several years at this point.

      Arnd

Arnd Bergmann (14):
  arch: remove frv port
  arch: remove m32r port
  arch: remove score port
  arch: remove blackfin port
  arch: remove tile port
  procfs: remove CONFIG_HARDWALL dependency
  mm: remove blackfin MPU support
  mm: remove obsolete alloc_remap()
  treewide: simplify Kconfig dependencies for removed archs
  asm-generic: siginfo: remove obsolete #ifdefs
  Documentation: arch-support: remove obsolete architectures
  asm-generic: clean up asm/unistd.h
  recordmcount.pl: drop blackin and tile support
  ktest: remove obsolete architectures

David Howells (1):
  mn10300: Remove the architecture

Jesper Nilsson (1):
  CRIS: Drop support for the CRIS port

Dirstat only (full diffstat is over 100KB):

   6.3% arch/blackfin/mach-bf548/include/mach/
   4.5% arch/blackfin/mach-bf609/include/mach/
  26.3% arch/blackfin/
   4.1% arch/cris/arch-v32/
   5.6% arch/cris/include/arch-v32/arch/hwregs/iop/
   4.1% arch/cris/include/arch-v32/mach-a3/mach/hwregs/
   4.7% arch/cris/include/arch-v32/
   7.8% arch/cris/
   5.6% arch/frv/
   5.5% arch/m32r/
   7.0% arch/mn10300/
   7.6% arch/tile/include/
   6.4% arch/tile/kernel/
   0.0% Documentation/admin-guide/
   0.0% Documentation/blackfin/
   0.0% Documentation/cris/
   0.0% Documentation/devicetree/bindings/cris/
   0.0% Documentation/devicetree/bindings/interrupt-controller/
   2.8% Documentation/features/
   0.5% Documentation/frv/
   0.0% Documentation/ioctl/
   0.0% Documentation/mn10300/
   0.0% Documentation/
   0.0% block/
   0.0% crypto/
   0.0% drivers/ide/
   0.0% drivers/input/joystick/
   0.0% drivers/isdn/hisax/
   0.0% drivers/net/ethernet/davicom/
   0.0% drivers/net/ethernet/smsc/
   0.0% drivers/net/wireless/cisco/
   0.0% drivers/pci/
   0.0% drivers/pwm/
   0.0% drivers/rtc/
   0.0% drivers/spi/
   0.0% drivers/staging/speakup/
   0.0% drivers/usb/musb/
   0.0% drivers/video/console/
   0.0% drivers/watchdog/
   0.0% fs/minix/
   0.0% fs/proc/
   0.0% fs/
   0.0% include/asm-generic/
   0.0% include/linux/
   0.0% include/uapi/asm-generic/
   0.0% init/
   0.0% kernel/
   0.0% lib/
   0.0% mm/
   0.0% samples/blackfin/
   0.0% samples/kprobes/
   0.0% samples/
   0.0% scripts/mod/
   0.0% scripts/
   0.0% tools/arch/frv/include/uapi/asm/
   0.0% tools/arch/m32r/include/uapi/asm/
   0.0% tools/arch/mn10300/include/uapi/asm/
   0.0% tools/arch/score/include/uapi/asm/
   0.0% tools/arch/tile/include/asm/
   0.0% tools/arch/tile/include/uapi/asm/
   0.0% tools/include/asm-generic/
   0.0% tools/scripts/
   0.0% tools/testing/ktest/examples/
   0.0% tools/testing/ktest/

Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-block@vger.kernel.org
Cc: linux-ide@vger.kernel.org
Cc: linux-input@vger.kernel.org
Cc: netdev@vger.kernel.org
Cc: linux-wireless@vger.kernel.org
Cc: linux-pwm@vger.kernel.org
Cc: linux-rtc@vger.kernel.org
Cc: linux-spi@vger.kernel.org
Cc: linux-usb@vger.kernel.org
Cc: dri-devel@lists.freedesktop.org
Cc: linux-fbdev@vger.kernel.org
Cc: linux-watchdog@vger.kernel.org
Cc: linux-fsdevel@vger.kernel.org
Cc: linux-arch@vger.kernel.org
Cc: linux-mm@kvack.org
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Comments

David Howells March 15, 2018, 9:42 a.m. UTC | #1 
Do we have anything left that still implements NOMMU?

David
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Geert Uytterhoeven March 15, 2018, 9:48 a.m. UTC | #2 
Hi David,

On Thu, Mar 15, 2018 at 10:42 AM, David Howells <dhowells@redhat.com> wrote:
> Do we have anything left that still implements NOMMU?

Sure: arm, c6x, m68k, microblaze, and  sh.

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
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Arnd Bergmann March 15, 2018, 9:56 a.m. UTC | #3 
On Thu, Mar 15, 2018 at 10:42 AM, David Howells <dhowells@redhat.com> wrote:
> Do we have anything left that still implements NOMMU?

Yes, plenty. I was wondering the same thing, but it seems that the architectures
we remove are almost completely representative of what we support overall,
except that they are all not licensed to 3rd parties, unlike many of the ones we
keep.

I've made an overview of the remaining architectures for my own reference[1].
The remaining NOMMU architectures are:

- arch/arm has ARMv7-M (Cortex-M microcontroller), which is actually
gaining traction
- arch/sh has an open-source J2 core that was added not that long ago,
it seems to
  be the only SH compatible core that anyone is working on.
- arch/microblaze supports both MMU/NOMMU modes (most use an MMU)
- arch/m68k supports several NOMMU targets, both the coldfire SoCs and the
  classic processors
- c6x has no MMU

       Arnd

[1] https://docs.google.com/spreadsheets/d/1QxMvW5jpVG2jb4RM9CQQl27-wVpNYOa-_3K2RVKifb0
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Hannes Reinecke March 15, 2018, 9:59 a.m. UTC | #4 
On 03/15/2018 10:42 AM, David Howells wrote:
> Do we have anything left that still implements NOMMU?
> 
RISC-V ?
(evil grin :-)

Cheers,

Hannes
Arnd Bergmann March 15, 2018, 10:42 a.m. UTC | #5 
On Thu, Mar 15, 2018 at 10:59 AM, Hannes Reinecke <hare@suse.de> wrote:
> On 03/15/2018 10:42 AM, David Howells wrote:
>> Do we have anything left that still implements NOMMU?
>>
> RISC-V ?
> (evil grin :-)

Is anyone producing a chip that includes enough of the Privileged ISA spec
to have things like system calls, but not the MMU parts?

I thought at least initially the kernel only supports hardware that has a rather
complete feature set.

       Arnd
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Christoph Hellwig March 15, 2018, 2:17 p.m. UTC | #6 
On Thu, Mar 15, 2018 at 11:42:25AM +0100, Arnd Bergmann wrote:
> Is anyone producing a chip that includes enough of the Privileged ISA spec
> to have things like system calls, but not the MMU parts?

Various SiFive SOCs seem to support M and U mode, but no S mode or
iommu.  That should be enough for nommu Linux running in M mode if
someone cares enough to actually port it.
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afzal mohammed March 16, 2018, 4:50 a.m. UTC | #7 
Hi,

On Thu, Mar 15, 2018 at 10:56:48AM +0100, Arnd Bergmann wrote:
> On Thu, Mar 15, 2018 at 10:42 AM, David Howells <dhowells@redhat.com> wrote:

> > Do we have anything left that still implements NOMMU?

Please don't kill !MMU.

> Yes, plenty.

> I've made an overview of the remaining architectures for my own reference[1].
> The remaining NOMMU architectures are:
> 
> - arch/arm has ARMv7-M (Cortex-M microcontroller), which is actually
> gaining traction

ARMv7-R as well, also seems ARM is coming up with more !MMU's - v8-M,
v8-R. In addition, though only of academic interest, ARM MMU capable
platform's can run !MMU Linux.

afzal

> - arch/sh has an open-source J2 core that was added not that long ago,
> it seems to
>   be the only SH compatible core that anyone is working on.
> - arch/microblaze supports both MMU/NOMMU modes (most use an MMU)
> - arch/m68k supports several NOMMU targets, both the coldfire SoCs and the
>   classic processors
> - c6x has no MMU
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Palmer Dabbelt March 20, 2018, 5:11 p.m. UTC | #8 
On Thu, 15 Mar 2018 03:42:25 PDT (-0700), Arnd Bergmann wrote:
> On Thu, Mar 15, 2018 at 10:59 AM, Hannes Reinecke <hare@suse.de> wrote:
>> On 03/15/2018 10:42 AM, David Howells wrote:
>>> Do we have anything left that still implements NOMMU?
>>>
>> RISC-V ?
>> (evil grin :-)
>
> Is anyone producing a chip that includes enough of the Privileged ISA spec
> to have things like system calls, but not the MMU parts?
>
> I thought at least initially the kernel only supports hardware that has a rather
> complete feature set.

We currently do not have a NOMMU port.  As far as I know, everyone who's
currently producing RISC-V hardware with enough memory to run Linux has S mode
with paging support.  The ISA allows for S mode without paging but there's no
hardware for that -- if you're going to put a DRAM controller on there then
paging seems pretty cheap.  You could run a NOMMU port on a system with S-mode
and paging, but With all the superpage stuff I don't think you'll get an
appreciable performance win for any workload running without an MMU so there's
nothing to justify the work (and incompatibility) of a NOMMU port there.

While I think you could implement a NOMMU port on a machine with only M and U
modes (and therefor no address translation at all), I don't know of any MU-only
machines that have enough memory to run Linux (ours have less than 32KiB).  A
SBI-free Linux would be a prerequisite for this, but there's some interest in
that outside of a NOMMU port so it might materialize anyway.

Of course, QEMU could probably be tricked into emulating one of these machines
with little to no effort :)...  That said, I doubt we'll see a NOMMU port
materialize without some real hardware as it's a lot of work for a QEMU-only
target.
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