[PATCH-for-5.2] target/mips: Deprecate nanoMIPS ISA

[Philippe Mathieu-Daudé]

The nanoMIPS ISA has been announced in 2018 for various projects:

GCC:   https://gcc.gnu.org/legacy-ml/gcc/2018-05/msg00012.html
Linux: https://lwn.net/Articles/753605/
QEMU:  https://www.mail-archive.com/qemu-devel@nongnu.org/msg530721.html

Unfortunately the links referenced doesn't work anymore (www.mips.com).

>From this Wayback machine link [1] we can get to a working place to
download a toolchain (a more recent release than the one referenced
in the announcement mails):
http://codescape.mips.com/components/toolchain/nanomips/2018.04-02/downloads.html

The toolchain page mention LLVM but simply links http://llvm.org/
where there is no reference on nanoMIPS.

The only reference in the GCC mailing list, is the nanoMIPS
announcement: https://gcc.gnu.org/pipermail/gcc/2018-May.txt

The developer who authored the announcements have been emailed [2]
to ask for more information but all their emails are now bouncing:

- Your message to Stefan.Markovic@mips.com couldn't be delivered.

- Your message to smarkovic@wavecomp.com couldn't be delivered.

- Couldn't deliver the message to the following recipients:
    Robert.Suchanek@mips.com, matthew.fortune@mips.com,
    marcin.nowakowski@mips.com

Our deprecation policy do not allow feature removal before 2 release,
therefore declare the nanoMIPS ISA code deprecated as of QEMU 5.2.
This gives time to developers to update the QEMU community, or
interested parties to step in to maintain this code.

[1] 
https://web.archive.org/web/20180904044530/https://www.mips.com/develop/tools/compilers/
[2] https://www.mail-archive.com/qemu-devel@nongnu.org/msg756392.html

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
---
 docs/system/deprecated.rst | 23 +++++++++++++++++++++++
 MAINTAINERS                |  6 +++++-
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/docs/system/deprecated.rst b/docs/system/deprecated.rst
index 32a0e620dbb..a26af200c73 100644
--- a/docs/system/deprecated.rst
+++ b/docs/system/deprecated.rst
@@ -310,6 +310,13 @@ to build binaries for it.
 ``Icelake-Client`` CPU Models are deprecated. Use ``Icelake-Server`` CPU
 Models instead.
 
+MIPS ``I7200`` CPU Model (since 5.2)
+''''''''''''''''''''''''''''''''''''
+
+The ``I7200`` guest CPU relies on the nanoMIPS ISA, which is deprecated
+(the ISA has never been upstreamed to a compiler toolchain). Therefore
+this CPU is also deprecated.
+
 System emulator devices
 -----------------------
 
@@ -413,6 +420,13 @@ The ``ppc64abi32`` architecture has a number of issues 
which regularly
 trip up our CI testing and is suspected to be quite broken. For that
 reason the maintainers strongly suspect no one actually uses it.
 
+MIPS ``I7200`` CPU (since 5.2)
+''''''''''''''''''''''''''''''
+
+The ``I7200`` guest CPU relies on the nanoMIPS ISA, which is deprecated
+(the ISA has never been upstreamed to a compiler toolchain). Therefore
+this CPU is also deprecated.
+
 Related binaries
 ----------------
 
@@ -477,6 +491,15 @@ versions, aliases will point to newer CPU model versions
 depending on the machine type, so management software must
 resolve CPU model aliases before starting a virtual machine.
 
+Guest Emulator ISAs
+-------------------
+
+nanoMIPS ISA
+''''''''''''
+
+The ``nanoMIPS`` ISA has never been upstreamed to any compiler toolchain.
+As it is hard to generate binaries for it, declare it deprecated.
+
 
 Recently removed features
 =========================
diff --git a/MAINTAINERS b/MAINTAINERS
index 2c22bbca5ac..4f701012eea 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -227,7 +227,7 @@ R: Aleksandar Rikalo <aleksandar.rikalo@syrmia.com>
 S: Odd Fixes
 F: target/mips/
 F: default-configs/*mips*
-F: disas/*mips*
+F: disas/mips.c
 F: docs/system/cpu-models-mips.rst.inc
 F: hw/intc/mips_gic.c
 F: hw/mips/
@@ -240,6 +240,10 @@ F: include/hw/timer/mips_gictimer.h
 F: tests/tcg/mips/
 K: ^Subject:.*(?i)mips
 
+MIPS TCG CPUs (nanoMIPS ISA)
+S: Orphan
+F: disas/nanomips.*
+
 Moxie TCG CPUs
 M: Anthony Green <green@moxielogic.com>
 S: Maintained
-- 
2.26.2