[i386/686] Enable MGEODE_LX instead of M686 (regression in 4.16)

- x86-32: Disable 3D-Now in generic config

debian/changelog

@@ -156,6 +156,8 @@ linux (4.18.9-1) UNRELEASED; urgency=medium
   [ Ben Hutchings ]
   * drivers/net/ethernet: Ignore ABI changes (fixes FTBFS on arm64, armhf)
   * [arm64] ACPI: Change ACPI_NFIT from built-in to module
+  * [i386/686] Enable MGEODE_LX instead of M686 (regression in 4.16)
+    - x86-32: Disable 3D-Now in generic config
 
   [ Yves-Alexis Perez ]
   * [x86] enable PINCTRL_AMD for touchpad support on Lenovo IdeaPad.

debian/config/i386/config.686

@@ -18,7 +18,9 @@ CONFIG_GEOS=y
 ##
 ## choice: Processor family
 # CONFIG_M486 is not set
-CONFIG_M686=y
+#. We want to support Geode LX and similar AMD family 5 CPUs as well as
+#. family 6+ CPUs
+CONFIG_MGEODE_LX=y
 ## end choice
 
 ##

debian/patches/bugfix/x86/x86-32-disable-3dnow-in-generic-config.patch

@@ -0,0 +1,29 @@
+From: Ben Hutchings <ben@decadent.org.uk>
+Date: Tue, 25 Sep 2018 19:44:13 +0100
+Subject: x86-32: Disable 3D-Now in generic config
+
+We want the 686 flavour to run on Geode LX and similar AMD family 5
+CPUs as well as family 6 and higher CPUs.  This used to work with
+CONFIG_M686=y.  However commit 25d76ac88821 "x86/Kconfig: Explicitly
+enumerate i686-class CPUs in Kconfig" in Linux 4.16 has made the
+kernel require family 6 or higher.
+
+It looks like a sensible choice would be to enable CONFIG_MGEODE_LX
+and CONFIG_X86_GENERIC (for more generic optimisations), but this
+currently enables CONFIG_X86_USE_3D_NOW which will cause the kernel to
+crash on CPUs without the AMD-specific 3D-Now instructions.
+
+Make CONFIG_X86_USE_3DNOW depend on CONFIG_X86_GENERIC being disabled.
+
+---
+--- a/arch/x86/Kconfig.cpu
++++ b/arch/x86/Kconfig.cpu
+@@ -337,7 +337,7 @@ config X86_USE_PPRO_CHECKSUM
+ 
+ config X86_USE_3DNOW
+ 	def_bool y
+-	depends on (MCYRIXIII || MK7 || MGEODE_LX) && !UML
++	depends on (MCYRIXIII || MK7 || MGEODE_LX) && !X86_GENERIC && !UML
+ 
+ #
+ # P6_NOPs are a relatively minor optimization that require a family >=

debian/patches/series

@@ -76,6 +76,7 @@ bugfix/powerpc/powerpc-lib-sstep-fix-building-for-powerpcspe.patch
 bugfix/powerpc/powerpc-lib-makefile-don-t-pull-in-quad.o-for-32-bit.patch
 bugfix/arm/arm-mm-export-__sync_icache_dcache-for-xen-privcmd.patch
 bugfix/arm64/arm64-acpi-Add-fixup-for-HPE-m400-quirks.patch
+bugfix/x86/x86-32-disable-3dnow-in-generic-config.patch
 
 # Arch features
 features/mips/MIPS-increase-MAX-PHYSMEM-BITS-on-Loongson-3-only.patch