[MIPS] Add basic SMARTMIPS ASE support

This patch adds trivial support for SMARTMIPS extension. This extension
is currently implemented by 4KS[CD] CPUs.

Basically it saves/restores ACX register, which is part of the SMARTMIPS
ASE, when needed. This patch does *not* add any support for Smartmips MMU
features.

Futhermore this patch does not add explicit support for 4KS[CD] CPUs since
they are respectively mips32 and mips32r2 compliant.  So with the current
processor configuration, a platform that has such CPUs needs to select
both configs:

	CPU_HAS_SMARTMIPS
	SYS_HAS_CPU_MIPS32_R[12]

This is due to the processor configuration which is mixing up all the
architecture variants and the processor types.

The drawback of this, is that we currently pass '-march=mips32' option to
gcc when building a kernel instead of '-march=4ksc' for 4KSC case. This
can lead to a kernel image a little bit bigger than required.

Signed-off-by: Franck Bui-Huu <fbuihuu@gmail.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

1 files changed, 18 insertions, 0 deletions

diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index c6f74f1c6398..58e97886d771 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -274,6 +274,7 @@ config MIPS_ATLAS
         select SYS_SUPPORTS_BIG_ENDIAN
         select SYS_SUPPORTS_LITTLE_ENDIAN
         select SYS_SUPPORTS_MULTITHREADING if EXPERIMENTAL
+        select SYS_SUPPORTS_SMARTMIPS
         select GENERIC_HARDIRQS_NO__DO_IRQ
         help
           This enables support for the MIPS Technologies Atlas evaluation
@@ -305,6 +306,7 @@ config MIPS_MALTA
         select SYS_SUPPORTS_BIG_ENDIAN
         select SYS_SUPPORTS_LITTLE_ENDIAN
         select SYS_SUPPORTS_MULTITHREADING
+        select SYS_SUPPORTS_SMARTMIPS
         help
           This enables support for the MIPS Technologies Malta evaluation
           board.
@@ -322,6 +324,7 @@ config MIPS_SEAD
         select SYS_SUPPORTS_64BIT_KERNEL if EXPERIMENTAL
         select SYS_SUPPORTS_BIG_ENDIAN
         select SYS_SUPPORTS_LITTLE_ENDIAN
+        select SYS_SUPPORTS_SMARTMIPS
         help
           This enables support for the MIPS Technologies SEAD evaluation
           board.
@@ -1641,6 +1644,18 @@ config 64BIT_PHYS_ADDR
 config CPU_HAS_LLSC
         bool
 
+config CPU_HAS_SMARTMIPS
+        depends on SYS_SUPPORTS_SMARTMIPS
+        bool "Support for the SmartMIPS ASE"
+        help
+          SmartMIPS is a extension of the MIPS32 architecture aimed at
+          increased security at both hardware and software level for
+          smartcards.  Enabling this option will allow proper use of the
+          SmartMIPS instructions by Linux applications.  However a kernel with
+          this option will not work on a MIPS core without SmartMIPS core.  If
+          you don't know you probably don't have SmartMIPS and should say N
+          here.
+
 config CPU_HAS_WB
         bool
 
@@ -1704,6 +1719,9 @@ config CPU_SUPPORTS_HIGHMEM
 config SYS_SUPPORTS_HIGHMEM
         bool
 
+config SYS_SUPPORTS_SMARTMIPS
+        bool
+
 config ARCH_FLATMEM_ENABLE
         def_bool y
         depends on !NUMA