From b0a668fb2038d846a466c7a16a358d874002b697 Mon Sep 17 00:00:00 2001
From: Leonid Yegoshin <Leonid.Yegoshin@imgtec.com>
Date: Wed, 3 Dec 2014 15:47:03 +0000
Subject: MIPS: kernel: mips-r2-to-r6-emul: Add R2 emulator for MIPS R6

MIPS R6 removed quite a few R2 instructions. However, there
is plenty of <R6 userland code so we add an in-kernel emulator
so we can still be able to execute all R2 userland out there.

The emulator comes with a handy debugfs under /mips/ directory
(r2-emul-stats) to provide some basic statistics of the
instructions that are being emulated.

Below are some statistics from booting a minimal buildroot image:

Instruction     Total   BDslot
------------------------------
movs            236969  0
hilo            56686   0
muls            55279   0
divs            10941   0
dsps            0       0
bops            1       0
traps           0       0
fpus            0       0
loads           214981  17
stores          103364  0
llsc            56898   0
dsemul          150418  0
jr              370158
bltzl           43
bgezl           1594
bltzll          0
bgezll          0
bltzal          39
bgezal          39
beql            14503
bnel            138741
blezl           0
bgtzl           3988

Signed-off-by: Leonid Yegoshin <Leonid.Yegoshin@imgtec.com>
Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
---
 arch/mips/Kconfig | 13 +++++++++++++
 1 file changed, 13 insertions(+)

(limited to 'arch/mips/Kconfig')

diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index 883eb3aacedf..afa808ab9f44 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -2063,6 +2063,19 @@ config MIPS_MT_FPAFF
 	default y
 	depends on MIPS_MT_SMP
 
+config MIPSR2_TO_R6_EMULATOR
+	bool "MIPS R2-to-R6 emulator"
+	depends on CPU_MIPSR6 && !SMP
+	default y
+	help
+	  Choose this option if you want to run non-R6 MIPS userland code.
+	  Even if you say 'Y' here, the emulator will still be disabled by
+	  default. You can enable it using the 'mipsr2emul' kernel option.
+	  The only reason this is a build-time option is to save ~14K from the
+	  final kernel image.
+comment "MIPS R2-to-R6 emulator is only available for UP kernels"
+	depends on SMP && CPU_MIPSR6
+
 config MIPS_VPE_LOADER
 	bool "VPE loader support."
 	depends on SYS_SUPPORTS_MULTITHREADING && MODULES
-- 
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