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: NLeonid Yegoshin <Leonid.Yegoshin@imgtec.com>
Signed-off-by: NMarkos Chandras <markos.chandras@imgtec.com>

If Config5/LLB is set in the core, then software can write the LLB
bit in the LLADDR register.
Signed-off-by: NMarkos Chandras <markos.chandras@imgtec.com>

The LLBIT (bit 4) in the Config5 CP0 register indicates the software
availability of the Load-Linked bit. This bit is only set by hardware
and it has the following meaning:

0: LLB functionality is not supported
1: LLB functionality is supported. The following feature are also
supported:

- ERETNC instruction. Similar to ERET but it does not clear the LLB
bit in the LLAddr register.
- CP0 LLAddr/LLB bit must be set
- LLbit is software accessible through the LLAddr[0]

This will be used later on to emulate R2 LL/SC instructions.
Signed-off-by: NMarkos Chandras <markos.chandras@imgtec.com>

MIPS R6 uses the <R6 sdc2 opcode for the new BNEZC and JIALC instructions
Signed-off-by: NMarkos Chandras <markos.chandras@imgtec.com>

MIPS R6 uses the <R6 ldc2 opcode for the new BEQZC and JIC instructions
Signed-off-by: NMarkos Chandras <markos.chandras@imgtec.com>

MIPS R6 uses the <R6 swc2 opcode for the new BALC instructions.
Signed-off-by: NMarkos Chandras <markos.chandras@imgtec.com>

MIPS R6 uses the <R6 DADDI opcode for the new BNVC, BNEC and
BNEZLAC instructions.
Signed-off-by: NMarkos Chandras <markos.chandras@imgtec.com>

MIPS R6 uses the <R6 ADDI opcode for the new BOVC, BEQC and
BEQZALC instructions.
Signed-off-by: NMarkos Chandras <markos.chandras@imgtec.com>

MIPS R6 uses the <R6 LWC2 opcode for the new BC instruction.
Signed-off-by: NMarkos Chandras <markos.chandras@imgtec.com>

MIPS R6 added the following four instructions which share the
BGTZ and BGTZL opcode:

BLTZALC: Compact branch-and-link if GPR rt is < to zero
BGTZALC: Compact branch-and-link if GPR rt is > to zero
BLTZL  : Compact branch if GPR rt is < to zero
BGTZL  : Compact branch if GPR rt is > to zero
BLTC   : Compact branch if GPR rs is less than GPR rt
BLTUC  : Similar to BLTC but unsigned
Signed-off-by: NMarkos Chandras <markos.chandras@imgtec.com>

MIPS R6 added the following four instructions which share the
BLEZ and BLEZL opcodes:

BLEZALC: Compact branch-and-link if GPR rt is <= to zero
BGEZALC: Compact branch-and-link if GPR rt is >= to zero
BLEZC  : Compact branch if GPR rt is <= to zero
BGEZC  : Compact branch if GPR rt is >= to zero
BGEC   : Compact branch if GPR rs is less than or equal to GPR rt
BGEUC  : Similar to BGEC but unsigned.
Signed-off-by: NMarkos Chandras <markos.chandras@imgtec.com>

MIPS R6 introduced the following two branch instructions for COP1:

BC1EQZ: Branch if Cop1 (FPR) Register Bit 0 is Equal to Zero
BC1NEZ: Branch if Cop1 (FPR) Register Bit 0 is Not Equal to Zero
Signed-off-by: NMarkos Chandras <markos.chandras@imgtec.com>

MIPS R6 removed the BLTZL, BGEZL, BLTZAL, BGEZAL, BEQL, BNEL, BLEZL,
BGTZL branch likely instructions so we must not try to emulate them on
MIPS R6 if the R2-to-R6 emulator is not present.
Signed-off-by: NMarkos Chandras <markos.chandras@imgtec.com>

The MIPS R6 JR instruction is an alias to the JALR one, so it may
need emulation for non-R6 userlands.
Signed-off-by: NMarkos Chandras <markos.chandras@imgtec.com>

The secondary cache initialization and configuration code is processor
specific so we need to handle MIPS R6 cores as well.
Signed-off-by: NMarkos Chandras <markos.chandras@imgtec.com>

The local_r4k_flush_cache_sigtramp function uses the 'cache'
instruction inside an asm block. However, MIPS R6 changed the
opcode for the cache instruction and as a result of which we
need to set the correct ISA level.
Signed-off-by: NMarkos Chandras <markos.chandras@imgtec.com>

MIPS uses the cpu_has_mips_r2_exec_hazard macro to determine whether the
EHB instruction is available or not. This is necessary for MIPS R6
which also supports the EHB instruction.
Signed-off-by: NLeonid Yegoshin <Leonid.Yegoshin@imgtec.com>
Signed-off-by: NMarkos Chandras <markos.chandras@imgtec.com>

The MIPS R6 pref instruction only has 9 bits for the immediate
field so skip the micro-assembler PREF instruction if the offset
does not fit in 9 bits. Moreover, bit 30 (Pref_PrepareForStore) is
no longer valid in MIPS R6, so we change the default for all MIPS R6
processors to bit 5 (Pref_StoreStreamed).
Signed-off-by: NMarkos Chandras <markos.chandras@imgtec.com>

MIPS R6 dropped the unaligned load and store instructions so
we need to re-write this part of the code for R6 to store
one byte at a time.
Signed-off-by: NLeonid Yegoshin <Leonid.Yegoshin@imgtec.com>
Signed-off-by: NMarkos Chandras <markos.chandras@imgtec.com>

MIPS R6 does not support the unaligned load and store instructions
so we add a special MIPS R6 case to copy one byte at a time if we
need to read/write to unaligned memory addresses.
Signed-off-by: NLeonid Yegoshin <Leonid.Yegoshin@imgtec.com>
Signed-off-by: NMarkos Chandras <markos.chandras@imgtec.com>

MIPS R6 changed the opcodes for LL/SC instructions so we need to set
the appropriate ISA level.

Cc: Matthew Fortune <Matthew.Fortune@imgtec.com>
Signed-off-by: NMarkos Chandras <markos.chandras@imgtec.com>

The load/store unaligned instructions have been removed in MIPS R6
so we need to re-implement the related macros using the regular
load/store instructions. Moreover, the load/store from coprocessor 2
instructions have been reallocated in Release 6 so we will handle them
in the emulator instead.
Signed-off-by: NLeonid Yegoshin <Leonid.Yegoshin@imgtec.com>
Signed-off-by: NMarkos Chandras <markos.chandras@imgtec.com>

The "addi" instruction will trap on overflows which is not something
we need in this code, so we replace that with "addiu".

Link: http://www.linux-mips.org/archives/linux-mips/2015-01/msg00430.html
Cc: Maciej W. Rozycki <macro@linux-mips.org>
Cc: <stable@vger.kernel.org> # v3.15+
Cc: Paul Burton <paul.burton@imgtec.com>
Signed-off-by: NMarkos Chandras <markos.chandras@imgtec.com>

The jr instruction opcode has changed in R6 so make sure
the correct ISA level is set prior using that instruction.
Signed-off-by: NMarkos Chandras <markos.chandras@imgtec.com>

Add the MIPS R6 related preprocessor definitions for FPU signal
related functions. MIPS R6 only has FR=1 so avoid checking that
bit on the C0/Status register.
Signed-off-by: NLeonid Yegoshin <Leonid.Yegoshin@imgtec.com>
Signed-off-by: NMarkos Chandras <markos.chandras@imgtec.com>

Add the MIPS R6 related preprocessor definitions for save/restore
FPU related functions. We also set the appropriate ISA level
so the final return instruction "jr ra" will produce the correct
opcode on R6.
Signed-off-by: NLeonid Yegoshin <Leonid.Yegoshin@imgtec.com>
Signed-off-by: NMarkos Chandras <markos.chandras@imgtec.com>

Add MIPS R6 support to cache and ftlb exceptions, as well as
to the hwrena and ebase register configuration.
Signed-off-by: NLeonid Yegoshin <Leonid.Yegoshin@imgtec.com>
Signed-off-by: NMarkos Chandras <markos.chandras@imgtec.com>

Print 'mips64r6' and/or 'mips32r6' if the kernel is running on
a MIPS R6 core.
Signed-off-by: NMarkos Chandras <markos.chandras@imgtec.com>

The instruction hazard barrier in the form of:

jr.hb	ra
nop

is valid on MIPS R6 as well.
Signed-off-by: NMarkos Chandras <markos.chandras@imgtec.com>

Add MIPS R6 support when decoding the config0 c0 register.
Also add MIPS R6 support when examining the ebase c0 register
to get the core number and when getting the shadow set number
from the srsctl c0 register.
Signed-off-by: NLeonid Yegoshin <Leonid.Yegoshin@imgtec.com>
Signed-off-by: NMarkos Chandras <markos.chandras@imgtec.com>

Just like MIPS R2, in MIPS R6 it is possible to determine if a
timer interrupt has happened or not.
Signed-off-by: NLeonid Yegoshin <Leonid.Yegoshin@imgtec.com>
Signed-off-by: NMarkos Chandras <markos.chandras@imgtec.com>

The current HW bugs checked in cpu-bugs64, do not apply to R6 cores
and they cause compilation problems due to removed <R6 instructions,
so do not check for them for the time being.
Reviewed-by: NMaciej W. Rozycki <macro@linux-mips.org>
Signed-off-by: NLeonid Yegoshin <Leonid.Yegoshin@imgtec.com>
Signed-off-by: NMarkos Chandras <markos.chandras@imgtec.com>

MIPS R6 changed the opcodes for LL/SC instructions so we need to set
the appropriate ISA level.

Cc: Matthew Fortune <Matthew.Fortune@imgtec.com>
Signed-off-by: NMarkos Chandras <markos.chandras@imgtec.com>

"sub $reg, imm" is not a real MIPS instruction. The assembler can
replace that with "addi $reg, -imm". However, addi has been removed
from R6, so we replace the "sub" instruction with the "addiu" one.
Signed-off-by: NMarkos Chandras <markos.chandras@imgtec.com>

MIPS R6 changed the opcodes for LL/SC instructions so we need to set
the appropriate ISA level.

Cc: Matthew Fortune <Matthew.Fortune@imgtec.com>
Signed-off-by: NMarkos Chandras <markos.chandras@imgtec.com>

MIPS R6 changed the opcodes for LL/SC instructions so we need to set
the correct ISA level.

Cc: Matthew Fortune <Matthew.Fortune@imgtec.com>
Signed-off-by: NMarkos Chandras <markos.chandras@imgtec.com>

MIPS R6 changed the opcodes for LL/SC instructions so we need to
set the correct ISA level.

Cc: Matthew Fortune <Matthew.Fortune@imgtec.com>
Signed-off-by: NMarkos Chandras <markos.chandras@imgtec.com>

MIPS R6 changed the opcodes for LL/SC instructions so we need to set
the correct ISA.

Cc: Matthew Fortune <Matthew.Fortune@imgtec.com>
Signed-off-by: NMarkos Chandras <markos.chandras@imgtec.com>

GCC versions supporting MIPS R6 use the ZC constraint to enforce a
9-bit offset for MIPS R6. We will use that for all MIPS R6 LL/SC
instructions.

Cc: Matthew Fortune <Matthew.Fortune@imgtec.com>
Signed-off-by: NMarkos Chandras <markos.chandras@imgtec.com>

The GCC_OFF12_ASM macro is used for 12-bit immediate constrains
but we will also use it for 9-bit constrains on MIPS R6 so we
rename it to something more appropriate.

Cc: Maciej W. Rozycki <macro@linux-mips.org>
Signed-off-by: NMarkos Chandras <markos.chandras@imgtec.com>