This is important to have entry point in the beginning of .text section
because it allows simple loading and execution of U-Boot.

For example pre-bootloader loads U-Boot in memory starting from offset
0x81000000 and then just jumps to the same address.

Otherwise pre-bootloader would need to find-out where entry-point is. In
its turn if it deals with binary image of U-Boot there's no way for
pre-bootloader to get required value.

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>

Even though ARCompact and ARCv2 are not binary compatible most of
assembly instructions are used in both. With this change we'll get rid
of duplicate code.

Still IVTs are implemented differently so we're keeping them in separate
files.

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>

ARC HS and ARC EM are new cores based on ARCv2 ISA which is binary
incompatible with ISAv1 (AKA ARCompact).

Significant difference between ISAv2 and v1 is implementation of
interrupt vector table.

In v1 it is implemented in the same way as on many other architectures -
as a special location where user may put whether code executed in place
(if machine word of space is enough) or jump to a full-scale interrupt
handler.

In v2 interrupt table is just an array of adresses of real interrupt
handlers. That requires a separate section for IVT that is not encoded
as code by assembler.

This change adds support for following cores:
 * ARC EM6 (simple 32-bit microcontroller without MMU)
 * ARC HS36 (advanced 32-bit microcontroller without MMU)
 * ARC HS38 (advanced 32-bit microcontroller with MMU)

As a part of ARC HS38 new version of MMU (v4) was introduced.

Also this change adds AXS131 board which is the same DW ARC SDP base board but
with ARC HS38 CPU tile.

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>

As a preparation to ARCv2 port submission we're moving CPU slection
flags to a common location.
Also it will allow us to have more flexible CPU specification, not only
ISA version but CPU family as well checking CONFIG_ARC_CPU_xxx.

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>

As a preparation to ARCv2 port submission we rename "arc700" folder to
"arcv1" which stands for ARCv1 ISA also known as ARCompact.

This will allow us to add more flavours of binary-compatible ARCv1 CPUs
like ARC600 if needed later on and all required ARCv2 CPUs (which are
binary incompatible with ARCv1) in "arcv2" folder in subsequent commits.

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
Signed-off-by: Igor Guryanov <guryanov@synopsys.com>

"reset.c" and "cpu.c" have no architecture-specific code at all.
Others are applicable to either ARC CPU.

This change is a preparation to submission of ARCv2 architecture port.

Even though ARCv1 and ARCv2 ISAs are not binary compatible most of
built-in modules still have the same programming model - AUX registers
are mapped in the same addresses and hold the same data (new featues
extend existing ones).

So only low-level assembly code (start-up, interrupt handlers) is left
as CPU(actually ISA)-specific. This significantyl simplifies maintenance
of multiple CPUs/ISAs.

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
Signed-off-by: Igor Guryanov <guryanov@synopsys.com>

This way we'll be able to use the same one script for either ARC CPU.

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>

Even though existing implementation works fine in preparation to
submission of ARCv2 architecture we need this change.

In case of ARCv2 interrupt vector table consists of just addresses
of corresponding handlers. And if those addresses will be in .text
section then assembler will encode them as everything in .text section
as middle-endian and then on real execution CPU will read swapped
addresses and will jump into the wild.

Once introduced new section is situated so .text section remains the
first which allows us to use common linker option for linking everything
to a specified CONFIG_SYS_TEXT_BASE.

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
Signed-off-by: Igor Guryanov <guryanov@synopsys.com>

Depending on MMU presence in CPU there're differences in HW behavior.
For example address of instruction that caused exception is put in
ECR register if MMU exists and in ERET register otherwise.

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
Signed-off-by: Igor Guryanov <guryanov@synopsys.com>

To disable interrupts we need to reset corresponding flags in STATUS32
register. For this we need to OR flags for interrupts level1 and level2
and then AND with current value in STATUS32.

Before that implementation was incorrect.

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
Signed-off-by: Igor Guryanov <guryanov@synopsys.com>