While testing "arc: make sure _start is in the beginning of .text
section" I haven't done proper clean-up of built binaries and so missed
another tiny bit that lead to the following error:
 --->8---
    LD      u-boot
 arc-linux-ld.bfd: cannot find arch/arc/lib/start.o
 Makefile:1107: recipe for target 'u-boot' failed
 make: *** [u-boot] Error 1
 --->8---

Fix is trivial: put "start.o" in "extra-y".

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

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>

ARCv2 cores may have built-in SLC (System Level Cache, AKA L2-cache).
This change adds functions required for controlling SLC:
 * slc_enable/disable
 * slc_flush/invalidate

For now we just disable SLC to escape DMA coherency issues until either:
 * SLC flush/invalidate is supported in DMA APIin U-Boot
 * hardware DMA coherency is implemented (that might be board specific
   so probably we'll need to have a separate Kconfig option for
   controlling SLC explicitly)

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

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Simon Glass <sjg@chromium.org>

Now when all infrastructure in ARC is ready for it let's switch ARC UART
to driver model.

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Simon Glass <sjg@chromium.org>

 [1] Fix misspeling in ARC_CACHE_LINE_SHIFT dependency, now cache-line
lenth selection is correctly enabled if either I$ or D$ are enabled.

 [2] Add dummy entry to target list to make sure target type is always
mentioned in defconfig. Otherwise defconfig for the first target in the
list will not have target name and later on with addition of the new
target on top of the list in Kconfig will lead to corrupted
configuration expanded from defconfig.

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

As discussed on mailing list we're drifting away from
CONFIG_SYS_GENERIC_GLOBAL_DATA in favour to use of board_init_f_mem()
for global data.

So do this for ARC architecture.

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

Intention behind this work was elimination of as much assembly-written
code as it is possible.

In case of ARC we already have relocation fix-up implemented in C so why
don't we use C for U-Boot copying, .bss zeroing etc.

It turned out x86 uses pretty similar approach so we re-used parts of
code in "board_f.c" initially implemented for x86.

Now assembly usage during init is limited to stack- and frame-pointer
setup before and after relocation.

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
Cc: Simon Glass <sjg@chromium.org>

This separation makes maintenance of code easier because those low-level
interrupt- or exception handling routines are pretty static and usually
require not much care while start-up code is a subject of modifications
and enhancements.

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>