At present the debug UART is only set up in SPL, on the assumption that
the boot flow will always pass through there. When booting from coreboot,
SPL is not used, so the debug UART is not available.

Move the code into a common place so that it can be used in U-Boot proper
also. Add the required init to start_from_spl.S as well.

Signed-off-by: Simon Glass <sjg@chromium.org>

With chromebook_coral we normally run TPL->SPL->U-Boot. This is the
'bare metal' case.

When running from coreboot we put u-boot.bin in the RW_LEGACY portion
of the image, e.g. with:

   cbfstool image-coral.serial.bin add-flat-binary -r RW_LEGACY \
	-f /tmp/b/chromebook_coral/u-boot.bin -n altfw/u-boot \
	-c lzma -l 0x1110000 -e 0x1110000

In this case U-Boot is run from coreboot (actually Depthcharge, its
payload) so we cannot access CAR. Use the existing stack instead.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

At present we call spl_init() before identifying the CPU. This is not a
good idea - e.g. if bootstage is enabled then it will try to set up the
timer which works better if the CPU is identified.

Put explicit code at each entry pointer to identify the CPU.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

The full start-up sequence (TPL->SPL->U-Boot) can be a bit confusing since
each phase has its own 'start' file. Add comments to explain this.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

When a previous phase of U-Boot has run we need to adjust the init of
subsequent states to avoid messing up the CPU state.

Add a new version of the start logic for SPL, when it boots from TPL
(start_from tpl.c) and a new version for U-Boot when it boots from SPL.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>