xtensa: smp: add headers for missing function prototypes

Use <asm/smp.h> to provide the prototype for secondary_start_kernel().
Use <linux/profile.h> to provide the prototype for
setup_profiling_timer().

arch/xtensa/kernel/smp.c:119:6: warning: no previous prototype for 'secondary_start_kernel' [-Wmissing-prototypes]
119 | void secondary_start_kernel(void)
arch/xtensa/kernel/smp.c:461:5: warning: no previous prototype for 'setup_profiling_timer' [-Wmissing-prototypes]
461 | int setup_profiling_timer(unsigned int multiplier)

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Chris Zankel <chris@zankel.net>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Message-Id: <20230920052139.10570-11-rdunlap@infradead.org>
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

xtensa/cpu: Mark cpu_die() __noreturn

cpu_die() doesn't return. Annotate it as such. By extension this also
makes arch_cpu_idle_dead() noreturn.

Acked-by: Max Filippov <jcmvbkbc@gmail.com>
Link: https://lore.kernel.org/r/ad801544cab7c26a0f3bbf7cfefb67303f4cd866.1676358308.git.jpoimboe@kernel.org
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>

xtensa: implement CPU hotplug

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Chris Zankel <chris@zankel.net>

xtensa: add SMP support

This is largely based on SMP code from the xtensa-2.6.29-smp tree by
Piet Delaney, Marc Gauthier, Joe Taylor, Christian Zankel (and possibly
other Tensilica folks).

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Chris Zankel <chris@zankel.net>

xtensa: move headers files to arch/xtensa/include

Move all header files for xtensa to arch/xtensa/include and platform and
variant header files to the appropriate arch/xtensa/platforms/ and
arch/xtensa/variants/ directories.

Moving the files gets also rid of all uses of symlinks in the Makefile.

This has been completed already for the majority of the architectures
and xtensa is one out of six missing.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Chris Zankel <chris@zankel.net>