Add a thread framework test to the lib tests. Update the API
documentation to use the test as an example.

Signed-off-by: Jerome Forissier <jerome.forissier@linaro.org>
Acked-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>

Add a new internal API called uthread (Kconfig symbol: UTHREAD) which
provides cooperative multi-tasking. The goal is to be able to improve
the performance of some parts of U-Boot by overlapping lengthy
operations, and also implement background jobs in the U-Boot shell.
Each uthread has its own stack allocated on the heap. The default stack
size is defined by the UTHREAD_STACK_SIZE symbol and is used when
uthread_create() receives zero for the stack_sz argument.

The implementation is based on context-switching via initjmp()/setjmp()/
longjmp() and is inspired from barebox threads [1]. A notion of thread
group helps with dependencies, such as when a thread needs to block
until a number of other threads have returned.

The name "uthread" comes from "user-space threads" because the
scheduling happens with no help from a higher privileged mode, contrary
to more complex models where kernel threads are defined. But the 'u'
may as well stand for 'U-Boot' since the bootloader may actually be
running at any privilege level and the notion of user vs. kernel may
not make much sense in this context.

[1] https://github.com/barebox/barebox/blob/master/common/bthread.c

Signed-off-by: Jerome Forissier <jerome.forissier@linaro.org>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>

Test the initjmp() function when HAVE_INITJMP is set. Use the test as an
example in the API documentation.

Signed-off-by: Jerome Forissier <jerome.forissier@linaro.org>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>

Add the HAVE_INIJMP symbol to be set by architectures that support
initjmp(), a non-standard extension to setjmp()/longjmp() allowing to
initialize a jump buffer with a function pointer and a stack pointer.
This will be useful to later introduce threads. With this new function
it becomes possible to longjmp() to a particular function pointer
(rather than to a point previously reached during program execution as
is the case with setjmp()), and with a custom stack. Both things are
needed to spin off a new thread. Then the usual setjmp()/longjmp() pair
is enough to save and restore a context, i.e., switch thread.

Add the initjmp() prototype to <include/setjmp.h> since it is common to
all architectures.

Add an entry to the API documentation: doc/api/setjmp.rst.

Signed-off-by: Jerome Forissier <jerome.forissier@linaro.org>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>

Add include/fs.h to the API documentation.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>

Introduce simple led.rst documentation to document all the additional
Kconfig and the current limitation of LED_BLINK and GPIO software blink.

Also add missing definition for sw_blink in led_uc_plat struct.

Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

The bootcount documentation was using "unattended" while it probably
intending to say "unintended"

Signed-off-by: Vasileios Amoiridis <vasileios.amoiridis@cern.ch>
Reviewed-by: Quentin Schulz <quentin.schulz@cherry.de>

Move to the new documentation style with rST formatting.

Signed-off-by: Vasileios Amoiridis <vasileios.amoiridis@cern.ch>

If CSRs like seed are readable by S-mode, may not be determinable by
S-mode. For safe driver probing allow to resume via a longjmp after an
exception.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Leo Yu-Chi Liang <ycliang@andestech.com>

Add the events.h include to the API documentation.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Simon Glass <sjg@chromium.org>