reset-source: add stub for of_get_reset_source_priority ...

Allow drivers to build even if reset source support isn't built in.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

reset-source: Allow different priorities ...

Different devices may report the reset source with different levels
of certainty. For example a SoC may see a power-on reset, but this
may only be because an external PMIC has power cycled the SoC. This
means the PMIC knows the real reason better and thus the reset reason
from the PMIC should be preferred.

This patch introduces priorities for the reset_source to handle the
above scenario. Also add a of_get_reset_source_priority() function
to retrieve the desired priority from the device tree.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

reset_source: Add external reset ...

Some SoCs have special device pins for external reset signals.

Signed-off-by: Wadim Egorov <w.egorov@phytec.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

reset_source: add thermal reset ...

Some SoCs are able to detect if they got reset
in response to an overtemperature event.

Signed-off-by: Lucas Stach <dev@lynxeye.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

reset_source: add reset_source_get ...

To get reset_source from C code, not only from shell.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

reset_source: rename set_reset_source to reset_source_set ...

To get all reset source related functions into the same function
namespace.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

reset_source: provide static inline function if disabled ...

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

Enable a way to provide the reason for "being here" ...

Many architectures support a way to detect why the bootloader is running.
This patch adds a global variable to be able to use the cause in some kind of
shell code to do special things on demand. For example to do an emergency boot,
when the last boot fails and the watchdog reactivate the hanging system.

Signed-off-by: Juergen Beisert <jbe@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>