reset: stm32: migrate restart reason and handler from stm32_iwdg ...

The watchdog driver will remain unprobed if the driver or the OF node
is disabled, but the reset reason is useful even then.

System reset and reset source determination is achieved with the RCC
peripheral for which we have a reset controller driver.
Move the code over there, so reset reason and reset are available
always.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

reset_source: migrate from reset_source_name to reset_source_to_string ...

Whether reset_source_name() returns the just set reset_source is
dependent on probe order and the priorities of prior reset sources
in relation to the current one. Make this more robust by using the new
reset_source_to_string.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

Merge branch 'for-next/watchdog'

watchdog: stm32_iwdg: explicitly set .running to UNSUPPORTED ...

I've spent some time trying to get the ONF (Watchdog enable status)
bit in the IWDG_SR register to read as something other than zero.

It has since been confirmed to be non-functional[1]. To avoid someone
else spending time on this, document that running status is unsupported
on this hardware explicitly.
No functional change as UNSUPPORTED is already the default.

[1]: https://www.spinics.net/lists/arm-kernel/msg770527.html

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

watchdog: stm32_iwdg: return -ENOSYS on attempt to disable ...

The stm32_iwdg watchdog can't be disabled. To have the wd commant report
this fact correctly to the user, the ->set_timeout needs to return -ENOSYS
which is interpreted as "Watchdog cannot be disabled" instead of -EINVAL
which means "Timeout value out of range".

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

watchdog: remove wrong uses of timeout_cur ...

The barebox watchdog poller uses the struct watchdog.timeout_cur as
the timeout value to configure the watchdog with.

There's no need for the device driver to set this. I didn't know that
when I wrote the drivers, but I do now, hence this commit.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

reset_source: drop reset_source_set_instance() ...

The semantic of reset_source_set_instance() required a separate call to
reset_source_set() (or reset_source_set_priority()) and checked right
usage only using the type. Make the set of functions a bit easier to use
by dropping reset_source_set_instance() and instead introduce a function
that can set all relevant parameters (source, priority and instance) in
one go.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

watchdog: stm32_iwdg: remove left-over comment ...

The reset reason part of the code is based on the i.MX6's and duplicated
a comment from there, which isn't applicable to the STM32. Delete it.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

watchdog: add stm32 watchdog and reset driver ...

The driver supports setting watchdog timeout, system reset
and querying reset reason. Disabling watchdog isn't possible
in hardware, thus users should either only enable it before
boot or have the poller take care of feeding it.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>