[PATCH] drivers: power: reset: at91-reset: Provide reset reason via sysfs (amended with Signed-off-by tag)

On 27/01/2016 at 08:14:21 +0100, Sebastian Reichel wrote :

I can see, that there are currently six different values possible
for at91-reset, but it's unclear to me what some of them mean, so
that should be covered in the ABI documentation. Also it may make
sense to drop the reset suffix for some of them (e.g. "unknown").

    reason = "general reset";

    This is power-on by power-button/applying voltage?

Yes

    reason = "wakeup";

    This is power-on by RTC?

This can actually be any wakeup, but most likely RTC but it could also
be triggered by an external PMIC. Atmel's definition is general: both
VDDcore and VDDbu are rising, wakeup: only VDDcore is rising

    reason = "watchdog reset";

    I gues this is reboot triggered by watchdog timeout?

Yes

    reason = "software reset";

    This will be returned if system was started by rebooting via
    "reboot / shutdown -r"?

This will be the case yes

    reason = "user reset";

    This is returned if the board's reset button was pressed?

Reset button or any signal on the reset pin of the SoC

    reason = "unknown reset";

    => just use "unknown"

It should not happen anyway :)

I suggest to create include/linux/power/power_on_reason.h, with
standardized values, that are used by the driver:

#define POWER_ON_REASON_RTC "RTC wakeup"
#define POWER_ON_REASON_WATCHDOG "watchdog timeout"
...

-- 
Alexandre Belloni, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com