On 08 July 2021 09:21, Primoz Fiser wrote:
> Proper machine resets via da9062/da9063 PMICs are very tricky as they
> require special i2c atomic transfers when interrupts are not available
> anymore. This is also a reason why both PMIC's restart handlers do not
> use regmap but instead opt for i2c_smbus_write_byte_data() which does
> i2c transfer in atomic manner. Under the hood, this function tries to
> obtain i2c bus lock with call to i2c_adapter_trylock_bus() which will
> return -EAGAIN (-11) if lock is not available.
>
> Since commit 982bb70517aef ("watchdog: reset last_hw_keepalive time at
> start") occasional restart handler failures with "Failed to shutdown
> (err = -11)" error messages were observed, indicating that some
> process is holding the i2c bus lock. Investigation into the matter
> uncovered that sometimes during reboot sequence watchdog ping is issued
> late into poweroff/reboot phase which did not happen before mentioned
> commit (usually the watchdog ping happened immediately as commit message
> suggests). As of now, when watchdog ping usually happens late into
> poweroff/reboot stage when interrupts are not available anymore, i2c bus
> lock cannot be released anymore and pending restart handler in turn
> fails.
>
> Thus, to prevent such late watchdog pings from happening ahead of
> pending machine restart and consequently locking up the i2c bus, check
> for system_state in watchdog ping handler and consequently do not send
> pings anymore in case system_state > SYSTEM_RUNNING.
>
> Signed-off-by: Primoz Fiser <primoz.fiser@xxxxxxxxx>
Reviewed-by: Adam Thomson <Adam.Thomson.Opensource@xxxxxxxxxxx>
