Hi,
I have an TI am335x that is using a i2c PMIC with pm_power_off hook
which locks up on shutdown. The pm_power_off hook gets stuck obtaining
i2c_lock_adapter(). The holder of the lock is the lis3lv02d
accelerometer which never releases it.
I do not think there is an issue in lis3lv02d. I think this is a general
issue with i2c since other drivers have the same design. What I don't
have is clear understanding of if/when/how i2c_transfer() can be called
post kernel_power_off(). Is it possible to call i2c_transfer() at this
point. I have tried calling schedule() and msleep() inside of
kernel_power_off() after syscore_shutdown(). It looks like interrupts
are enabled and I can still schedule at this point. So how is it
possible that lis3lv02d is never able to exit the i2c_transfer()? Is
there some other lock inside i2c_transfer that it is blocking on?
Is it possible that the process which had the accelerometer open has
exited while holding the i2c lock. Is it even possible for a device to
shutdown or file to close while holding a lock in the kernel?
I looked at adding a lis3lv02d_i2c_shutdown, but that was too late in
the process already and the lis3lv02d was already stuck. Is there a very
early place during shutdown that I can kick everyone off the i2c bus?
Obviously this might not be the best general solution, but my concern
right now is fixing the problem on this particular system first.
-James
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