On Tue, Dec 10, 2019 at 12:52:30AM +0800, Chuhong Yuan wrote:

> I have a question that what if CONFIG_PM is not defined?
> Since I have met runtime PM before in the patch
> a31eda65ba21 ("net: fec: fix clock count mis-match").
> I learned there that in some cases CONFIG_PM is not defined so runtime PM
> cannot take effect.
> Therefore, undo operations should still exist in remove functions.

There's also the case where runtime PM is there and the device is active
at suspend - it's not that there isn't a problem, it's that we can't
unconditionally do a disable because we don't know if there was a
matching enable.  It'll need to be conditional on the runtime PM state.