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SubjectRE: [EXT] Re: [PATCH net v2] net: fec: add a check for CONFIG_PM to avoid clock count mis-match
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From: David Miller <davem@davemloft.net> Sent: Wednesday, November 13, 2019 3:13 AM
> From: Chuhong Yuan <hslester96@gmail.com>
> Date: Tue, 12 Nov 2019 19:28:30 +0800
>
> > If CONFIG_PM is enabled, runtime pm will work and call runtime_suspend
> > automatically to disable clks.
> > Therefore, remove only needs to disable clks when CONFIG_PM is disabled.
> > Add this check to avoid clock count mis-match caused by double-disable.
> >
> > Fixes: c43eab3eddb4 ("net: fec: add missed clk_disable_unprepare in
> > remove")
> > Signed-off-by: Chuhong Yuan <hslester96@gmail.com>
>
> I don't understand this at all.
>
> The clk disables here match the unconditional clk enables in the probe
> function.
>
> And that is how this is supposed to work, probe enables match remove
> disables. And suspend disables match resume enables.
>
> Why isn't the probe enable taking the correct count, which the remove
> function must match with an appropriate disable? There is no CONFIG_PM
> guarding the probe time clk enables.

Current driver runtime pm callback enable/disable clk_ipg/clk_ahb two clks.
CONFIG_PM is a optional config, if CONFIG_PM is disabled, runtime callbacks will
Not be called.
The driver enable clk_ipg/clk_ahb two clks during probe, and depends runtime
suspend to disable the two clks if CONFIG_PM is enabled.

In driver remove() also need to disable the two clks if CONIFG_PM is disabled.
So the patch c43eab3eddb4 ("net: fec: add missed clk_disable_unprepare in emove")
target the fixes if CONFIG_PM is not enabled, but the patch ignore to check the
CONFIG_PM that make clock count mismatch in CONFIG_PM enabled case.

Andy

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