linux-kernel - RE: [EXT] Re: [PATCH net v2] net: fec: add a check for CONFIG

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Date:   Wed, 13 Nov 2019 01:50:20 +0000
From:   Andy Duan <fugang.duan@....com>
To:     David Miller <davem@...emloft.net>,
        "hslester96@...il.com" <hslester96@...il.com>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [EXT] Re: [PATCH net v2] net: fec: add a check for CONFIG_PM to
 avoid clock count mis-match

From: David Miller <davem@...emloft.net> Sent: Wednesday, November 13, 2019 3:13 AM
> From: Chuhong Yuan <hslester96@...il.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@...il.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