linux-kernel - Re: [PATCH v3 2/3] clk: qcom: lpass-sc7180: Disentangle the two clock devices

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Date:   Wed, 14 Oct 2020 17:10:51 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Stephen Boyd <sboyd@...nel.org>
Cc:     Taniya Das <tdas@...eaurora.org>,
        "ARM/QUALCOMM SUPPORT" <linux-soc@...r.kernel.org>,
        David Brown <david.brown@...aro.org>,
        Rajendra Nayak <rnayak@...eaurora.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Michael Turquette <mturquette@...libre.com>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        linux-clk <linux-clk@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 2/3] clk: qcom: lpass-sc7180: Disentangle the two clock devices

Hi,

On Wed, Oct 14, 2020 at 4:33 PM Stephen Boyd <sboyd@...nel.org> wrote:
>
> Quoting Doug Anderson (2020-10-14 16:07:52)
> > Hi,
> >
> > On Wed, Oct 14, 2020 at 4:00 PM Stephen Boyd <sboyd@...nel.org> wrote:
> > >
> > > Quoting Doug Anderson (2020-10-14 15:28:58)
> > > > Hi,
> > > >
> > > > On Wed, Oct 14, 2020 at 3:10 PM Stephen Boyd <sboyd@...nel.org> wrote:
> > > > >
> > > > > Quoting Douglas Anderson (2020-10-14 14:05:22)
> > > > > > diff --git a/drivers/clk/qcom/lpasscorecc-sc7180.c b/drivers/clk/qcom/lpasscorecc-sc7180.c
> > > > > > index abcf36006926..48d370e2108e 100644
> > > > > > --- a/drivers/clk/qcom/lpasscorecc-sc7180.c
> > > > > > +++ b/drivers/clk/qcom/lpasscorecc-sc7180.c
> > > > > > @@ -356,12 +356,48 @@ static const struct qcom_cc_desc lpass_audio_hm_sc7180_desc = {
> > > > > >         .num_gdscs = ARRAY_SIZE(lpass_audio_hm_sc7180_gdscs),
> > > > > >  };
> > > > > >
> > > > > > +static void lpass_pm_runtime_disable(void *data)
> > > > > > +{
> > > > > > +       pm_runtime_disable(data);
> > > > > > +}
> > > > > > +
> > > > > > +static void lapss_pm_clk_destroy(void *data)
> > > > > > +{
> > > > > > +       pm_clk_destroy(data);
> > > > > > +}
> > > > >
> > > > > Why are these helpers added again? And do we even need them? Can't we
> > > > > just pass pm_runtime_disable or pm_clk_destroy to the
> > > > > devm_add_action_or_reset() second parameter?
> > > >
> > > > Unfortunately, we can't due to the C specification.  Take a look at
> > > > all the other users of devm_add_action_or_reset() and they all have
> > > > pretty much the same stupid thing.
> > >
> > > Ok, but we don't need two of the same functions, right?
> >
> > How would you write it more cleanly?
>
> Oh I see I'm making it confusing. Patch 1 has two functions for
> pm_runtime_disable() and pm_clk_destroy(), called
> lpass_pm_runtime_disable() and lapss_pm_clk_destroy() respectively
> (please fix the lapss typo regardless).

Oops, sorry for the typo.


> Then this patch seems to introduce them again, but really the diff is
> getting confused and it looks like the functions are introduced again.
> Can you move them to this location (or at least near it) in the first
> patch so that this doesn't look like they're being introduced again?

Yeah.  v4 coming up soon then.


> > > > ...actually, do we even need the runtime_disable in the error path?
> > > > When the dev goes away does it matter if you left pm_runtime enabled
> > > > on it?
> > > >
> > >
> > > I don't know. The device isn't destroyed but maybe when the driver is
> > > unbound it resets the runtime PM counters?
> >
> > Certainly it seems safest just to do it...
> >
>
> Can you confirm? I'd rather not carry extra code.

Confirmed that we need it.  Specifically from
"Documentation/power/runtime_pm.rst"

> Drivers in ->remove() callback should undo the runtime PM changes done
> in ->probe(). Usually this means calling pm_runtime_disable(),
> pm_runtime_dont_use_autosuspend() etc.

It's my assertion that having it in devm is as good as having it in
the remove() callback because devres_release_all() follows the
remove() calls in base/dd.c