linux-kernel - Re: [PATCH v2 04/12] i2c: riic: Use pm_runtime_resume_and

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Date: Wed, 26 Jun 2024 09:10:51 +0200
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Biju Das <biju.das.jz@...renesas.com>
Cc: "Claudiu.Beznea" <claudiu.beznea@...on.dev>, Chris Brandt <Chris.Brandt@...esas.com>, 
	"andi.shyti@...nel.org" <andi.shyti@...nel.org>, "robh@...nel.org" <robh@...nel.org>, 
	"krzk+dt@...nel.org" <krzk+dt@...nel.org>, "conor+dt@...nel.org" <conor+dt@...nel.org>, 
	"magnus.damm@...il.com" <magnus.damm@...il.com>, "mturquette@...libre.com" <mturquette@...libre.com>, 
	"sboyd@...nel.org" <sboyd@...nel.org>, "p.zabel@...gutronix.de" <p.zabel@...gutronix.de>, 
	"wsa+renesas@...g-engineering.com" <wsa+renesas@...g-engineering.com>, 
	"linux-renesas-soc@...r.kernel.org" <linux-renesas-soc@...r.kernel.org>, 
	"linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>, 
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, 
	"linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>, 
	Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
Subject: Re: [PATCH v2 04/12] i2c: riic: Use pm_runtime_resume_and_get()

Hi Biju,

On Wed, Jun 26, 2024 at 8:23 AM Biju Das <biju.das.jz@...renesas.com> wrote:
> > From: claudiu beznea <claudiu.beznea@...on.dev>
> > On 25.06.2024 18:53, Biju Das wrote:
> > >> From: Claudiu <claudiu.beznea@...on.dev>
> > >> From: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
> > >>
> > >> pm_runtime_get_sync() may return with error. In case it returns with
> > >> error
> > >> dev->power.usage_count needs to be decremented.
> > >> dev->pm_runtime_resume_and_get()
> > >> takes care of this. Thus use it.
> > >>
> > >> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>

> > >> -  pm_runtime_get_sync(dev);
> > >> +  ret = pm_runtime_resume_and_get(dev);
> > >> +  if (ret) {
> > >> +          dev_err(dev, riic_rpm_err_msg);
> > >
> > > As at the moment we don't know how to reproduce this error condition
> > > Can we use WARN_ON_ONCE() instead to catch detailed error condition here??
> >
> > [1] states "So, naturally, use of WARN_ON() is also now discouraged much of the time". I've go with
> > dev_err() or something similar.
>
> WARN_ON_ONCE() should be ok I guess as people are using for printing this info only once??
>
> Currently we don't know how to trigger pm_runtime_resume_and_get() error
> condition in our setup using a testapp and we are expecting an error may
> happen in future. If at all there is an error in future, we need detailed
> error info so that we can handle it and fix the bug.

On Renesas systems, pm_runtime_resume_and_get() never fails.
That's the reason why originally we didn't care to check the return
value of pm_runtime_get_sync().

The various janitors disagreed, causing cascaded changes all over
the place...

IMHO, WARN_ON_ONCE() is definitely overkill, only bloating the code.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds