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

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Message-ID:
 <TY3PR01MB113460F680BFDFC3A15763DC086DA2@TY3PR01MB11346.jpnprd01.prod.outlook.com>
Date: Mon, 8 Jul 2024 09:33:49 +0000
From: Biju Das <biju.das.jz@...renesas.com>
To: Andi Shyti <andi.shyti@...nel.org>, Claudiu.Beznea
	<claudiu.beznea@...on.dev>
CC: Chris Brandt <Chris.Brandt@...esas.com>, "robh@...nel.org"
	<robh@...nel.org>, "krzk+dt@...nel.org" <krzk+dt@...nel.org>,
	"conor+dt@...nel.org" <conor+dt@...nel.org>, "geert+renesas@...der.be"
	<geert+renesas@...der.be>, "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()



> -----Original Message-----
> From: Biju Das
> Sent: Monday, July 8, 2024 6:37 AM
> Subject: RE: [PATCH v2 04/12] i2c: riic: Use pm_runtime_resume_and_get()
> 
> Hi Andi and Claudiu,
> 
> > -----Original Message-----
> > From: Andi Shyti <andi.shyti@...nel.org>
> > Sent: Thursday, July 4, 2024 11:43 PM
> > Subject: Re: [PATCH v2 04/12] i2c: riic: Use
> > pm_runtime_resume_and_get()
> >
> > Hi Claudiu,
> >
> > > diff --git a/drivers/i2c/busses/i2c-riic.c
> > > b/drivers/i2c/busses/i2c-riic.c index 83e4d5e14ab6..002b11b020fa
> > > 100644
> > > --- a/drivers/i2c/busses/i2c-riic.c
> > > +++ b/drivers/i2c/busses/i2c-riic.c
> > > @@ -113,6 +113,8 @@ struct riic_irq_desc {
> > >  	char *name;
> > >  };
> > >
> > > +static const char * const riic_rpm_err_msg = "Failed to runtime
> > > +resume";
> >
> > Please, don't do this. Much clearer to write the message explicitly.
> >
> > > +
> > >  static inline void riic_writeb(struct riic_dev *riic, u8 val, u8
> > > offset)  {
> > >  	writeb(val, riic->base + riic->info->regs[offset]); @@ -133,10
> > > +135,14 @@ static int riic_xfer(struct i2c_adapter *adap, struct
> > > +i2c_msg msgs[], int num)
> > >  	struct riic_dev *riic = i2c_get_adapdata(adap);
> > >  	struct device *dev = adap->dev.parent;
> > >  	unsigned long time_left;
> > > -	int i;
> > > +	int i, ret;
> > >  	u8 start_bit;
> > >
> > > -	pm_runtime_get_sync(dev);
> > > +	ret = pm_runtime_resume_and_get(dev);
> >
> > In principle I like the error message to be always checked and I will
> > always approve it. Whenever there is a return value, even when we are sure it's always '0', it
> needs to be checked.
> >
> > I had lots of discussions in the past about this topic but I haven't
> > always found support. I'd love to have the ack from a renesas maintainer here.
> >
> > > +	if (ret) {
> 
> Checking ret will lead to imbalance. It should be ret < 0 as ret = 1 corresponds to RPM_ACTIVE and
> the API does not call put() when ret = 1; see [1] and [2]
> 
> [1] https://elixir.bootlin.com/linux/v6.10-rc6/source/drivers/base/power/runtime.c#L778
> 
> [2] https://elixir.bootlin.com/linux/v6.10-rc6/source/include/linux/pm_runtime.h#L431

I got confused. the code for pm_runtime_resume_and_get() seems correct.
https://elixir.bootlin.com/linux/latest/source/include/linux/pm_runtime.h#L436

> 
> 
> Another question, pm_runtime_put [3] can also return error, don't we need to propagate that as well
> to caller??
> 
> [3] https://elixir.bootlin.com/linux/v6.10-rc6/source/drivers/base/power/runtime.c#L1086
> 
> Cheers,
> Biju