RE: [PATCH v2 04/12] i2c: riic: Use pm_runtime_resume_and_get()

[Biju Das]

Hi Andi and Claudiu,

> -----Original Message-----
> From: Andi Shyti <andi.shyti@xxxxxxxxxx>
> 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


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