Re: [PATCH 1/7] PM / OPP: Introduce a power estimation helper

[Quentin Perret <quentin.perret@arm.com>]

Hi Viresh,

On Tuesday 29 Jan 2019 at 10:40:30 (+0530), Viresh Kumar wrote:
> > +int of_dev_pm_opp_get_cpu_power(unsigned long *mW, unsigned long *KHz, int cpu)
> 
> I would suggest to change the return type to unsigned long and return 0 for
> errors and positive values for mW.

Well, I can't really do that -- this must match the API of PM_EM:

https://elixir.bootlin.com/linux/v5.0-rc4/source/include/linux/energy_model.h#L62

I'll make sure to make that explicit in the commit message for v2.

> 
> > +{
> > +	unsigned long mV, Hz, MHz;
> 
> MHz is used only once, I think you can get rid of it just open code the division
> by 1000000. Maybe remove Hz as well and directly use kHz.

I would expect/hope the compiler will optimize things like that for me
but yes, I can try to reduce a bit the temp variables if you prefer.

> 
> > +	struct device *cpu_dev;
> > +	struct dev_pm_opp *opp;
> > +	struct device_node *np;
> > +	u32 cap;
> > +	u64 tmp;
> 
> Name this mW with the above changes.

So that doesn't really work given what I mentioned above.

> > +	int ret;
> > +
> > +	cpu_dev = get_cpu_device(cpu);
> > +	if (!cpu_dev)
> > +		return -ENODEV;
> > +
> > +	np = of_node_get(cpu_dev->of_node);
> > +	if (!np)
> > +		return -EINVAL;
> > +
> > +	ret = of_property_read_u32(np, "dynamic-power-coefficient", &cap);
> > +	of_node_put(np);
> > +	if (ret)
> > +		return -EINVAL;
> > +
> > +	Hz = *KHz * 1000;
> > +	opp = dev_pm_opp_find_freq_ceil(cpu_dev, &Hz);
> > +	if (IS_ERR(opp))
> > +		return -EINVAL;
> > +
> > +	mV = dev_pm_opp_get_voltage(opp) / 1000;
> > +	dev_pm_opp_put(opp);
> > +	if (!mV)
> > +		return -EINVAL;
> > +
> > +	MHz = Hz / 1000000;
> > +	tmp = (u64)cap * mV * mV * MHz;
> > +	do_div(tmp, 1000000000);
> > +
> > +	*mW = (unsigned long)tmp;
> > +	*KHz = Hz / 1000;
> > +
> > +	return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(of_dev_pm_opp_get_cpu_power);
> > diff --git a/include/linux/pm_opp.h b/include/linux/pm_opp.h
> > index 0a2a88e5a383..fedde14f5187 100644
> > --- a/include/linux/pm_opp.h
> > +++ b/include/linux/pm_opp.h
> > @@ -322,6 +322,7 @@ int dev_pm_opp_of_get_sharing_cpus(struct device *cpu_dev, struct cpumask *cpuma
> >  struct device_node *dev_pm_opp_of_get_opp_desc_node(struct device *dev);
> >  struct device_node *dev_pm_opp_get_of_node(struct dev_pm_opp *opp);
> >  int of_get_required_opp_performance_state(struct device_node *np, int index);
> > +int of_dev_pm_opp_get_cpu_power(unsigned long *mW, unsigned long *KHz, int cpu);
> >  #else
> >  static inline int dev_pm_opp_of_add_table(struct device *dev)
> >  {
> > @@ -364,6 +365,10 @@ static inline int of_get_required_opp_performance_state(struct device_node *np,
> >  {
> >  	return -ENOTSUPP;
> >  }
> 
> Add a blank line here. We missed adding the same before
> of_get_required_opp_performance_state() earlier, maybe add the new routine
> before of_get_required_opp_performance_state() and add blank line before and
> after it :)

Sounds good !

> 
> > +static inline int of_dev_pm_opp_get_cpu_power(unsigned long *mW, unsigned long *KHz, int cpu)
> > +{
> > +	return -ENOTSUPP;
> > +}
> >  #endif
> >  
> >  #endif		/* __LINUX_OPP_H__ */
> > -- 
> > 2.20.1
> 
> -- 
> viresh

Thanks,
Quentin