Re: [PATCH v2] thermal: devfreq_cooling: Use PM QoS to set frequency limits

[Matthias Kaehlcke]

Is any further action needed from my side or can this land?

Thanks

Matthias

On Fri, Jan 17, 2020 at 02:22:02PM +0900, Chanwoo Choi wrote:
> On 1/17/20 8:12 AM, Matthias Kaehlcke wrote:
> > Now that devfreq supports limiting the frequency range of a device
> > through PM QoS make use of it instead of disabling OPPs that should
> > not be used.
> > 
> > The switch from disabling OPPs to PM QoS introduces a subtle behavioral
> > change in case of conflicting requests (min > max): PM QoS gives
> > precedence to the MIN_FREQUENCY request, while higher OPPs disabled
> > with dev_pm_opp_disable() would override MIN_FREQUENCY.
> > 
> > Signed-off-by: Matthias Kaehlcke <mka@xxxxxxxxxxxx>
> > ---
> > 
> > Changes in v2:
> > - added documentation for 'req_max_freq'
> > - fixed jumps in of_devfreq_cooling_register_power() unwind
> > - added comment about behavioral change to the commit message
> > 
> >  drivers/thermal/devfreq_cooling.c | 70 ++++++++++---------------------
> >  1 file changed, 23 insertions(+), 47 deletions(-)
> > 
> > diff --git a/drivers/thermal/devfreq_cooling.c b/drivers/thermal/devfreq_cooling.c
> > index ef59256887ff63..cbbaf5bc425d1a 100644
> > --- a/drivers/thermal/devfreq_cooling.c
> > +++ b/drivers/thermal/devfreq_cooling.c
> > @@ -24,11 +24,13 @@
> >  #include <linux/idr.h>
> >  #include <linux/slab.h>
> >  #include <linux/pm_opp.h>
> > +#include <linux/pm_qos.h>
> >  #include <linux/thermal.h>
> >  
> >  #include <trace/events/thermal.h>
> >  
> > -#define SCALE_ERROR_MITIGATION 100
> > +#define HZ_PER_KHZ		1000
> > +#define SCALE_ERROR_MITIGATION	100
> >  
> >  static DEFINE_IDA(devfreq_ida);
> >  
> > @@ -53,6 +55,8 @@ static DEFINE_IDA(devfreq_ida);
> >   *		'utilization' (which is	'busy_time / 'total_time').
> >   *		The 'res_util' range is from 100 to (power_table[state] * 100)
> >   *		for the corresponding 'state'.
> > + * @req_max_freq:	PM QoS request for limiting the maximum frequency
> > + *			of the devfreq device.
> >   */
> >  struct devfreq_cooling_device {
> >  	int id;
> > @@ -65,49 +69,9 @@ struct devfreq_cooling_device {
> >  	struct devfreq_cooling_power *power_ops;
> >  	u32 res_util;
> >  	int capped_state;
> > +	struct dev_pm_qos_request req_max_freq;
> >  };
> >  
> > -/**
> > - * partition_enable_opps() - disable all opps above a given state
> > - * @dfc:	Pointer to devfreq we are operating on
> > - * @cdev_state:	cooling device state we're setting
> > - *
> > - * Go through the OPPs of the device, enabling all OPPs until
> > - * @cdev_state and disabling those frequencies above it.
> > - */
> > -static int partition_enable_opps(struct devfreq_cooling_device *dfc,
> > -				 unsigned long cdev_state)
> > -{
> > -	int i;
> > -	struct device *dev = dfc->devfreq->dev.parent;
> > -
> > -	for (i = 0; i < dfc->freq_table_size; i++) {
> > -		struct dev_pm_opp *opp;
> > -		int ret = 0;
> > -		unsigned int freq = dfc->freq_table[i];
> > -		bool want_enable = i >= cdev_state ? true : false;
> > -
> > -		opp = dev_pm_opp_find_freq_exact(dev, freq, !want_enable);
> > -
> > -		if (PTR_ERR(opp) == -ERANGE)
> > -			continue;
> > -		else if (IS_ERR(opp))
> > -			return PTR_ERR(opp);
> > -
> > -		dev_pm_opp_put(opp);
> > -
> > -		if (want_enable)
> > -			ret = dev_pm_opp_enable(dev, freq);
> > -		else
> > -			ret = dev_pm_opp_disable(dev, freq);
> > -
> > -		if (ret)
> > -			return ret;
> > -	}
> > -
> > -	return 0;
> > -}
> > -
> >  static int devfreq_cooling_get_max_state(struct thermal_cooling_device *cdev,
> >  					 unsigned long *state)
> >  {
> > @@ -134,7 +98,7 @@ static int devfreq_cooling_set_cur_state(struct thermal_cooling_device *cdev,
> >  	struct devfreq_cooling_device *dfc = cdev->devdata;
> >  	struct devfreq *df = dfc->devfreq;
> >  	struct device *dev = df->dev.parent;
> > -	int ret;
> > +	unsigned long freq;
> >  
> >  	if (state == dfc->cooling_state)
> >  		return 0;
> > @@ -144,9 +108,10 @@ static int devfreq_cooling_set_cur_state(struct thermal_cooling_device *cdev,
> >  	if (state >= dfc->freq_table_size)
> >  		return -EINVAL;
> >  
> > -	ret = partition_enable_opps(dfc, state);
> > -	if (ret)
> > -		return ret;
> > +	freq = dfc->freq_table[state];
> > +
> > +	dev_pm_qos_update_request(&dfc->req_max_freq,
> > +				  DIV_ROUND_UP(freq, HZ_PER_KHZ));
> >  
> >  	dfc->cooling_state = state;
> >  
> > @@ -529,9 +494,15 @@ of_devfreq_cooling_register_power(struct device_node *np, struct devfreq *df,
> >  	if (err)
> >  		goto free_dfc;
> >  
> > -	err = ida_simple_get(&devfreq_ida, 0, 0, GFP_KERNEL);
> > +	err = dev_pm_qos_add_request(df->dev.parent, &dfc->req_max_freq,
> > +				     DEV_PM_QOS_MAX_FREQUENCY,
> > +				     PM_QOS_MAX_FREQUENCY_DEFAULT_VALUE);
> >  	if (err < 0)
> >  		goto free_tables;
> > +
> > +	err = ida_simple_get(&devfreq_ida, 0, 0, GFP_KERNEL);
> > +	if (err < 0)
> > +		goto remove_qos_req;
> >  	dfc->id = err;
> >  
> >  	snprintf(dev_name, sizeof(dev_name), "thermal-devfreq-%d", dfc->id);
> > @@ -552,6 +523,10 @@ of_devfreq_cooling_register_power(struct device_node *np, struct devfreq *df,
> >  
> >  release_ida:
> >  	ida_simple_remove(&devfreq_ida, dfc->id);
> > +
> > +remove_qos_req:
> > +	dev_pm_qos_remove_request(&dfc->req_max_freq);
> > +
> >  free_tables:
> >  	kfree(dfc->power_table);
> >  	kfree(dfc->freq_table);
> > @@ -600,6 +575,7 @@ void devfreq_cooling_unregister(struct thermal_cooling_device *cdev)
> >  
> >  	thermal_cooling_device_unregister(dfc->cdev);
> >  	ida_simple_remove(&devfreq_ida, dfc->id);
> > +	dev_pm_qos_remove_request(&dfc->req_max_freq);
> >  	kfree(dfc->power_table);
> >  	kfree(dfc->freq_table);
> >  
> > 
> 
> Reviewed-by: Chanwoo Choi <cw00.choi@xxxxxxxxxxx>
> 
> -- 
> Best Regards,
> Chanwoo Choi
> Samsung Electronics