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

[Matthias Kaehlcke <mka@chromium.org>]

Hi Lukasz,

thanks for the review!

I'll rebase and send v3. Hopefully it doesn't cause too much extra
work for your changes.

Thanks

Matthias

On Thu, Mar 12, 2020 at 11:39:56AM +0000, Lukasz Luba wrote:
> Hi Matthias,
> 
> I just saw this email below the patch. I wasn't aware that you
> are working on this. I will have to update my changes...
> 
> It looks good to me.
> Unfortunately, it does not apply on top of Amit's commit
> 1b5cb9570670a6277cc0 thermal: devfreq_cooling: Appease the kernel-doc deity
> 
> Could you check this?
> 
> Other then that
> 
> Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
> 
> Regards,
> Lukasz
> 
> On 3/12/20 12:35 AM, Matthias Kaehlcke wrote:
> > 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@chromium.org>
> > > > ---
> > > > 
> > > > 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@samsung.com>
> > > 
> > > -- 
> > > Best Regards,
> > > Chanwoo Choi
> > > Samsung Electronics