linux-kernel - Re: [PATCH 1/3] thermal: hisilicon: add new hisilicon thermal sensor driver

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Date:	Mon, 23 Mar 2015 12:46:12 +0800
From:	Leo Yan <leo.yan@...aro.org>
To:	Mark Rutland <mark.rutland@....com>
Cc:	kongxinwei <kong.kongxinwei@...ilicon.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"linuxarm@...wei.com" <linuxarm@...wei.com>,
	"xuwei5@...ilicon.com" <xuwei5@...ilicon.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"edubezval@...il.com" <edubezval@...il.com>,
	"rui.zhuang@...el.com" <rui.zhuang@...el.com>,
	"liguozhu@...ilicon.com" <liguozhu@...ilicon.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 1/3] thermal: hisilicon: add new hisilicon thermal sensor
 driver

On Fri, Mar 20, 2015 at 03:55:27PM +0000, Mark Rutland wrote:
> > > That may be the case in the code as it stands today, but per the binding
> > > the trip points are the temperatures at which an action is to be taken.
> > > 
> > > The thermal-zone has poilling-delay and polling-delay-passive, but
> > > there's no reason you couldn't also use the interrupt to handle the
> > > "hot" trip-point, adn the reset at the "critical" trip-point. All that's
> > > missing is the plumbing in order to do so.
> > > 
> > > So please co-ordinate with the thermal framework to do that.
> > 
> > Let's dig further more for this point, so that we can get more specific
> > gudiance and have a good preparation for next version's patch set.
> > 
> > After i reviewed the thermal framework code, currently have one smooth
> > way to co-ordinate the trip points w/t thermal framework: use the function
> > *thermal_zone_device_register()* to register sensor, and can use the
> > callback function .get_trip_temp to tell thermal framework for the
> > trip points' temperature.
> > 
> > For hisi thermal case, now the driver is using the function
> > *thermal_zone_of_sensor_register* to register sensor, but use this way
> > i have not found there have standard APIs which can be used by sensor
> > driver to get the trip points info from thermal framework.
> > 
> > I may miss something for thermal framework, so if have existed APIs to
> > get the trip points, could pls point out?
> 
> I am only familiar with the binding, not the Linux implementation -- The
> latter can change to accomodate your hardware without requiring binding
> changes. Please co-ordinate with the thermal maintainers.

Found the functions of_thermal_get_trip_points(tz) and of_thermal_get_ntrips(tz)
will help for this.

> > > > > > +       if (of_property_read_bool(np, "hisilicon,tsensor-bind-irq")) {
> > > > > > +
> > > > > > +               if (data->irq_bind_sensor != -1)
> > > > > > +                       dev_warn(&pdev->dev, "irq has bound to index %d\n",
> > > > > > +                                data->irq_bind_sensor);
> > > > > > +
> > > > > > +               /* bind irq to this sensor */
> > > > > > +               data->irq_bind_sensor = index;
> > > > > > +       }
> > > > > 
> > > > > I don't see why this should be specified in the DT. Why do you believe
> > > > > it should?
> > > > 
> > > > The thermal sensor module has four sensors, but have only one
> > > > interrupt signal; This interrupt can only be used by one sensor;
> > > > So want to use dts to bind the interrupt with one selected sensor.
> > > 
> > > That's not all that great, though I'm not exactly sure how the kernel
> > > would select the best sensor to measure with. It would be good if you
> > > could talk to the thermal maintainers w.r.t. this.
> > 
> > This will be decided by the silicon, right? Every soc has different
> > combination with cpu/gpu/vpu, so which part is hottest, this maybe
> > highly dependent on individual SoC.
> > 
> > S/W just need provide the flexibility so that later can choose
> > the interrupt to bind with the sensor within the hottest part.
> 
> Then the property you care about is which sensor is closest to what is
> likely to be the hottest component. Given that, the kernel can decide
> how to use the interrupt.

Will modify the driver to dynamically bind the interrupt to hottest
sensor; Appreciate for good suggestion.

Thanks,
Leo Yan
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