linux-kernel - RE: [PATCH V3 8/9] thermal: da9062/61: Thermal junction temperature monitoring driver

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Date:   Wed, 9 Nov 2016 18:20:58 +0000
From:   Steve Twiss <stwiss.opensource@...semi.com>
To:     Lukasz Luba <lukasz.luba@....com>,
        Eduardo Valentin <edubezval@...il.com>,
        LINUX-KERNEL <linux-kernel@...r.kernel.org>,
        LINUX-PM <linux-pm@...r.kernel.org>,
        Zhang Rui <rui.zhang@...el.com>
CC:     DEVICETREE <devicetree@...r.kernel.org>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Guenter Roeck <linux@...ck-us.net>,
        LINUX-INPUT <linux-input@...r.kernel.org>,
        LINUX-WATCHDOG <linux-watchdog@...r.kernel.org>,
        Lee Jones <lee.jones@...aro.org>,
        "Liam Girdwood" <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Rob Herring <robh+dt@...nel.org>,
        Support Opensource <Support.Opensource@...semi.com>,
        Wim Van Sebroeck <wim@...ana.be>
Subject: RE: [PATCH V3 8/9] thermal: da9062/61: Thermal junction temperature
 monitoring driver

On 02 November 2016 13:29, Lukasz Luba wrote:
[...]

> Apart from these 2 comments, 10sec is not to long
> (waiting for the temperature change)?

Hi Lukasz,

Are you saying the maximum polling time is too long or too short if it
is fixed in the driver at 10 seconds?

Certainly 10 seconds can be seen as either too long or too short a time
when waiting for the temperature to fall-back below a threshold.
But, this maximum polling time will be application dependent I think.

However, this is a repeated polling event notifying of a warning
over-temperature condition, so, it is already known that the
temperature is above the threshold and action should already be
in progress to reduce the temperature.

#define DA9062_DEFAULT_POLLING_MS_PERIOD	3000
#define DA9062_MAX_POLLING_MS_PERIOD		10000
#define DA9062_MIN_POLLING_MS_PERIOD		1000

The TEMP_WARN first level temperature supervision is intended for
non-invasive temperature controlling measures for cooling the system
and are left to the host software. This first level temperature
TEMP_WARN (125 degC) is only +15degC off the next TEMP_CRIT
(140 degC) temperature threshold. And this TEMP_CRIT is where
the hardware will automatically shutdown.

I suppose it all depends on how fast the temperature is expected to
rise and fall.

In any case, this 10 second polling maximum value was provided as part
of guidance from a specific solution with this hardware. It would be expected
that any final implementation will also include a notify() function and any
of these settings could be altered to match the application where
appropriate.

I've added a comment above these defined variables for the next code
patch.

> On 31/10/16 16:02, Steve Twiss wrote:
> > From: Steve Twiss <stwiss.opensource@...semi.com>
> >
> > +static int da9062_thermal_probe(struct platform_device *pdev)
> > +{
> > +	struct da9062 *chip = dev_get_drvdata(pdev->dev.parent);
> > +	struct da9062_thermal *thermal;
> > +	unsigned int pp_tmp = DA9062_DEFAULT_POLLING_MS_PERIOD;
> > +	const struct of_device_id *match;
> > +	int ret = 0;
> > +
> > +	match = of_match_node(da9062_compatible_reg_id_table,
> > +			      pdev->dev.of_node);
> > +	if (!match)
> > +		return -ENXIO;
> > +
> > +	if (pdev->dev.of_node) {
> > +		if (!of_property_read_u32(pdev->dev.of_node,
> > +					"dlg,tjunc-temp-polling-period-ms",
> > +					&pp_tmp)) {
> > +			if (pp_tmp < DA9062_MIN_POLLING_MS_PERIOD ||
> > +				pp_tmp > DA9062_MAX_POLLING_MS_PERIOD)
> > +				pp_tmp = DA9062_DEFAULT_POLLING_MS_PERIOD;
>
> Maybe it's worth to add some print here just to mention about
> the DT value out of range. When you saw a dmesg with
> this print on some bug report, you would know about wrong DT entry
> (even if debug was not set).

I can add a dev_warn() here explaining the invalid configuration.

[...]

> > +static int da9062_thermal_remove(struct platform_device *pdev)
> > +{
> > +	struct	da9062_thermal *thermal = platform_get_drvdata(pdev);
> > +
> > +	free_irq(thermal->irq, thermal);
> > +	thermal_zone_device_unregister(thermal->zone);
> > +	cancel_delayed_work_sync(&thermal->work);
>
> You should change the order for these two functions
> and cancel the work before unregistering thermal zone device.

ok

Regards,
Steve