linux-kernel - RE: [PATCH V7 6/7] thermal: da9062/61: Thermal junction temperature monitoring driver

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Date:   Mon, 3 Apr 2017 13:21:19 +0000
From:   Steve Twiss <stwiss.opensource@...semi.com>
To:     Eduardo Valentin <edubezval@...il.com>,
        Lee Jones <lee.jones@...aro.org>
CC:     LINUX-KERNEL <linux-kernel@...r.kernel.org>,
        LINUX-PM <linux-pm@...r.kernel.org>,
        Zhang Rui <rui.zhang@...el.com>,
        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>,
        Liam Girdwood <lgirdwood@...il.com>,
        "Lukasz Luba" <lukasz.luba@....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 V7 6/7] thermal: da9062/61: Thermal junction temperature
 monitoring driver

On 01 April 2017 @20:59, Eduardo Valentin wrote:

> Subject: Re: [PATCH V7 6/7] thermal: da9062/61: Thermal junction temperature monitoring driver
> 
> On Tue, Mar 28, 2017 at 03:43:33PM +0100, Steve Twiss wrote:
> > From: Steve Twiss <stwiss.opensource@...semi.com>
> >
> > Add junction temperature monitoring supervisor device driver, compatible
> > with the DA9062 and DA9061 PMICs. A MODULE_DEVICE_TABLE() macro is added.
> >
> > If the PMIC's internal junction temperature rises above T_WARN (125 degC)
> > an interrupt is issued. This T_WARN level is defined as the
> > THERMAL_TRIP_HOT trip-wire inside the device driver.
> >
> > The thermal triggering mechanism is interrupt based and happens when the
> > temperature rises above a given threshold level. The component cannot
> > return an exact temperature, it only has knowledge if the temperature is
> > above or below a given threshold value. A status bit must be polled to
> > detect when the temperature falls below that threshold level again. A
> > kernel work queue is configured to repeatedly poll and detect when the
> > temperature falls below this trip-wire, between 1 and 10 second intervals
> > (defaulting at 3 seconds).
> >
> > This scheme is provided as an example. 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.
> >
> > When over-temperature is reached, the interrupt from the DA9061/2 will be
> > repeatedly triggered. The IRQ is therefore disabled when the first
> > over-temperature event happens and the status bit is polled using a
> > work-queue until it becomes false.
> >
> > This strategy is designed to allow the periodic transmission of uevents
> > (HOT trip point) as the first level of temperature supervision method. It
> > is intended for non-invasive temperature control, where the necessary
> > measures for cooling the system down are left to the host software. Once
> > the temperature falls again, the IRQ is re-enabled so a new critical
> > over-temperature event can be detected.
> >
> > Reviewed-by: Lukasz Luba <lukasz.luba@....com>
> > Signed-off-by: Steve Twiss <stwiss.opensource@...semi.com>
> 
> I have had a look on the history of this driver on its previous
> versions, and I do not think I have any other point to request on it.

Thank you.

> Obviously, I still need to state that I do not like its oddness as it is
> not really benefiting much of the thermal control implemented on the
> thermal subsystem.

Agreed.
But, it should be useful in the case of an over-temperature in the system PMIC 
when the OS needs to be notified to bring core temperature under control.

> What is the plan for this series? Am I expected to get this driver
> through thermal tree ? Or is this series going into a one shot?
> 
> If option 1 is the expected, would the driver need to get its
> mfd parent merged first?

Other components such as the ONKEY and Watchdog have not required the MFD
to be merged first. I don't see any strong dependency for the MFD to exist with this
thermal component.

I'm not sure how much Lee is waiting for Acks to exist before proceeding with the MFD.
I have TO:'d Lee Jones, for this case.

Regards,
Steve