linux-kernel - Re: [RESEND PATCH] thermal: rockchip: enable hwmon

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Date:   Fri, 13 Dec 2019 10:09:49 +0530
From:   Amit Kucheria <amit.kucheria@...durent.com>
To:     schaecsn@....net, jdelvare@...e.com, linux@...ck-us.net
Cc:     Heiko Stuebner <heiko@...ech.de>,
        Linux PM list <linux-pm@...r.kernel.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Eduardo Valentin <edubezval@...il.com>,
        linux-rockchip@...ts.infradead.org,
        Zhang Rui <rui.zhang@...el.com>,
        lakml <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [RESEND PATCH] thermal: rockchip: enable hwmon

Fix Guenter's email.

On Fri, Dec 13, 2019 at 10:08 AM Amit Kucheria
<amit.kucheria@...durent.com> wrote:
>
> Hi Stefan,
>
> On Fri, Dec 13, 2019 at 4:59 AM Stefan Schaeckeler <schaecsn@....net> wrote:
> >
> > Hello Amit,
> >
> > > On Thu, Dec 12, 2019 at 11:47 AM Stefan Schaeckeler <schaecsn@....net> wrote:
> > > >
> > > > By default, of-based thermal drivers do not enable hwmon.
> > > > Explicitly enable hwmon for both, the soc and gpu temperature
> > > > sensor.
> > >
> > > Is there any reason you need to expose this in hwmon?
> >
> > Why hwmon:
> >
> > The soc embedds temperature sensors and hwmon is the standard way to expose
> > sensors.
>
> Let me rephrase - is there something in the hwmon subsystem that is
> needed that isn't provided by the thermal subsystem inside
> /sys/class/thermal?
>
> > Sensors exposed by hwmon are automagically found by userland clients. Users
> > want to run sensors(1) and expect them to show up.
> >
>
> That is a good point. In which case, I wonder if we should just fix
> this in of-thermal.c instead of requiring individual drivers to do
> write boilerplate code. I'm thinking of a flag that the driver could
> set to enable the thermal_hwmon interface for of-thermal drivers.
>
> > Why in rockchip_thermal.c:
> >
> > drivers/thermal/ provides a high-level hwmon api in thermal_hwmon.[hc] which is
> > used by at least these thermal drivers: rcar_gen3_thermal.c, rcar_thermal.c,
> > st/stm_thermal.c, and broadcom/bcm2835_thermal.c. I want to hook up
> > rockchip_thermal.c exactly the same way.
> >
> > Apparently, other architectures hook up the cpu temperature sensors to hwmon
> > elsewhere. Most seem to do this in hwmon/, e.g. hwmon/coretemp.c. These drivers
> > are written from scratch. Utilizing thermal_hwmon.[ch] for chips which have
> > already drivers in drivers/thermal/ seems to be more elegant.
> >
> >  Stefan