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From:   Stefan Schaeckeler <schaecsn@gmx.net>
To:     amit.kucheria@verdurent.com
CC:     heiko@sntech.de, linux-pm@vger.kernel.org,
        daniel.lezcano@linaro.org, linux-kernel@vger.kernel.org,
        edubezval@gmail.com, linux-rockchip@lists.infradead.org,
        rui.zhang@intel.com, linux-arm-kernel@lists.infradead.org
In-reply-to: <CAHLCerOHjAEEA1BpUqPdZvFwHMy11SqC+ZtjdFyManu7iOpBXA@mail.gmail.com>
        (message from Amit Kucheria on Thu, 12 Dec 2019 13:58:52 +0530)
Subject: Re: [RESEND PATCH] thermal: rockchip: enable hwmon
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References: <20191212061702.BFE2D6E85603@corona.crabdance.com> <CAHLCerOHjAEEA1BpUqPdZvFwHMy11SqC+ZtjdFyManu7iOpBXA@mail.gmail.com>
Message-Id: <20191212232859.E09FC6E85603@corona.crabdance.com>
Date:   Thu, 12 Dec 2019 15:28:59 -0800 (PST)
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Hello Amit,

> On Thu, Dec 12, 2019 at 11:47 AM Stefan Schaeckeler <schaecsn@gmx.net> w=
rote:
> >
> > 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 expos=
e
sensors.

Sensors exposed by hwmon are automagically found by userland clients. User=
s
want to run sensors(1) and expect them to show up.


Why in rockchip_thermal.c:

drivers/thermal/ provides a high-level hwmon api in thermal_hwmon.[hc] whi=
ch 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 hwm=
on
elsewhere. Most seem to do this in hwmon/, e.g. hwmon/coretemp.c. These dr=
ivers
are written from scratch. Utilizing thermal_hwmon.[ch] for chips which hav=
e
already drivers in drivers/thermal/ seems to be more elegant.

 Stefan