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From: Brian Norris <briannorris@chromium.org>
To: Rob Herring <robh@kernel.org>
Cc: Matthias Kaehlcke <mka@chromium.org>,
	MyungJoo Ham <myungjoo.ham@samsung.com>,
	Kyungmin Park <kyungmin.park@samsung.com>,
	Chanwoo Choi <cw00.choi@samsung.com>,
	Arnd Bergmann <arnd@arndb.de>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Mark Rutland <mark.rutland@arm.com>,
	linux-pm@vger.kernel.org, devicetree@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	Douglas Anderson <dianders@chromium.org>,
	Enric Balletbo i Serra <enric.balletbo@collabora.com>
Subject: Re: [PATCH v2 10/11] dt-bindings: misc: add bindings for cros_ec_throttler
Date: Tue, 12 Jun 2018 13:40:22 -0700	[thread overview]
Message-ID: <20180612204018.GB99983@rodete-desktop-imager.corp.google.com> (raw)
In-Reply-To: <20180612191011.GA26266@rob-hp-laptop>

Hi Rob,

On Tue, Jun 12, 2018 at 01:10:11PM -0600, Rob Herring wrote:
> On Thu, Jun 07, 2018 at 11:12:13AM -0700, Matthias Kaehlcke wrote:
> > The cros_ec_throttler monitors events from the Chrome OS Embedded
> > Controller to throttle the system if needed, using the mechanisms
> > provided by the throttler core.
> > 
> > Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
> > ---
> > Changes in v2:
> > - patch added to series
> > 
> >  Documentation/devicetree/bindings/misc/cros_ec_throttler.txt | 4 ++++
> >  1 file changed, 4 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/misc/cros_ec_throttler.txt
> > 
> > diff --git a/Documentation/devicetree/bindings/misc/cros_ec_throttler.txt b/Documentation/devicetree/bindings/misc/cros_ec_throttler.txt
> > new file mode 100644
> > index 000000000000..7316dcc0ef75
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/misc/cros_ec_throttler.txt
> > @@ -0,0 +1,4 @@
> > +* cros_ec_throttler driver
> 
> Bindings are for h/w, not drivers.

(OK, sure, don't call this "driver". And maybe this could use some more
description about what kind of events are emitted by this sort of
device.)

> I continue to fail to see why this needs to be in DT. There are other 
> ways to instantiate drivers.

This is mostly relevant to:
[PATCH v2 08/11] dt-bindings: PM / OPP: add opp-throttlers property

so it's probably good to take a look at that one too.

The primary purpose is to have a target to point at when determining who
is the source of throttling. This is similar to other CrOS EC subdevices
(e.g., PWM) where we technically don't require a subnode (the EC
firmware can its own PWM hardware without DT), but it is important that,
e.g., a backlight device has something to point at when it's using a PWM
attached to the EC. So we have a PWM subnode.

In this case, we're a little vague about what exactly the hardware is
here, but there *is* hardware that's emitting "throttle" events (hint:
here, it's related to sensing too high of system current). This is all
abstracted by firmware, which simply tells us we need to scale back our
power usage.

So, what do you think of patch 8? Should OPPs have phandles to such a
throttler? If so, should the phandle just point at the main EC device
(see mfd/cros-ec.txt), or is it reasonable to have a subnode to
represent something more specific?

Or maybe this is entirely on the wrong track. But this is the resulting
proposal after your comments on v1, so it's probably best we have a
clearer overall review of what makes sense here, so we don't just go in
cycles on new proposals that get rejected.

Brian

> > +
> > +Required properties:
> > +- compatible: "google,cros-ec-throttler"
> > -- 
> > 2.18.0.rc1.242.g61856ae69a-goog
> > 

  reply	other threads:[~2018-06-12 20:40 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-06-07 18:12 [PATCH v2 00/11] Add throttler driver for non-thermal throttling Matthias Kaehlcke
2018-06-07 18:12 ` [PATCH v2 01/11] PM / devfreq: Init user limits from OPP limits, not viceversa Matthias Kaehlcke
2018-06-07 18:12 ` [PATCH v2 02/11] PM / devfreq: Fix handling of min/max_freq == 0 Matthias Kaehlcke
2018-06-07 18:12 ` [PATCH v2 03/11] PM / devfreq: Don't adjust to user limits in governors Matthias Kaehlcke
2018-06-07 18:12 ` [PATCH v2 04/11] PM / devfreq: Add struct devfreq_policy Matthias Kaehlcke
2018-06-07 18:12 ` [PATCH v2 05/11] PM / devfreg: Add support for policy notifiers Matthias Kaehlcke
2018-06-08 23:21   ` kbuild test robot
2018-06-09  1:16   ` kbuild test robot
2018-06-07 18:12 ` [PATCH v2 06/11] PM / devfreq: Make update_devfreq() public Matthias Kaehlcke
2018-06-07 18:12 ` [PATCH v2 07/11] PM / devfreq: export devfreq_class Matthias Kaehlcke
2018-06-07 18:12 ` [PATCH v2 08/11] dt-bindings: PM / OPP: add opp-throttlers property Matthias Kaehlcke
2018-06-07 18:12 ` [PATCH v2 09/11] misc: throttler: Add core support for non-thermal throttling Matthias Kaehlcke
2018-06-09  4:34   ` kbuild test robot
2018-06-12  1:49   ` Brian Norris
2018-06-12 17:11     ` Matthias Kaehlcke
2018-06-12 20:00       ` Brian Norris
2018-06-13  1:48         ` Matthias Kaehlcke
2018-06-07 18:12 ` [PATCH v2 10/11] dt-bindings: misc: add bindings for cros_ec_throttler Matthias Kaehlcke
2018-06-12 19:10   ` Rob Herring
2018-06-12 20:40     ` Brian Norris [this message]
2018-06-13  2:00       ` Matthias Kaehlcke
2018-06-07 18:12 ` [PATCH v2 11/11] misc: throttler: Add Chrome OS EC throttler Matthias Kaehlcke
2018-06-08 14:09   ` Enric Balletbo i Serra
2018-06-08 15:56     ` Matthias Kaehlcke
2018-06-28 18:52 ` [PATCH v2 00/11] Add throttler driver for non-thermal throttling Pavel Machek

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