From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751390AbeEaVKd (ORCPT ); Thu, 31 May 2018 17:10:33 -0400 Received: from mail-pg0-f65.google.com ([74.125.83.65]:40706 "EHLO mail-pg0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751135AbeEaVK1 (ORCPT ); Thu, 31 May 2018 17:10:27 -0400 X-Google-Smtp-Source: ADUXVKLymDfo1IAXKK+cE56wvkPYONGiA6y0+j83BNLOlPWQGXy7lvI1JpKv+kTwOa9aB4aAVY6oJg== Date: Thu, 31 May 2018 14:10:25 -0700 From: Matthias Kaehlcke To: Rob Herring Cc: MyungJoo Ham , Kyungmin Park , Chanwoo Choi , Arnd Bergmann , Greg Kroah-Hartman , Mark Rutland , linux-pm@vger.kernel.org, devicetree@vger.kernel.org, "linux-kernel@vger.kernel.org" , Brian Norris , Douglas Anderson Subject: Re: [PATCH 10/11] dt-bindings: misc: add bindings for throttler Message-ID: <20180531211025.GC88063@google.com> References: <20180525203043.249193-1-mka@chromium.org> <20180525203043.249193-11-mka@chromium.org> <20180531163159.GA4369@rob-hp-laptop> <20180531183404.GB88063@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.2 (2017-12-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, May 31, 2018 at 03:04:18PM -0500, Rob Herring wrote: > On Thu, May 31, 2018 at 1:34 PM, Matthias Kaehlcke wrote: > > Hi Rob, > > > > On Thu, May 31, 2018 at 11:31:59AM -0500, Rob Herring wrote: > >> On Fri, May 25, 2018 at 01:30:42PM -0700, Matthias Kaehlcke wrote: > >> > >> Commit msg? > > > > Will add some more info in the next revision. > > > >> > Signed-off-by: Matthias Kaehlcke > >> > --- > >> > .../devicetree/bindings/misc/throttler.txt | 41 +++++++++++++++++++ > >> > 1 file changed, 41 insertions(+) > >> > create mode 100644 Documentation/devicetree/bindings/misc/throttler.txt > >> > > >> > diff --git a/Documentation/devicetree/bindings/misc/throttler.txt b/Documentation/devicetree/bindings/misc/throttler.txt > >> > new file mode 100644 > >> > index 000000000000..92f13e94451a > >> > --- /dev/null > >> > +++ b/Documentation/devicetree/bindings/misc/throttler.txt > >> > @@ -0,0 +1,41 @@ > >> > +Throttler driver > >> > + > >> > +The Throttler is used for non-thermal throttling of system components like > >> > +CPUs or devfreq devices. > >> > >> This all looks very Linux specific and not a h/w device. Perhaps you can > >> add hint properties to OPP tables as to what entries can be used for > >> throttling, but otherwise this doesn't belong in DT. > > > > My idea is to allow multiple throttlers, which might operate on > > different throttling devices or use different OPPs for the same > > device. To support this a simple boolean hint that the OPP can be used > > for throttling would not be sufficient. > > > > What should work is a property with an array of phandles of the > > throttlers that use a given OPP. > > > > AFAIK it is currently not possible to enumerate the devfreq devices in > > the system, so besides the info in the OPPs the throttler itself would > > still need a phandle to the devfreq device(s) it uses. > > Why don't you fix that OS problem instead of working around it in DT? I can try, though it's not exclusively in my hands, depends on what the devfreq maintainers think about it. > > I envision something like this: > > > > gpu_opp_table: opp-table2 { > > compatible = "operating-points-v2"; > > > > opp00 { > > opp-hz = /bits/ 64 <200000000>; > > opp-microvolt = <800000>; > > }; > > opp01 { > > opp-hz = /bits/ 64 <297000000>; > > opp-microvolt = <800000>; > > opp-throttlers = <&cros_ec_throttler>; > > }; > > ... > > }; > > > > cros_ec_throttler: cros-ec-throttler { > > compatible = "google,cros-ec-throttler"; > > Is this an actual h/w device? The Chrome OS Embedded Controller is a MCU that communicates with Linux over SPI or I2C. The low-level communication with the EC is handled by drivers/mfd/cros_ec* and then there are multiple drivers representing 'remote devices' on top of this (rtc-cros-ec.c, extcon-usbc-cros-ec.c, pwm-cros-ec.c, ...). cros_ec_throttler is a similar 'device' that responds to signals from the EC with frequency adjustments.