Re: [PATCH 0/4] thermal: Introduce Qualcomm Thermal Mitigation Device support

From: Manivannan Sadhasivam <mani@kernel.org>
To: Bjorn Andersson <quic_bjorande@quicinc.com>
Cc: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>,
	Caleb Connolly <caleb.connolly@linaro.org>,
	Andy Gross <agross@kernel.org>,
	Bhupesh Sharma <bhupesh.linux@gmail.com>,
	Bjorn Andersson <andersson@kernel.org>,
	Konrad Dybcio <konrad.dybcio@linaro.org>,
	Mathieu Poirier <mathieu.poirier@linaro.org>,
	Rob Herring <robh+dt@kernel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
	Conor Dooley <conor+dt@kernel.org>,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	Daniel Lezcano <daniel.lezcano@linaro.org>,
	Amit Kucheria <amitk@kernel.org>, Zhang Rui <rui.zhang@intel.com>,
	Sibi Sankar <quic_sibis@quicinc.com>,
	Thara Gopinath <thara.gopinath@gmail.com>,
	linux-arm-msm@vger.kernel.org, linux-remoteproc@vger.kernel.org,
	devicetree@vger.kernel.org, linux-pm@vger.kernel.org
Subject: Re: [PATCH 0/4] thermal: Introduce Qualcomm Thermal Mitigation Device support
Date: Tue, 10 Oct 2023 17:54:47 +0530	[thread overview]
Message-ID: <20231010122447.GJ4884@thinkpad> (raw)
In-Reply-To: <20231005023658.GE3553829@hu-bjorande-lv.qualcomm.com>

On Wed, Oct 04, 2023 at 07:36:58PM -0700, Bjorn Andersson wrote:
> On Mon, Oct 02, 2023 at 09:43:08PM +0530, Manivannan Sadhasivam wrote:
> > On Mon, Oct 02, 2023 at 07:00:27PM +0300, Dmitry Baryshkov wrote:
> > > On Mon, 2 Oct 2023 at 18:58, Manivannan Sadhasivam <mani@kernel.org> wrote:
> > > >
> > > > On Mon, Oct 02, 2023 at 06:00:37PM +0300, Dmitry Baryshkov wrote:
> > > > > On Mon, 2 Oct 2023 at 17:52, Manivannan Sadhasivam <mani@kernel.org> wrote:
> > > > > >
> > > > > > On Sun, Oct 01, 2023 at 06:26:14PM +0100, Caleb Connolly wrote:
> > > > > > >
> > > > > > >
> > > > > > > On 01/10/2023 16:57, Manivannan Sadhasivam wrote:
> > > > > > > > On Fri, Sep 29, 2023 at 05:16:16PM +0100, Caleb Connolly wrote:
> > > > > > > > > The Thermal Mitigation Device (TMD) Service is a QMI service that runs
> > > > > > > > > on remote subsystems (the modem and DSPs) on Qualcomm SoCs.
> > > > > > > > > It exposes various mitigations including passive thermal controls and
> > > > > > > > > rail voltage restrictions.
> > > > > > > > >
> > > > > > > > > This series introduces support for exposing TMDs as cooling devices
> > > > > > > > > in the kernel through the thermal framework, using the QMI interface.
> > > > > > > > >
> > > > > > > > > Each TMD client is described as a child of the remoteproc node in
> > > > > > > > > devicetree. With subnodes for each control.
> > > > > > > > >
> > > > > > > >
> > > > > > > > Daniel expressed concerns in the past aganist representing TMD driver as a
> > > > > > > > cooling device since it is not tied to thermal zones and the governors cannot
> > > > > > > > use it. Instead he suggested to represent it as a powercap device with thermal
> > > > > > > > constraints.
> > > > > > >
> > > > > > > Hi Mani,
> > > > > > >
> > > > > > > Forgive me as I'm not yet super familiar with the thermal subsystem.
> > > > > > >
> > > > > > > As I understand it, the DT layout here enables each control to be referenced
> > > > > > > under the thermal zones, at least this is the approach taken in CAF 4.9.
> > > > > > >
> > > > > > > Maybe I don't quite understand what you mean, are you saying that using
> > > > > > > thermal zones is the wrong approach?
> > > > > >
> > > > > > Thermal framework expects each thermal zone represented in DT to have atleast
> > > > > > one corresponding thermal sensor defined using "thermal-sensors" property. But
> > > > > > with TMD, there is no thermal sensor AFAIK.
> > > > >
> > > > > As far as I understand, no. It is perfectly fine to have 'cooling'
> > > > > devices, which react to external thermal monitoring events. I might be
> > > > > mistaken, but I think that is the case here, isn't it?
> > > > >
> > > >
> > > > Yes it is represented as cooling device(s). But I do not see any cognizant way
> > > > to plug it with thermal zones i.e., unless TMD itself reports temperature of the
> > > > modem, using it as a cooling device for external temperature events doesn't
> > > > sound good to me.
> > > 
> > > Why? We have compute, q6, wlan tsens sensors. So it seems natural to
> > > tell CDSP to slow down if compute sensor reports overheating.
> > > 
> > 
> > TMD is for external devices such as PCIe modems as well. Is there a temperature
> > sensor for that?
> > 
> 
> According to the schematics for the SC8280XP CRD sys_therm5 would be the
> sensor you're looking for.
> 

Hmm, then it seems fine from my end as long we have the correct sensor data to
hook up these cooling devices.

- Mani

> Regards,
> Bjorn

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