Message-ID: <f461ca33-0892-4a58-a40b-6da2a32d1430@oss.qualcomm.com>
Date: Fri, 30 Jan 2026 10:13:06 +0100
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Gaurav Kohli <gaurav.kohli@....qualcomm.com>,
        Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
Cc: Bjorn Andersson <andersson@...nel.org>, mathieu.poirier@...aro.org,
        robh@...nel.org, krzk+dt@...nel.org, conor+dt@...nel.org,
        rafael@...nel.org, daniel.lezcano@...aro.org, rui.zhang@...el.com,
        lukasz.luba@....com, konradybcio@...nel.org, amitk@...nel.org,
        mani@...nel.org, casey.connolly@...aro.org,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org
Subject: Re: [PATCH v1 2/8] remoteproc: qcom: probe all child devices

On 1/30/26 8:03 AM, Gaurav Kohli wrote:
> 
> On 1/28/2026 3:15 PM, Konrad Dybcio wrote:
>> On 1/28/26 10:39 AM, Gaurav Kohli wrote:
>>> On 1/27/2026 10:11 PM, Dmitry Baryshkov wrote:
>>>> On Tue, Jan 27, 2026 at 09:42:10PM +0530, Gaurav Kohli wrote:
>>>>> On 1/24/2026 12:33 AM, Dmitry Baryshkov wrote:
>>>>>> On Fri, Jan 23, 2026 at 07:23:39PM +0530, Gaurav Kohli wrote:
>>>>>>> On 1/8/2026 12:37 PM, Gaurav Kohli wrote:
>>>>>>>> On 1/3/2026 8:26 PM, Bjorn Andersson wrote:
>>>>>>>>> On Tue, Dec 23, 2025 at 06:02:21PM +0530, Gaurav Kohli wrote:
>>>>>>>>>> From: Casey Connolly <casey.connolly@...aro.org>
>>>>>>>>>>
>>>>>>>>>> Generalise the qcom,bam-dmux child node support by probing all
>>>>>>>>>> remoteproc children with of_platform_populate(). This will be used to
>>>>>>>>>> enable support for devices which are best represented as
>>>>>>>>>> subnodes of the
>>>>>>>>>> remoteproc, such as those representing QMI clients.
>>>>>>>>> Please flip this around, start with the description of the problem
>>>>>>>>> you're trying to solve.
>>>>>>>>>
>>>>>>>>>> Signed-off-by: Casey Connolly <casey.connolly@...aro.org>
>>>>>>>>> This must have your signed-off-by, where you certifies the origin of
>>>>>>>>> this patch.
>>>>>>>>>
>>>>>>>>>> ---
>>>>>>>>>>      drivers/remoteproc/qcom_q6v5.c     | 4 ++++
>>>>>>>>>>      drivers/remoteproc/qcom_q6v5_mss.c | 8 --------
>>>>>>>>>>      2 files changed, 4 insertions(+), 8 deletions(-)
>>>>>>>>>>
>>>>>>>>>> diff --git a/drivers/remoteproc/qcom_q6v5.c
>>>>>>>>>> b/drivers/remoteproc/qcom_q6v5.c
>>>>>>>>>> index 58d5b85e58cd..a02839c7ed8c 100644
>>>>>>>>>> --- a/drivers/remoteproc/qcom_q6v5.c
>>>>>>>>>> +++ b/drivers/remoteproc/qcom_q6v5.c
>>>>>>>>>> @@ -6,6 +6,7 @@
>>>>>>>>>>       * Copyright (C) 2014 Sony Mobile Communications AB
>>>>>>>>>>       * Copyright (c) 2012-2013, The Linux Foundation. All rights
>>>>>>>>>> reserved.
>>>>>>>>>>       */
>>>>>>>>>> +#include <linux/of_platform.h>
>>>>>>>>>>      #include <linux/kernel.h>
>>>>>>>>>>      #include <linux/platform_device.h>
>>>>>>>>>>      #include <linux/interconnect.h>
>>>>>>>>>> @@ -351,6 +352,8 @@ int qcom_q6v5_init(struct qcom_q6v5 *q6v5,
>>>>>>>>>> struct platform_device *pdev,
>>>>>>>>>>              return dev_err_probe(&pdev->dev, PTR_ERR(q6v5->path),
>>>>>>>>>>                           "failed to acquire interconnect path\n");
>>>>>>>>>>      +    of_platform_populate(q6v5->dev->of_node, NULL, NULL, q6v5->dev);
>>>>>>>>> There are other child nodes here, in particular the GLINK and SMD edges.
>>>>>>>>> Do we really want platform_devices registered for them?
>>>>>>>>>
>>>>>>>>> Regards,
>>>>>>>>> Bjorn
>>>>>>>> thanks for pointing this, can you please suggest the right approach.
>>>>>>>>
>>>>>>>> This should not impact glink, as that is registering as rproc sub node,
>>>>>>>> And we need rproc cooling as child node
>>>>>>>>
>>>>>>>> of remote proc subsytem to create probe dependency only.
>>>>>>>>
>>>>>>>>
>>>>>>>> Can we do platform populate for specific child, would that be right
>>>>>>>> approach. or we should create rproc cooling as independent of parent ?
>>>>>>>>
>>>>>>> HI Bjorn,
>>>>>>>
>>>>>>> I’d like to highlight the impact and details of placement of remoteproc
>>>>>>> cooling dt node:
>>>>>>>
>>>>>>>
>>>>>>> ->As a child of the remote proc subsystem node:
>>>>>>>        In this configuration, the cooling device will only be probed once the
>>>>>>> corresponding remote proc subsystem itself is probed.
>>>>>>>
>>>>>>> ->Outside the remote proc subsystem, may be part of soc node:
>>>>>>>        In this setup, the cooling device will be probed independently. It will
>>>>>>> wait until the remoteproc subsystem is brought up
>>>>>>>        before completing cooling registration.
>>>>>>>        The drawback here is that if the parent remoteproc subsystem is
>>>>>>> disabled, the cooling device will still undergo an
>>>>>>>        unnecessary probe, even though it cannot be registered.
>>>>>> Bjorns question was different. It wasn't about pushing cooling device
>>>>>> outside of the remoteproc node. It is about not registering the devices.
>>>>>>
>>>>>> Can we follow the approach outlined by qcom_add_smd_subdev() /
>>>>>> qcom_add_glink_subdev()?
>>>>> Hi Dmitry,
>>>>>
>>>>> Thanks for the review. Since the remoteproc cooling is a QMI-based driver,
>>>>> it will receive the
>>>>> subsystem up notification directly. Therefore, there’s no need to make it a
>>>>> subdev node or
>>>>> tie it into the init/reset sequence of remoteproc subsytem.
>>>> But you've added a subnode for it (and we are discussing exactly
>>>> of_platform_populate()) call. So, you are tying it to the remoteproc
>>>> device lifecycle instead of the remoteproc subsys, which seems strange
>>>> to me. There is no cooling device if the DSP is not running.
>>>
>>> For the cooling feature, we don’t need to define it as a subnode. The cooling subsystem becomes relevant only
>>> after the remote subsystem is up, at which point it will receive add/delete notifications from the QMI server.
>>>
>>>
>>> If child nodes must be modeled as subnodes for rproc, we can move the CDSP TMD out of the remoteproc and add in soc.
>>> Is there currently a way for the remoteproc core layer to call of_platform_populate() without requiring a subnode?
>> I think the question is "why can't you register the remoteproc device
>> as a cooling_device, with perhaps #cooling-cells = <1>; instead of
>> any form of children?"
>>
>> Konrad
> 
> 
> thanks Konrad, for the review.
> 
> As each subsystem can expose multiple thermal mitigation devices via the remoteproc TMD service, so need to define child node.

I think you're stuck in an XY problem - you keep insisting that adding
a subnode is your end goal, while you really want to achieve being able
to register multiple cooling devices. Or at least that's how I read your
messages since you happen not to give any explanation as to why it's
actually necessary.

In my previous message, I forgot that cells for cooling devices actually
represent the minimum and maximum cooling state allowed. But since the
API is just part of the kernel, there's nothing preventing us from
evolving it.

Currently, we have:

Documentation/devicetree/bindings/thermal/thermal-cooling-devices.yaml

properties:
  "#cooling-cells":
    description:
      Must be 2, in order to specify minimum and maximum cooling state used in
      the cooling-maps reference. The first cell is the minimum cooling state
      and the second cell is the maximum cooling state requested.
    const: 2

But I think it would be perfectly fine to suggest a change such that
if cells > 2, the last two cells keep the current behavior and the former
ones let you index into a cooling device exposed through a single OF node

e.g.

rproc_xyz: remoteproc {
	compatible = "qcom,rproc-xyz";

	...

	#cooling-device-cells = <3>;
};

...

thermal-zones {
	super-rproc-therm-a {
		thermal-sensors = <&rproc_xyz RPROC_XYZ_COOLING_A
				   THERMAL_NO_LIMIT THERMAL_NO_LIMIT>;

		trips { ... } ;
	};

	super-rproc-therm-b {
		thermal-sensors = <&rproc_xyz RPROC_XYZ_COOLING_B
				   THERMAL_NO_LIMIT THERMAL_NO_LIMIT>;

		trips { ... } ;
	};
};

This would be resolved by allowing drivers to register an .of_xlate-type
function which would take the RPROC_XYZ_COOLING_n argument and e.g. use
it as an index into struct thermal_cooling_device cdev[]; within the
driver struct.

Konrad

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