Re: [PATCH 3/4] arm64: dts: qcom: Add Shikra CQM SoM platform

[Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>]

On 6/30/26 2:42 PM, Rakesh Kota wrote:
> On Sun, Jun 28, 2026 at 03:33:23PM +0300, Dmitry Baryshkov wrote:
>> On Thu, Jun 25, 2026 at 09:11:19PM +0530, Kamal Wadhwa wrote:
>>> On Wed, Jun 17, 2026 at 03:48:14PM +0300, Dmitry Baryshkov wrote:
>>>> On Mon, 18 May 2026 at 14:49, Kamal Wadhwa
>>>> <kamal.wadhwa@oss.qualcomm.com> wrote:
>>>>>
>>>>> On Sun, May 17, 2026 at 08:18:15PM +0300, Dmitry Baryshkov wrote:
>>>>>> On Thu, May 14, 2026 at 04:09:18PM +0530, Kamal Wadhwa wrote:
>>>>>>> On Wed, May 13, 2026 at 06:14:20PM +0300, Dmitry Baryshkov wrote:
>>>>>>>> On 13/05/2026 17:29, Rakesh Kota wrote:
>>>>>>>>> On Wed, May 13, 2026 at 03:01:47PM +0300, Dmitry Baryshkov wrote:
>>>>>>>>>> On Wed, May 13, 2026 at 04:28:35AM +0000, sashiko-bot@kernel.org wrote:
>>>>>>>>>>> Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:
>>>>>>>>>>> - [High] The PMIC regulator definitions omit their required input supply dependencies (e.g., `vdd_s2-supply`, `vdd_l3-supply`), breaking the power hierarchy.
>>>>>>>>>>> - [Medium] The device tree inaccurately hardcodes the `compatible` string to a different PMIC model (`qcom,rpm-pm2250-regulators`) instead of explicitly identifying the actual hardware (PM4125).
>>>>>>>>>>> --
>>>>>>>>>>>> +
>>>>>>>>>>>> +         pm4125_s2: s2 {
>>>>>>>>>>>> +                 regulator-min-microvolt = <1000000>;
>>>>>>>>>>>> +                 regulator-max-microvolt = <1200000>;
>>>>>>>>>>>> +         };
>>>>>>>>>>>
>>>>>>>>>>> Do these regulators need to explicitly define their input supply dependencies
>>>>>>>>>>> such as vdd_s2-supply?
>>>>>>>>>>>
>>>>>>>>>>> Without these properties, the regulator framework might be unaware that the
>>>>>>>>>>> PMIC regulators draw power from upstream supplies.
>>>>>>>>>>>
>>>>>>>>>>> If the kernel dynamically manages the upstream supply and its reference count
>>>>>>>>>>> drops to zero, could it be disabled, causing an unexpected power loss for
>>>>>>>>>>> downstream components?
>>>>>>>>>>
>>>>>>>>>> And this is a correct comment. Please provide missing supplies.
>>>>>>>>>>
>>>>>>>>> As per the Qualcomm system design, the parent-child supply relationship
>>>>>>>>> is managed by the RPM firmware, not the Linux regulator framework. The
>>>>>>>>> RPM ensures the parent supply is never disabled until all subsystem
>>>>>>>>> votes are cleared.
>>>>>>>>
>>>>>>>> How is this different from other, previous platforms?
>>>>>>>
>>>>>>> This is not different. In the previous platforms too this is taken care from the
>>>>>>> RPM/RPMH firmware side, the only case where we may need explicit vote to parent
>>>>>>> is for non-rpmh/rpm regulator rails (like i2c based regulator pm8008), which
>>>>>>> may have a RPM/RPMH regulator as a parent.
>>>>>>>
>>>>>>> Even on those previous targets the parent rail of all RPM/RPMH regulators are
>>>>>>> internally voted by RPM/RPMH FW at proper voltage with required headroom
>>>>>>> calculated based on the active child rails. This was done for all the
>>>>>>> subsystems (including APPS) regulators.
>>>>>>>
>>>>>>> So no explicit handling from the APPS is required for parent supply.
>>>>>>
>>>>>> You are explaining the driver behaviour. But the question is about the
>>>>>> hardware description. If there is no difference, please add necessary
>>>>>> supplies back.
>>>>>
>>>>> I understand your concern about descibing the parent-child relation in the
>>>>> devicetree, and given that we have been almost always followed this for all
>>>>> the previous targets, it will expected of us to add them.
>>>>
>>>> Yes.
>>>>
>>>>>
>>>>> However, we want to avoid the unnecessary access to the parent from APPS.
>>>>
>>>> Why? What is the reason? Do we want to do the same for all the
>>>> platforms? Only for Shikra? Something else?
>>>>
>>>>> At the moment, I do not see a way to avoid that, if we add the parent
>>>>> regulators.
>>>>
>>>> That depend on the answer to the previous question. In the end, we can
>>>> make the driver ignore the parents by removing them from the regulator
>>>> desc.
>>>
>>> Ok, this seems like a good suggestion, so you mean its ok if we define the
>>> regulator desc's supply column with NULL? And only keep that in the DT?
>>>
>>> you mean like this?
>>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/regulator/qcom-rpmh-regulator.c?h=v7.1#n1453
>>>
>>> (please let me know if i got that right. thanks)
>>
>> Yes. Don't forget to explain in the commit message, why you are doing
>> so.
> 
> Currently, Agatti uses the same PMIC, so we cannot set the driver
> supply name reference to NULL. Since it's an older target,
> we'll need to run a regression before making any driver-level changes.
> 
> Additionally, the child-to-parent regulator ganging differs between
> Shikra and Agatti:
> 
>  - On Agatti, l3 regulator is ganged with vdd_l13_l14_l15_l16
>  - On Shikra, l3 is ganged with vdd_l2_l3

Is it configurable on the PMIC level? I was under the impression the
supply maps are fixed in hardware.  Is there a chance the agatti
description is just wrong?

Konrad

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