linux-kernel - Re: [PATCH v3 2/3] dt-bindings: iio: adc: Add support for QCOM PMIC5 Gen3 ADC

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Date: Wed, 21 Feb 2024 11:06:07 +0530
From: Jishnu Prakash <quic_jprakash@...cinc.com>
To: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>, <jic23@...nel.org>,
        <robh+dt@...nel.org>, <krzysztof.kozlowski+dt@...aro.org>,
        <conor+dt@...nel.org>, <andersson@...nel.org>,
        <konrad.dybcio@...aro.org>, <lee@...nel.org>,
        <andriy.shevchenko@...ux.intel.com>, <daniel.lezcano@...aro.org>,
        <dmitry.baryshkov@...aro.org>
CC: <lars@...afoo.de>, <luca@...tu.xyz>, <marijn.suijten@...ainline.org>,
        <agross@...nel.org>, <sboyd@...nel.org>, <rafael@...nel.org>,
        <rui.zhang@...el.com>, <lukasz.luba@....com>,
        <linus.walleij@...aro.org>, <quic_subbaram@...cinc.com>,
        <quic_collinsd@...cinc.com>, <quic_amelende@...cinc.com>,
        <quic_kamalw@...cinc.com>, <kernel@...cinc.com>,
        <linux-kernel@...r.kernel.org>, <linux-arm-msm@...r.kernel.org>,
        <linux-arm-msm-owner@...r.kernel.org>, <linux-iio@...r.kernel.org>,
        <linux-pm@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <cros-qcom-dts-watchers@...omium.org>
Subject: Re: [PATCH v3 2/3] dt-bindings: iio: adc: Add support for QCOM PMIC5
 Gen3 ADC

Hi Krzysztof,

On 2/17/2024 7:43 PM, Krzysztof Kozlowski wrote:
> On 16/02/2024 11:39, Jishnu Prakash wrote:
>> Hi Krzysztof,
>>
>> On 1/4/2024 1:48 PM, Krzysztof Kozlowski wrote:
>>> On 31/12/2023 18:12, Jishnu Prakash wrote:
>>>> For the PMIC5-Gen3 type PMICs, ADC peripheral is present in HW for the
>>>> following PMICs: PMK8550, PM8550, PM8550B and PM8550VX PMICs.
>>>>
>>>> It is similar to PMIC5-Gen2, with SW communication to ADCs on all PMICs
>>>> going through PBS(Programmable Boot Sequence) firmware through a single
>>>> register interface. This interface is implemented on an SDAM (Shared
>>>> Direct Access Memory) peripheral on the master PMIC PMK8550 rather
>>>> than a dedicated ADC peripheral.
>>>>
>>>> Add documentation for PMIC5 Gen3 ADC and macro definitions for ADC
>>>> channels and virtual channels (combination of ADC channel number and
>>>> PMIC SID number) per PMIC, to be used by clients of this device.
>>>>
>>>> Changes since v2:
>>>> - Moved ADC5 Gen3 documentation into a separate new file.
>>> Changelog goes under ---.
>>>
>>> Why did you do this? What is the rationale? Sorry, this patchset goes
>>> nowhere.
>>
>>
>> I'll elaborate this more in the next patchset. There are two main
>> reasons for adding this documentation in a new file:
> 
> This was more than a month ago? You reply to my comment with 1.5 months
> delay?
> 
> Sorry, I am not in the context and I am not going back to it. I have
> many other emails where my questions are addressed faster than 1.5 months.
> 
> The patch is not even in my mailbox, long gone.
> Why you are making it so difficult for reviewers?
> 
> You will get answers like I am not in context, sorry. Next time don't
> respond after 1.5 months.
> 

You're right - I'll do my best to get back to review comments in a 
reasonable time frame.

> 
>>
>> 1.This device is not exactly like the existing QCOM VADC drivers as it
>> now combines VADC functionality (reading ADC channel on client request)
>> with ADC_TM functionality (thermal threshold monitoring).
> 
> Does no explain touching bindings. Your drivers don't matter for bindings.
> 
>>
>> 2.Adding this device's bindings in the existing qcom,spmi-vadc.yaml file
> 
> No rationale was provided in commit msg.
> 
>> is not possible as it would require updating some of the existing
>> top-level constraints. (for the older devices in that file, "reg" and
>> "interrupts" can have at most one item, while this device can have more
>> than one item under these properties.)
> 

> How is this a problem?

In qcom,spmi-vadc.yaml, we have the following top-level constraints for 
the "reg" and "interrupts" properties:

   reg:
     maxItems: 1

   interrupts:
     maxItems: 1

For the ADC5 Gen3 device being added now, these constraints cannot be 
followed always, as there may be more than one peripheral under one 
device instance, each with a corresponding interrupt. For example, the 
above properties could be like this for a ADC5 Gen3 device:

     reg = <0x9000>, <0x9100>;
     interrupts = <0x0 0x90 0x1 IRQ_TYPE_EDGE_RISING>,
                  <0x0 0x91 0x1 IRQ_TYPE_EDGE_RISING>;


I could not overwrite the top-level constraints for the new device 
"qcom,spmi-adc5-gen3" alone in qcom,spmi-vadc.yaml, so I tried to remove 
the constraints from the top level and add them back conditionally for 
all the device types separately, but you told me not to remove them 
(full message: 
https://lore.kernel.org/linux-iio/832053f4-bd5d-4e58-81bb-1a8188e7f364@linaro.org/)

Since these constraints cannot be modified for a specific new device or 
removed, I think the only way to accommodate this new device is to add 
it in its own new file.

Is this a sufficient justification for adding this documentation in a 
new file or do you have any other suggestions?

Thanks,
Jishnu

> 
> 
> Best regards,
> Krzysztof
>