linux-kernel - Re: [PATCH v2 5/8] power: supply: qcom_battmgr: Add charge control support

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Message-ID: <b938b358-301a-4842-bdf6-93ec3c459d41@oss.qualcomm.com>
Date: Mon, 9 Jun 2025 10:17:00 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Fenglin Wu <fenglin.wu@....qualcomm.com>,
        Konrad Dybcio <konrad.dybcio@....qualcomm.com>
Cc: György Kurucz <me@...uczgy.com>,
        Sebastian Reichel <sre@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>, Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley
 <conor+dt@...nel.org>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Subbaraman Narayanamurthy <subbaraman.narayanamurthy@....qualcomm.com>,
        David Collins <david.collins@....qualcomm.com>,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, kernel@....qualcomm.com,
        devicetree@...r.kernel.org, linux-usb@...r.kernel.org
Subject: Re: [PATCH v2 5/8] power: supply: qcom_battmgr: Add charge control
 support

On 09/06/2025 05:39, Fenglin Wu wrote:
> 
> On 6/7/2025 5:46 PM, Konrad Dybcio wrote:
>> On 6/3/25 12:37 PM, Dmitry Baryshkov wrote:
>>> On Tue, Jun 03, 2025 at 01:48:11PM +0800, Fenglin Wu wrote:
>>>> On 5/31/2025 6:36 PM, György Kurucz wrote:
>>>>>> Add charge control support for SM8550 and X1E80100.
>>>>> Thank you for this, tested on my Lenovo Yoga Slim 7x, the limiting 
>>>>> works
>>>>> well, I finally don't have to worry about leaving my laptop plugged in
>>>>> for too long.
>>>>>
>>>>> One small thing I noticed is that after setting the sysfs values and
>>>>> rebooting, they report 0 again. The limiting appears to stay in effect
>>>>> though, so it seems that the firmware does keep the values, but Linux
>>>>> does not read them back. Indeed, looking at the code, it seems that
>>>>> actually reading back the values is only implemented for the SM8550.
>>>> Right.
>>>>
>>>> Based on offline information, X1E80100 doesn't support reading back 
>>>> those
>>>> threshold values in battery management firmware, so I can only use the
>>>> cached values for sysfs read.
>>> Which limits usablity of the attribute, it is now impossible to identify
>>> whether it is enabled or disabled. Is there a chance of fixing that for
>>> the X1E80100 platform?
>> Is there a chance we store that value in SDAM and can read it back?
>>
>> Konrad
> 
> The thresholds are stored in PMIC SDAM registers by ADSP after receiving 
> the set requests, and ADSP reads them back during initialization. This 
> is why ADSP retains them upon device reboot.
> 
> I spoke with the battery management firmware team, and they have no 
> plans to update the battery management firmware for X1E80100 further. 
> Consequently, they cannot provide any interfaces to read these 
> thresholds through PMIC Glink.
> 
> Reading them from the existing SDAM registers requires adding "nvmem- 
> cells" DT properties to specify the SDAM registers. However, the 
> "pmic_glink.power-supply" device is an auxiliary device created by the 
> pmic_glink driver and does not have an associated DT node. Is there any 
> method to create a DT node and add DT properties for an auxiliary device?

Auxiliary-bus devices don't have their OF nodes. Instead they use the 
main device's of node thanks to the call to device_set_of_node_from_dev().

-- 
With best wishes
Dmitry