linux-kernel - Re: [PATCH v2 2/8] power: supply: core: Add state_of

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Message-ID: <3ldf7w5cpv4wt63kvewl2a32abx4uohvir7zgefpqly5rytkcn@p5fslnvpnjn3>
Date: Thu, 5 Jun 2025 09:34:14 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@...ndries.io>
To: Fenglin Wu <fenglin.wu@....qualcomm.com>
Cc: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.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 2/8] power: supply: core: Add state_of_health power
 supply property

On Thu, Jun 05, 2025 at 02:08:30PM +0800, Fenglin Wu wrote:
> 
> On 6/3/2025 6:35 PM, Dmitry Baryshkov wrote:
> > > > > +What:		/sys/class/power_supply/<supply_name>/state_of_health
> > > > > +Date:		May 2025
> > > > > +Contact:	linux-arm-msm@...r.kernel.org
> > > > > +Description:
> > > > > +		Reports battery power supply state of health in percentage.
> > > > > +
> > > > > +		Access: Read
> > > > > +
> > > > > +		Valid values: 0 - 100 (percent)
> > > > What does it mean that battery has 77% of health?
> > > I will update this to explain it better:
> > > 
> > > Reports battery power supply state of health in percentage, indicating that the maximum charge capacity has degraded to that percentage of its original designed capacity.
> > Which basically means that we don't need it in the first place, as we
> > can read capacity_full and capacity_full_design (or energy_full /
> > energy_full_design) and divide one onto another.
> 
> Hmm, it is true in general to quantify how the battery performance has
> degraded over time. However, estimating and calculating for battery state of
> health is much more complicated I think. I am not an expert, but as far as I
> know, different battery management systems might have different algorithms
> to calculate the battery health and report it in as percentage. For example,
> in Qcom battery management firmware, a "soh" parameter is provided as the
> battery health percentage based on the real-time calculations from learning
> capacity, resistance estimation, etc.

Ack, this is more than just full / full_design. Please consider
expanding ABI description (though in the vendor-neutral way).

-- 
With best wishes
Dmitry