From: Rudraksha Gupta <guptarud@gmail.com>

Add MAX17048 fuel gauge support.

Tested by comparing battery capacity readings between upstream (mainline
max17040 driver) and downstream (Samsung max17048_fuelgauge driver)
across a full discharge cycle. Upstream reads ~3% lower throughout. Both
track the discharge curve correctly:

  Upstream:   95 92 88 87 86 87 83 82 80 68 60 55 50 45 40 35 30 20 16 10 10 5 5 1
  Downstream: 95 94 92 91 91 89 87 86 84 73 64 59 51 48 43 38 33 23 17 14 12 8 6 3

Each pair of readings was collected by checking the upstream capacity
first, then moving the battery to a second expressatt running downstream
Android to check its capacity. The battery was then moved back to the
upstream device for the next reading. This swap occasionally caused the
upstream capacity to read slightly higher than the previous value
(e.g. 86 -> 87). When this happened, the reading was retaken after the
value settled.

Link: https://github.com/LineageOS/android_kernel_samsung_d2/blob/stable/cm-11.0-XNG3C/arch/arm/mach-msm/board-apexq-battery.c
Link: https://github.com/LineageOS/android_kernel_samsung_d2/blob/stable/cm-11.0-XNG3C/drivers/battery/Makefile#L5
Link: https://github.com/LineageOS/android_kernel_samsung_d2/blob/stable/cm-11.0-XNG3C/arch/arm/mach-msm/Makefile#L308

Assisted-by: Claude:claude-opus-4.6
Signed-off-by: Rudraksha Gupta <guptarud@gmail.com>
---
 .../dts/qcom/qcom-msm8960-samsung-expressatt.dts   | 24 ++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/arch/arm/boot/dts/qcom/qcom-msm8960-samsung-expressatt.dts b/arch/arm/boot/dts/qcom/qcom-msm8960-samsung-expressatt.dts
index ed913ca5b825..bc976008ae45 100644
--- a/arch/arm/boot/dts/qcom/qcom-msm8960-samsung-expressatt.dts
+++ b/arch/arm/boot/dts/qcom/qcom-msm8960-samsung-expressatt.dts
@@ -182,6 +182,23 @@ &gsbi5_serial {
 	status = "okay";
 };
 
+&gsbi5_i2c {
+	status = "okay";
+
+	fuel-gauge@36 {
+		compatible = "maxim,max17048";
+		reg = <0x36>;
+		maxim,double-soc;
+		maxim,rcomp = /bits/ 8 <0x62>;
+		maxim,alert-low-soc-level = <2>;
+		interrupt-parent = <&tlmm>;
+		interrupts = <67 IRQ_TYPE_EDGE_FALLING>;
+		pinctrl-0 = <&fuelgauge_alert_pin>;
+		pinctrl-names = "default";
+		wakeup-source;
+	};
+};
+
 &gsbi7 {
 	qcom,mode = <GSBI_PROT_I2C>;
 
@@ -582,6 +599,13 @@ touchkey_irq_pin: touchkey-irq-state {
 		bias-disable;
 	};
 
+	fuelgauge_alert_pin: fuelgauge-alert-state {
+		pins = "gpio67";
+		function = "gpio";
+		drive-strength = <2>;
+		bias-disable;
+	};
+
 	touchkey_i2c_pins: touchkey-i2c-state {
 		pins = "gpio71", "gpio72";
 		function = "gpio";

-- 
2.53.0

On Wed, Apr 01, 2026 at 01:28:50AM -0700, Rudraksha Gupta wrote:
> Add MAX17048 fuel gauge support.
> 
> Tested by comparing battery capacity readings between upstream (mainline
> max17040 driver) and downstream (Samsung max17048_fuelgauge driver)
> across a full discharge cycle. Upstream reads ~3% lower throughout. Both
> track the discharge curve correctly:
> 
>   Upstream:   95 92 88 87 86 87 83 82 80 68 60 55 50 45 40 35 30 20 16 10 10 5 5 1
>   Downstream: 95 94 92 91 91 89 87 86 84 73 64 59 51 48 43 38 33 23 17 14 12 8 6 3
> 
> Each pair of readings was collected by checking the upstream capacity
> first, then moving the battery to a second expressatt running downstream
> Android to check its capacity. The battery was then moved back to the
> upstream device for the next reading. This swap occasionally caused the
> upstream capacity to read slightly higher than the previous value
> (e.g. 86 -> 87). When this happened, the reading was retaken after the
> value settled.
> 
> Link: https://github.com/LineageOS/android_kernel_samsung_d2/blob/stable/cm-11.0-XNG3C/arch/arm/mach-msm/board-apexq-battery.c
> Link: https://github.com/LineageOS/android_kernel_samsung_d2/blob/stable/cm-11.0-XNG3C/drivers/battery/Makefile#L5
> Link: https://github.com/LineageOS/android_kernel_samsung_d2/blob/stable/cm-11.0-XNG3C/arch/arm/mach-msm/Makefile#L308
> 
> Assisted-by: Claude:claude-opus-4.6
> Signed-off-by: Rudraksha Gupta <guptarud@gmail.com>
> ---
>  .../dts/qcom/qcom-msm8960-samsung-expressatt.dts   | 24 ++++++++++++++++++++++
>  1 file changed, 24 insertions(+)
> 
Nice!


Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>



-- 
With best wishes
Dmitry

On 4/1/26 10:28 AM, Rudraksha Gupta via B4 Relay wrote:
> From: Rudraksha Gupta <guptarud@gmail.com>
> 
> Add MAX17048 fuel gauge support.
> 
> Tested by comparing battery capacity readings between upstream (mainline
> max17040 driver) and downstream (Samsung max17048_fuelgauge driver)
> across a full discharge cycle. Upstream reads ~3% lower throughout. Both
> track the discharge curve correctly:
> 
>   Upstream:   95 92 88 87 86 87 83 82 80 68 60 55 50 45 40 35 30 20 16 10 10 5 5 1
>   Downstream: 95 94 92 91 91 89 87 86 84 73 64 59 51 48 43 38 33 23 17 14 12 8 6 3
> 
> Each pair of readings was collected by checking the upstream capacity
> first, then moving the battery to a second expressatt running downstream
> Android to check its capacity. The battery was then moved back to the
> upstream device for the next reading. This swap occasionally caused the
> upstream capacity to read slightly higher than the previous value
> (e.g. 86 -> 87). When this happened, the reading was retaken after the
> value settled.

Ha, nice procedure!

Older phones used to chew through batteries on bootup, so perhaps that
could have had measurable impact as well..

[...]

> +&gsbi5_i2c {
> +	status = "okay";
> +
> +	fuel-gauge@36 {
> +		compatible = "maxim,max17048";
> +		reg = <0x36>;
> +		maxim,double-soc;
> +		maxim,rcomp = /bits/ 8 <0x62>;
> +		maxim,alert-low-soc-level = <2>;
> +		interrupt-parent = <&tlmm>;
> +		interrupts = <67 IRQ_TYPE_EDGE_FALLING>;

interrupts-extended = <&tlmm 67 IRQ...>

Reviewed-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>

Konrad