[PATCH v1 0/4] power: supply: bq25890: add input voltage limit

[PATCH v1 0/4] power: supply: bq25890: add input voltage limit

[Vincent Cloutier]

From: Vincent Cloutier <vincent@cloutier.co>

Hi,

Add an optional input-voltage-limit-microvolt firmware property for
selecting and programming an absolute VINDPM threshold. The Librem 5 uses
a BQ25895 charger; the board patch sets the 3.9 V threshold tested on the
phone. This provides useful standalone fixed-threshold configuration.

Purism's newer charging work pairs a 4.2 V threshold with Input Current
Optimizer support to improve operation with weak sources and resistive
cables. Those changes shipped in 6.12.79pureos1 as commit 3bd0fc6da9d0
("arm64: dts: imx8mq-librem5: Bump VINDPM to 4.2V") and commit ca7bb9bc4d24
("power: supply: bq25890: Support Input Current Optimizer"), and remain in
the inspected downstream 6.18 branches. That additional optimization is
follow-up work which can build on the generic configuration added here.

The BQ25896 resets FORCE_VINDPM and VINDPM when an input source is
inserted. Its source-detection and VINDPM-selection stages generate
separate interrupts, so the driver compares both fields with the requested
values whenever the charger is online, before returning for unchanged
charger state. It repeats the comparison during resume in case an input
insertion occurred while suspended. Registers are written only on a
mismatch, avoiding an interrupt loop. Successful restoration is reported as
a handled interrupt even when the tracked state is unchanged, without a
redundant power-supply change notification.

VINDPM programming and restoration require the explicit voltage-limit
property. linux,read-back-settings continues to bypass initialization
properties and does not enable restoration of a firmware-set threshold.

The binding and driver changes revisit this 2019 posting:
https://lore.kernel.org/all/20190520180712.32405-1-angus@akkea.ca/

This version addresses that review by using one property. Its presence
selects absolute VINDPM without supplying a default. The earlier review
suggested input-voltage-min-microvolt; the current bq256xx and sgm41542
bindings instead use input-voltage-limit-microvolt.

Patch 1 removes the invalid monitored-battery reference from the same
charger node. This cleanup is independent and can be applied separately.
It retains Angus Ainslie's original authorship and sign-off and adds my
submitter sign-off. Patches 2 through 4 are authored by me.

The series passes a focused arm64 W=1 driver build, BQ25890 binding and
example validation, Librem 5r2/r3/r4 DTB builds, and targeted CHECK_DTBS=y.
Host-side register-mock tests of the driver functions verify opt-in
behavior through initialization, online IRQ handling, and resume,
including read-back configurations with firmware-set absolute VINDPM.
They also check IRQ results, notification counts, and register I/O failures.
Earlier Librem 5r4 testing validated the property and BQ25895 board
setting: REG0D remained 0x8d on an attached boot, unplug, and flipped
replug. This validates initial BQ25895 programming and retention, but
cannot exercise the BQ25896 input-insertion restoration path. No BQ25896
hardware was available to test that path.

Angus Ainslie (Purism) (1):
  arm64: dts: imx8mq-librem5: Remove invalid monitored-battery

Vincent Cloutier (3):
  dt-bindings: power: supply: bq25890: Add input voltage limit
  power: supply: bq25890: Add input voltage limit
  arm64: dts: imx8mq-librem5: Set BQ25895 input voltage limit

 .../devicetree/bindings/power/supply/bq25890.yaml  |  9 +++
 arch/arm64/boot/dts/freescale/imx8mq-librem5.dtsi  |  2 +-
 drivers/power/supply/bq25890_charger.c             | 74 +++++++++++++++++++++-
 3 files changed, 83 insertions(+), 2 deletions(-)


base-commit: 4477a78374a57c3809b172ad30cceabda48c47c6
-- 
2.55.0

[PATCH v1 1/4] arm64: dts: imx8mq-librem5: Remove invalid monitored-battery

[Vincent Cloutier]

From: "Angus Ainslie (Purism)" <angus@akkea.ca>

The BQ25895 charger node points monitored-battery at the MAX17055 fuel
gauge. The property requires a phandle to a simple-battery node, and the
upstream BQ25890 driver does not consume battery information.

Remove the invalid relationship.

Fixes: 8f0216b006e5 ("arm64: dts: Add a device tree for the Librem 5 phone")
Signed-off-by: Angus Ainslie (Purism) <angus@akkea.ca>
Signed-off-by: Vincent Cloutier <vincent@cloutier.co>
---
 arch/arm64/boot/dts/freescale/imx8mq-librem5.dtsi | 1 -
 1 file changed, 1 deletion(-)

diff --git a/arch/arm64/boot/dts/freescale/imx8mq-librem5.dtsi b/arch/arm64/boot/dts/freescale/imx8mq-librem5.dtsi
index f5d529c5baf3..099195279e84 100644
--- a/arch/arm64/boot/dts/freescale/imx8mq-librem5.dtsi
+++ b/arch/arm64/boot/dts/freescale/imx8mq-librem5.dtsi
@@ -1201,7 +1201,6 @@ bq25895: charger@6a {
 		ti,minimum-sys-voltage = <3700000>; /* uV */
 		ti,boost-voltage = <5000000>; /* uV */
 		ti,boost-max-current = <1500000>; /* uA */
-		monitored-battery = <&bat>;
 		power-supplies = <&typec_pd>;
 	};
 };
-- 
2.55.0

[PATCH v1 2/4] dt-bindings: power: supply: bq25890: Add input voltage limit

[Vincent Cloutier]

From: Vincent Cloutier <vincent@cloutier.co>

Document input-voltage-limit-microvolt for configuring the absolute input
voltage dynamic power management threshold. When the property is absent,
the charger retains its relative VINDPM behavior.

Assisted-by: OpenCode:gpt-5.6-sol
Signed-off-by: Vincent Cloutier <vincent@cloutier.co>
---
 .../devicetree/bindings/power/supply/bq25890.yaml        | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/Documentation/devicetree/bindings/power/supply/bq25890.yaml b/Documentation/devicetree/bindings/power/supply/bq25890.yaml
index 0ad302ab2bcc..8d1f27447cca 100644
--- a/Documentation/devicetree/bindings/power/supply/bq25890.yaml
+++ b/Documentation/devicetree/bindings/power/supply/bq25890.yaml
@@ -31,6 +31,14 @@ properties:
   interrupts:
     maxItems: 1
 
+  input-voltage-limit-microvolt:
+    description: |
+      Absolute input voltage limit. When present, the charger uses the
+      absolute VINDPM threshold instead of relative VINDPM.
+    minimum: 3900000
+    maximum: 14000000
+    multipleOf: 100000
+
   ti,battery-regulation-voltage:
     $ref: /schemas/types.yaml#/definitions/uint32
     description: maximum charging voltage (in uV)
@@ -113,6 +121,7 @@ examples:
         interrupt-parent = <&gpio1>;
         interrupts = <16 IRQ_TYPE_EDGE_FALLING>;
 
+        input-voltage-limit-microvolt = <3900000>;
         ti,battery-regulation-voltage = <4200000>;
         ti,charge-current = <1000000>;
         ti,termination-current = <50000>;
-- 
2.55.0

[PATCH v1 3/4] power: supply: bq25890: Add input voltage limit

[Vincent Cloutier]

From: Vincent Cloutier <vincent@cloutier.co>

The BQ25890 family supports an absolute input voltage dynamic power
management threshold. Read input-voltage-limit-microvolt from firmware,
enable absolute VINDPM, and then program the requested threshold. Only
program and restore VINDPM when this property is parsed. Without it,
retain the existing VINDPM behavior.

As with the other initialization properties, linux,read-back-settings
bypasses parsing this property. Do not read back VINDPM into the requested
settings, so a firmware-configured absolute threshold does not implicitly
enable restoration.

The BQ25896 resets FORCE_VINDPM and VINDPM when an input source is
inserted. Source detection and VINDPM threshold selection generate
separate interrupts, so compare the fields with the requested values on
every online state refresh before returning for unchanged charger state.
Restore them only when they differ to avoid an interrupt loop. Report a
successful restoration as a handled interrupt even when the tracked state
is unchanged, without sending a redundant power-supply change notification.

Repeat the comparison during resume because an input insertion while
suspended may not leave a visible offline-to-online transition.

The BQ25896-specific restoration path has not been tested on hardware.

Assisted-by: OpenCode:gpt-5.6-sol
Assisted-by: OpenCode:gpt-6-astra
Signed-off-by: Vincent Cloutier <vincent@cloutier.co>
---
 drivers/power/supply/bq25890_charger.c | 74 +++++++++++++++++++++++++-
 1 file changed, 73 insertions(+), 1 deletion(-)

diff --git a/drivers/power/supply/bq25890_charger.c b/drivers/power/supply/bq25890_charger.c
index 741a45cc5f35..71d6cf179667 100644
--- a/drivers/power/supply/bq25890_charger.c
+++ b/drivers/power/supply/bq25890_charger.c
@@ -88,6 +88,8 @@ struct bq25890_init_data {
 	u8 boosti;	/* boost current limit		*/
 	u8 boostf;	/* boost frequency		*/
 	u8 ilim_en;	/* enable ILIM pin		*/
+	bool force_vindpm; /* explicit absolute VINDPM request */
+	u8 vindpm;	/* absolute VINDPM threshold	*/
 	u8 treg;	/* thermal regulation threshold */
 	u8 rbatcomp;	/* IBAT sense resistor value    */
 	u8 vclamp;	/* IBAT compensation voltage limit */
@@ -284,6 +286,7 @@ enum bq25890_table_ids {
 	TBL_VBUSV,
 	TBL_VBATCOMP,
 	TBL_RBATCOMP,
+	TBL_VINDPM,
 
 	/* lookup tables */
 	TBL_TREG,
@@ -351,6 +354,7 @@ static const union {
 	[TBL_VBUSV] =	 { .rt = {2600000, 15300000, 100000} },	 /* uV */
 	[TBL_VBATCOMP] = { .rt = {0,         224000, 32000} },	 /* uV */
 	[TBL_RBATCOMP] = { .rt = {0,         140000, 20000} },	 /* uOhm */
+	[TBL_VINDPM] =   { .rt = {2600000, 15300000, 100000} },	 /* uV */
 
 	/* lookup tables */
 	[TBL_TREG] =	{ .lt = {bq25890_treg_tbl, BQ25890_TREG_TBL_SIZE} },
@@ -814,18 +818,67 @@ static int bq25890_get_chip_state(struct bq25890_device *bq,
 	return 0;
 }
 
+static int bq25890_set_vindpm(struct bq25890_device *bq)
+{
+	int ret;
+
+	if (!bq->init_data.force_vindpm)
+		return 0;
+
+	ret = bq25890_field_write(bq, F_FORCE_VINDPM, 1);
+	if (ret < 0)
+		return ret;
+
+	return bq25890_field_write(bq, F_VINDPM, bq->init_data.vindpm);
+}
+
+/* Return 1 if restored, 0 if unchanged, or a negative error. */
+static int bq25890_restore_vindpm(struct bq25890_device *bq)
+{
+	int force, vindpm, ret;
+
+	if (!bq->init_data.force_vindpm || bq->chip_version != BQ25896)
+		return 0;
+
+	force = bq25890_field_read(bq, F_FORCE_VINDPM);
+	if (force < 0)
+		return force;
+
+	vindpm = bq25890_field_read(bq, F_VINDPM);
+	if (vindpm < 0)
+		return vindpm;
+
+	if (force && vindpm == bq->init_data.vindpm)
+		return 0;
+
+	ret = bq25890_set_vindpm(bq);
+	if (ret < 0)
+		return ret;
+
+	return 1;
+}
+
 static irqreturn_t __bq25890_handle_irq(struct bq25890_device *bq)
 {
 	bool adc_conv_rate, new_adc_conv_rate;
 	struct bq25890_state new_state;
+	irqreturn_t irq_ret = IRQ_NONE;
 	int ret;
 
 	ret = bq25890_get_chip_state(bq, &new_state);
 	if (ret < 0)
 		return IRQ_NONE;
 
+	if (new_state.online) {
+		ret = bq25890_restore_vindpm(bq);
+		if (ret < 0)
+			goto error;
+		if (ret > 0)
+			irq_ret = IRQ_HANDLED;
+	}
+
 	if (!memcmp(&bq->state, &new_state, sizeof(new_state)))
-		return IRQ_NONE;
+		return irq_ret;
 
 	/*
 	 * Restore HiZ bit in case it was set by user. The chip does not retain
@@ -932,6 +985,9 @@ static int bq25890_rw_init_data(struct bq25890_device *bq)
 		}
 	}
 
+	if (write)
+		return bq25890_set_vindpm(bq);
+
 	return 0;
 }
 
@@ -1386,6 +1442,18 @@ static int bq25890_fw_read_u32_props(struct bq25890_device *bq)
 						       props[i].tbl_id);
 	}
 
+	if (device_property_present(bq->dev,
+				    "input-voltage-limit-microvolt")) {
+		ret = device_property_read_u32(bq->dev,
+					       "input-voltage-limit-microvolt",
+					       &property);
+		if (ret < 0)
+			return ret;
+
+		init->vindpm = bq25890_find_idx(property, TBL_VINDPM);
+		init->force_vindpm = true;
+	}
+
 	return 0;
 }
 
@@ -1609,6 +1677,10 @@ static int bq25890_resume(struct device *dev)
 
 	/* Re-enable ADC only if charger is plugged in. */
 	if (bq->state.online) {
+		ret = bq25890_restore_vindpm(bq);
+		if (ret < 0)
+			goto unlock;
+
 		ret = bq25890_field_write(bq, F_CONV_RATE, 1);
 		if (ret < 0)
 			goto unlock;
-- 
2.55.0

[PATCH v1 4/4] arm64: dts: imx8mq-librem5: Set BQ25895 input voltage limit

[Vincent Cloutier]

From: Vincent Cloutier <vincent@cloutier.co>

Purism's production Librem 5 kernels used a 3.9 V absolute VINDPM
threshold for years, from the 2019 board support through the releases
preceding the March 2026 charging update. Use this established board
setting for the BQ25895 input voltage limit.

Set input-voltage-limit-microvolt to 3900000 to select absolute VINDPM
and program the 3.9 V threshold through the generic binding.

Tested on Librem 5r4: REG0D remained 0x8d across an attached boot, unplug,
and flipped replug.

Assisted-by: OpenCode:gpt-5.6-sol
Assisted-by: OpenCode:gpt-6-astra
Signed-off-by: Vincent Cloutier <vincent@cloutier.co>
---
 arch/arm64/boot/dts/freescale/imx8mq-librem5.dtsi | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/arm64/boot/dts/freescale/imx8mq-librem5.dtsi b/arch/arm64/boot/dts/freescale/imx8mq-librem5.dtsi
index 099195279e84..8badebfcdbb4 100644
--- a/arch/arm64/boot/dts/freescale/imx8mq-librem5.dtsi
+++ b/arch/arm64/boot/dts/freescale/imx8mq-librem5.dtsi
@@ -1195,6 +1195,7 @@ bq25895: charger@6a {
 		pinctrl-0 = <&pinctrl_charger_in>;
 		interrupt-parent = <&gpio3>;
 		interrupts = <3 IRQ_TYPE_EDGE_FALLING>;
+		input-voltage-limit-microvolt = <3900000>;
 		ti,battery-regulation-voltage = <4208000>; /* uV */
 		ti,termination-current = <128000>;  /* uA */
 		ti,precharge-current = <128000>; /* uA */
-- 
2.55.0

Re: [PATCH v1 2/4] dt-bindings: power: supply: bq25890: Add input voltage limit

[Conor Dooley]

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Acked-by: Conor Dooley <conor.dooley@microchip.com>
pw-bot: not-applicable

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Re: [PATCH v1 4/4] arm64: dts: imx8mq-librem5: Set BQ25895 input voltage limit

[Sebastian Krzyszkowiak]

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On niedziela, 27 września 2026 16:55:38 czas środkowoeuropejski letni Vincent 
Cloutier wrote:
> From: Vincent Cloutier <vincent@cloutier.co>
> 
> Purism's production Librem 5 kernels used a 3.9 V absolute VINDPM
> threshold for years,

...because it was (likely accidentally) left over from the devkit dts where it 
was genuinely needed.

> from the 2019 board support through the releases
> preceding the March 2026 charging update.

...which is when it was changed because it was found to be the cause of issues 
due to interactions between TPS65982 and BQ25895 cut-off limits observed when 
used with power sources that struggle to provide the required voltage when 
under load.

> Use this established board
> setting for the BQ25895 input voltage limit.

Why? What makes you want to bring the bad value upstream?

> Set input-voltage-limit-microvolt to 3900000 to select absolute VINDPM
> and program the 3.9 V threshold through the generic binding.
> 
> Tested on Librem 5r4: REG0D remained 0x8d across an attached boot, unplug,
> and flipped replug.
> 
> Assisted-by: OpenCode:gpt-5.6-sol
> Assisted-by: OpenCode:gpt-6-astra
> Signed-off-by: Vincent Cloutier <vincent@cloutier.co>
> ---
>  arch/arm64/boot/dts/freescale/imx8mq-librem5.dtsi | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/arch/arm64/boot/dts/freescale/imx8mq-librem5.dtsi
> b/arch/arm64/boot/dts/freescale/imx8mq-librem5.dtsi index
> 099195279e84..8badebfcdbb4 100644
> --- a/arch/arm64/boot/dts/freescale/imx8mq-librem5.dtsi
> +++ b/arch/arm64/boot/dts/freescale/imx8mq-librem5.dtsi
> @@ -1195,6 +1195,7 @@ bq25895: charger@6a {
>  		pinctrl-0 = <&pinctrl_charger_in>;
>  		interrupt-parent = <&gpio3>;
>  		interrupts = <3 IRQ_TYPE_EDGE_FALLING>;
> +		input-voltage-limit-microvolt = <3900000>;
>  		ti,battery-regulation-voltage = <4208000>; /* uV */
>  		ti,termination-current = <128000>;  /* uA */
>  		ti,precharge-current = <128000>; /* uA */


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