[PATCH v2 0/2] power: supply: max8903: add DC and USB input current-limit GPIO controls

[PATCH v2 0/2] power: supply: max8903: add DC and USB input current-limit GPIO controls

[Herman van Hazendonk via B4 Relay]

v2 addresses two rounds of reviewer feedback on v1.

Sebastian Reichel (1 finding):
 - Drop usb-current-limit-values DT property. The IUSB pin is
   silicon-fixed at 100/500 mA per the MAX8903 datasheet Pin
   Description ("Drive IUSB logic-low to set the USB current limit
   to 100mA. Drive IUSB logic-high to set the USB current limit to
   500mA."), so there's nothing board-specific to expose. The two
   values are bound to MAX8903_USB_CURRENT_LIMIT_{LOW,HIGH}_UA
   #defines in the driver with the datasheet quote in a header
   comment; usb-current-limit-gpios stays as the board parameter.

Kernel test robot / dt-schema reviewer (8 findings):
 - Binding: add dependentRequired so dc-current-limit-gpios and
   dc-current-limit-mapping are required together; incomplete DTs
   cannot pass dtschema with only one half of the pair.
 - Binding: rename example node "charger-with-current-limit" to the
   generic "charger" per the Devicetree Specification.
 - Driver get_property: when DC is online the hardware draws from
   DC regardless of USB state. Never fall through to reporting the
   USB cap; refuse with -ENODATA when DC GPIOs aren't configured
   rather than mis-describe the active source. The set path mirrors
   this policy.
 - Driver set_dc_current_limit: drop bitmap_from_arr32(values,
   &u32_var, 32). On 64-bit, the macro reinterprets its u32* source
   as unsigned long* and reads past the on-stack scalar; replace
   with bitmap_zero() + values[0] = gpio_value (the lowest ndescs
   bits, parse-time bounded to < 32).
 - Driver set_property: reject val->intval < 0 explicitly. The
   helpers take a u32 and a negative widen would bypass the upper
   bounds check, silently programming the maximum permitted current.
 - Driver IRQs: extend source_lock over the full
   read-modify-evaluate block in max8903_dcin() and max8903_usbin().
   With the old scope, simultaneous DC and USB plug events could
   race in the cen enable calculation and write the wrong bit.
 - Driver parse_dc_current_limit: switch the scratch map[] buffer
   from devm_kcalloc to kmalloc_array + explicit kfree on every
   return path; the buffer is only used during parse.
 - Driver parse_dc_current_limit: reject ndescs >= 32 at parse time
   to keep BIT(ndescs) well-defined on 32-bit. Defensive against a
   DT that somehow slipped past dtschema's maxItems=4 cap.

Tested on a HP TouchPad (APQ8060, MSM8x60 family) post-rework: all
4 interconnect fabrics still probe; max8903_charger enumerates and
binds; INPUT_CURRENT_LIMIT writes program the expected GPIO bit
patterns on both the DC resistor mux (verified against on-board
MAX8903B IDC wiring) and IUSB; USB link still up; no WARN/BUG/Oops.

The DTS hookup that wires these GPIOs to the MAX8903 on the HP
TouchPad will be sent separately to the ARM/DTS tree.

Signed-off-by: Herman van Hazendonk <github.com@herrie.org>
---
Herman van Hazendonk (2):
      dt-bindings: power: supply: maxim,max8903: add DC and USB input current-limit controls
      power: supply: max8903: add DC and USB input current-limit GPIO controls

 .../bindings/power/supply/maxim,max8903.yaml       |  53 +++
 drivers/power/supply/max8903_charger.c             | 415 ++++++++++++++++++++-
 2 files changed, 451 insertions(+), 17 deletions(-)
---
base-commit: 944125b4c454b58d2fe6e35f1087a932b2050dff
change-id: 20260605-submit-power-max8903-dc-limit-aa6e51a6c093

Best regards,
-- 
Herman van Hazendonk <github.com@herrie.org>

[PATCH v2 1/2] dt-bindings: power: supply: maxim,max8903: add DC and USB input current-limit controls

[Herman van Hazendonk via B4 Relay]

From: Herman van Hazendonk <github.com@herrie.org>

Add three optional properties to the MAX8903 charger binding to
describe board-level GPIO control of the DC and USB input current
limits:

DC input (TA / DOK pin):
  - dc-current-limit-gpios (1..4 GPIOs): mux control lines feeding
    the MAX8903 IDC resistor mux;
  - dc-current-limit-mapping (uint32-matrix of {microamps,
    gpio_bit_pattern} pairs): the available current levels and the
    GPIO bit pattern that selects each level.

USB input (USB / UOK pin):
  - usb-current-limit-gpios: a single GPIO driving the IUSB pin.
    The IUSB pin is silicon-fixed by the MAX8903 datasheet (Pin
    Description): low selects 100 mA, high selects 500 mA. Only
    the GPIO mapping is board-specific; the current values are
    not exposed in DT.

A dependentRequired block ties dc-current-limit-gpios and
dc-current-limit-mapping together so an incomplete DT cannot pass
validation with only one half of the pair.

These let userspace clamp the input draw via the standard
POWER_SUPPLY_PROP_INPUT_CURRENT_LIMIT power_supply attribute. The HP
TouchPad uses both: two TLMM lines select between 0.5 A, 1.0 A,
1.5 A and 2.0 A DC input current limits behind the MAX8903B
charger, and a third TLMM line picks the IUSB 100 mA / 500 mA
limit.

These are purely additive; existing platforms remain unaffected.

Signed-off-by: Herman van Hazendonk <github.com@herrie.org>
---
 .../bindings/power/supply/maxim,max8903.yaml       | 53 ++++++++++++++++++++++
 1 file changed, 53 insertions(+)

diff --git a/Documentation/devicetree/bindings/power/supply/maxim,max8903.yaml b/Documentation/devicetree/bindings/power/supply/maxim,max8903.yaml
index 86af38378999..b3d8c0a5f214 100644
--- a/Documentation/devicetree/bindings/power/supply/maxim,max8903.yaml
+++ b/Documentation/devicetree/bindings/power/supply/maxim,max8903.yaml
@@ -44,9 +44,40 @@ properties:
     maxItems: 1
     description: USB suspend pin (active high, output)
 
+  dc-current-limit-gpios:
+    minItems: 1
+    maxItems: 4
+    description:
+      GPIOs controlling DC input current limit via resistor mux.
+      Used with dc-current-limit-mapping to select charging current.
+
+  dc-current-limit-mapping:
+    $ref: /schemas/types.yaml#/definitions/uint32-matrix
+    minItems: 2
+    maxItems: 16
+    description: |
+      Array of (current_microamps, gpio_bit_pattern) pairs defining available
+      DC current limits. The gpio_bit_pattern is applied to dc-current-limit-gpios
+      to select that current level.
+    items:
+      items:
+        - description: Current limit in microamps
+        - description: GPIO bit pattern value
+
+  usb-current-limit-gpios:
+    maxItems: 1
+    description:
+      GPIO driving the MAX8903 IUSB pin. IUSB is a silicon-fixed
+      two-state input - low selects 100 mA, high selects 500 mA.
+      Only the GPIO mapping is board-specific.
+
 required:
   - compatible
 
+dependentRequired:
+  dc-current-limit-gpios: [dc-current-limit-mapping]
+  dc-current-limit-mapping: [dc-current-limit-gpios]
+
 anyOf:
   - required:
       - dok-gpios
@@ -65,3 +96,25 @@ examples:
       chg-gpios = <&gpio3 15 GPIO_ACTIVE_LOW>;
       cen-gpios = <&gpio2 5 GPIO_ACTIVE_LOW>;
     };
+  - |
+    /* Example with DC and USB current limit control */
+    #include <dt-bindings/gpio/gpio.h>
+    charger {
+      compatible = "maxim,max8903";
+      dok-gpios = <&gpio2 3 GPIO_ACTIVE_LOW>;
+      flt-gpios = <&gpio2 2 GPIO_ACTIVE_LOW>;
+      chg-gpios = <&gpio3 15 GPIO_ACTIVE_LOW>;
+      cen-gpios = <&gpio2 5 GPIO_ACTIVE_LOW>;
+      dcm-gpios = <&gpio2 6 GPIO_ACTIVE_HIGH>;
+
+      /* DC input current limit via IDC resistor mux */
+      dc-current-limit-gpios = <&gpio1 0 GPIO_ACTIVE_HIGH>,
+                               <&gpio1 1 GPIO_ACTIVE_HIGH>;
+      dc-current-limit-mapping = <750000 0>,  /* GPIO[1:0]=0b00 */
+                                 <900000 1>,  /* GPIO[1:0]=0b01 */
+                                 <1400000 3>, /* GPIO[1:0]=0b11 */
+                                 <2000000 2>; /* GPIO[1:0]=0b10 */
+
+      /* USB current limit: IUSB pin, 100 mA (low) / 500 mA (high) */
+      usb-current-limit-gpios = <&gpio1 2 GPIO_ACTIVE_HIGH>;
+    };

-- 
2.43.0

[PATCH v2 2/2] power: supply: max8903: add DC and USB input current-limit GPIO controls

[Herman van Hazendonk via B4 Relay]

From: Herman van Hazendonk <github.com@herrie.org>

Add two optional current-limit knobs surfaced through
POWER_SUPPLY_PROP_INPUT_CURRENT_LIMIT, selected by which input source
is currently online:

  - DC (DOK / TA-IN): a "dc-current-limit-gpios" array drives the
    GPIOs of an external resistor mux connected to the MAX8903 IDC pin
    (DC Current-Limit Set Input, pin 11). The IDC pin programs the
    step-down DC input current limit from 0.5 A to 2 A via R_IDC when
    the DCM mode pin is logic-high. The DT property
    "dc-current-limit-mapping" describes the (current_ua, gpio_value)
    pairs the board can program; the driver picks the largest entry
    whose limit is <= the requested limit. A 0 uA entry, used to
    stop drawing DC current, is selectable by issuing a 0 uA request
    (the selection uses a -1 "not found" sentinel rather than
    tracking best_limit > 0, so the all-zero entry can win).

  - USB (UOK / USB-IN): a single "usb-current-limit-gpio" drives the
    MAX8903 IUSB pin (USB Current-Limit Set Input, pin 7). The IUSB
    pin is silicon-fixed per the MAX8903 datasheet Pin Description:
    logic-low selects 100 mA, logic-high selects 500 mA. The two
    values are encoded as MAX8903_USB_CURRENT_LIMIT_{LOW,HIGH}_UA
    #defines with the datasheet quote in a header comment. The
    requested limit picks HIGH if it can absorb 500 mA, else LOW,
    else returns -EINVAL rather than silently programming a higher
    current that would violate the system power budget. Mirroring
    the DC-priority policy in the get path: when ta_in is asserted
    the part draws from DC regardless of USB state, so the set path
    only routes to USB when DC is not online.

The dispatch in max8903_set_property() to the DC vs USB path needs to
match the active source flag set by the corresponding *_ok GPIO IRQ
handler; both update sites take a new struct mutex source_lock so the
check and the resulting hardware write cannot be torn by a concurrent
IRQ flipping the source-online flag mid-decision. The DOK/UOK IRQ
handlers hold source_lock across the full read-modify-evaluate block
(line sampling, ta_in/usb_in update, dcm/cen GPIO writes, psy type
update) so the cen enable calculation reads a stable other-source
flag rather than racing with the peer IRQ. The IRQs are requested
with IRQF_ONESHOT (threaded), so a sleepable lock is the right
primitive in both contexts. max8903_get_property() also takes
source_lock briefly to snapshot the source flags and current-limit
values so userspace never observes a torn pair of
(source-online flag, current-limit ua).

dc-current-limit-mapping gpio_value entries are validated at parse
against the GPIO array width so a malformed DT value is rejected
instead of being silently truncated by gpiod_set_array_value() and
selecting the wrong mux level. ndescs is also bounded to
< BITS_PER_TYPE(u32) to keep BIT(ndescs) well-defined on 32-bit.
The mapping is additionally required to contain a gpio_value=0
entry: devm_gpiod_get_array_optional() asks for GPIOD_OUT_LOW, so
the hardware mux starts at gpio_value 0, and the driver seeds
dc_current_limit_ua from the matching map entry. A DT lacking the
all-zero entry is rejected with -EINVAL because otherwise the
reported INPUT_CURRENT_LIMIT could disagree with the mux state
until a set_property write picks a real value.

Negative INPUT_CURRENT_LIMIT requests are rejected at the
set_property entry: val->intval is signed, the set_*_current_limit()
helpers take a u32, and a negative cast would silently widen to a
huge unsigned value, bypass the upper-bound guard and program the
maximum permitted current.

Signed-off-by: Herman van Hazendonk <github.com@herrie.org>
---
 drivers/power/supply/max8903_charger.c | 415 +++++++++++++++++++++++++++++++--
 1 file changed, 398 insertions(+), 17 deletions(-)

diff --git a/drivers/power/supply/max8903_charger.c b/drivers/power/supply/max8903_charger.c
index 45fbaad6c647..97bd85f87eae 100644
--- a/drivers/power/supply/max8903_charger.c
+++ b/drivers/power/supply/max8903_charger.c
@@ -9,11 +9,29 @@
 #include <linux/gpio/consumer.h>
 #include <linux/interrupt.h>
 #include <linux/module.h>
+#include <linux/mutex.h>
 #include <linux/of.h>
+#include <linux/property.h>
 #include <linux/slab.h>
 #include <linux/power_supply.h>
 #include <linux/platform_device.h>
 
+/*
+ * IUSB pin: hardcoded by silicon to 100 mA (low) / 500 mA (high).
+ * MAX8903A/B/C/D/E/F/G/H/I datasheet, "Pin Description" table:
+ *   "USB Current-Limit Set Input. Drive IUSB logic-low to set the
+ *    USB current limit to 100mA. Drive IUSB logic-high to set the
+ *    USB current limit to 500mA."
+ * Not a board parameter - never DT-configurable.
+ */
+#define MAX8903_USB_CURRENT_LIMIT_LOW_UA	100000
+#define MAX8903_USB_CURRENT_LIMIT_HIGH_UA	500000
+
+struct max8903_current_limit_mapping {
+	u32 limit_ua;		/* Current limit in microamps */
+	u32 gpio_value;		/* GPIO bit pattern */
+};
+
 struct max8903_data {
 	struct device *dev;
 	struct power_supply *psy;
@@ -31,6 +49,25 @@ struct max8903_data {
 	struct gpio_desc *flt; /* Fault output */
 	struct gpio_desc *dcm; /* Current-Limit Mode input (1: DC, 2: USB) */
 	struct gpio_desc *usus; /* USB Suspend Input (1: suspended) */
+
+	/* DC current limit control (ISET pins) */
+	struct gpio_descs *dc_current_limit_gpios;
+	struct max8903_current_limit_mapping *dc_current_limit_map;
+	u32 dc_current_limit_map_size;
+	u32 dc_current_limit_ua;	/* Current setting in uA */
+
+	/* USB current limit control (IUSB pin) */
+	struct gpio_desc *usb_current_limit_gpio;
+	u32 usb_current_limit_ua;	/* Current setting in uA */
+
+	/*
+	 * Serialises ta_in / usb_in updates against
+	 * max8903_set_property() which steers the current-limit write to
+	 * the DC or USB path based on which source is currently online.
+	 * The IRQ handlers are requested with IRQF_ONESHOT (threaded), so
+	 * a sleepable mutex is the right primitive in both contexts.
+	 */
+	struct mutex source_lock;
 	bool fault;
 	bool usb_in;
 	bool ta_in;
@@ -40,6 +77,7 @@ static enum power_supply_property max8903_charger_props[] = {
 	POWER_SUPPLY_PROP_STATUS, /* Charger status output */
 	POWER_SUPPLY_PROP_ONLINE, /* External power source */
 	POWER_SUPPLY_PROP_HEALTH, /* Fault or OK */
+	POWER_SUPPLY_PROP_INPUT_CURRENT_LIMIT, /* Input current limit */
 };
 
 static int max8903_get_property(struct power_supply *psy,
@@ -47,6 +85,24 @@ static int max8903_get_property(struct power_supply *psy,
 		union power_supply_propval *val)
 {
 	struct max8903_data *data = power_supply_get_drvdata(psy);
+	bool ta_in, usb_in;
+	u32 dc_limit, usb_limit;
+
+	/*
+	 * Snapshot the source flags and current-limit settings under the
+	 * source_lock that the IRQs (max8903_dcin / max8903_usbin) and
+	 * max8903_set_property() take when updating them, so we never
+	 * observe a torn pair of (source-online flag, current-limit ua).
+	 * The gpiod_get_value() reads further down deliberately stay
+	 * outside the lock — they hit the GPIO controller, not driver
+	 * state, and the IRQs do not touch them under the lock either.
+	 */
+	mutex_lock(&data->source_lock);
+	ta_in = data->ta_in;
+	usb_in = data->usb_in;
+	dc_limit = data->dc_current_limit_ua;
+	usb_limit = data->usb_current_limit_ua;
+	mutex_unlock(&data->source_lock);
 
 	switch (psp) {
 	case POWER_SUPPLY_PROP_STATUS:
@@ -55,21 +111,42 @@ static int max8903_get_property(struct power_supply *psy,
 			if (gpiod_get_value(data->chg))
 				/* CHG asserted */
 				val->intval = POWER_SUPPLY_STATUS_CHARGING;
-			else if (data->usb_in || data->ta_in)
+			else if (usb_in || ta_in)
 				val->intval = POWER_SUPPLY_STATUS_NOT_CHARGING;
 			else
 				val->intval = POWER_SUPPLY_STATUS_DISCHARGING;
 		}
 		break;
 	case POWER_SUPPLY_PROP_ONLINE:
-		val->intval = 0;
-		if (data->usb_in || data->ta_in)
-			val->intval = 1;
+		val->intval = (ta_in || usb_in) ? 1 : 0;
 		break;
 	case POWER_SUPPLY_PROP_HEALTH:
-		val->intval = POWER_SUPPLY_HEALTH_GOOD;
-		if (data->fault)
-			val->intval = POWER_SUPPLY_HEALTH_UNSPEC_FAILURE;
+		/*
+		 * data->fault is a single bool toggled from one IRQ
+		 * handler, so a torn read is not possible; no need to
+		 * extend source_lock coverage here.
+		 */
+		val->intval = data->fault ? POWER_SUPPLY_HEALTH_UNSPEC_FAILURE
+					  : POWER_SUPPLY_HEALTH_GOOD;
+		break;
+	case POWER_SUPPLY_PROP_INPUT_CURRENT_LIMIT:
+		/*
+		 * Hardware prioritises DC over USB - when ta_in is asserted
+		 * the part draws from the DC input regardless of USB state.
+		 * So always report the DC-side limit when DC is online, and
+		 * refuse rather than silently fall back to the USB cap if
+		 * the DC GPIOs are not configured - that would mis-describe
+		 * the active source. Same policy applies in the set path.
+		 */
+		if (ta_in) {
+			if (!data->dc_current_limit_gpios)
+				return -ENODATA;
+			val->intval = dc_limit;
+		} else if (usb_in && data->usb_current_limit_gpio) {
+			val->intval = usb_limit;
+		} else {
+			return -ENODATA;
+		}
 		break;
 	default:
 		return -EINVAL;
@@ -78,6 +155,144 @@ static int max8903_get_property(struct power_supply *psy,
 	return 0;
 }
 
+static int max8903_set_dc_current_limit(struct max8903_data *data, u32 limit_ua)
+{
+	int i, best_idx = -1;
+	/*
+	 * The mapping's gpio_value fits in the lowest ndescs bits of one
+	 * unsigned long (parse_dc_current_limit enforces ndescs < 32 and
+	 * gpio_value < BIT(ndescs)); a single-word bitmap is sufficient
+	 * on both 32- and 64-bit builds. Don't use bitmap_from_arr32() -
+	 * that macro reinterprets its source pointer as unsigned long on
+	 * 64-bit and would read past the on-stack u32.
+	 */
+	DECLARE_BITMAP(values, BITS_PER_TYPE(u32));
+
+	if (!data->dc_current_limit_gpios)
+		return -EOPNOTSUPP;
+
+	/*
+	 * Find the highest supported current <= requested. Use a -1
+	 * "not found" sentinel rather than tracking best_limit > 0 so
+	 * that a 0 uA entry (used to disable charging) can be selected
+	 * by a 0 uA request.
+	 */
+	for (i = 0; i < data->dc_current_limit_map_size; i++) {
+		if (data->dc_current_limit_map[i].limit_ua > limit_ua)
+			continue;
+		if (best_idx < 0 ||
+		    data->dc_current_limit_map[i].limit_ua >
+				data->dc_current_limit_map[best_idx].limit_ua)
+			best_idx = i;
+	}
+
+	if (best_idx < 0)
+		return -EINVAL;
+
+	bitmap_zero(values, BITS_PER_TYPE(u32));
+	values[0] = data->dc_current_limit_map[best_idx].gpio_value;
+	gpiod_set_array_value_cansleep(data->dc_current_limit_gpios->ndescs,
+				       data->dc_current_limit_gpios->desc,
+				       data->dc_current_limit_gpios->info,
+				       values);
+
+	data->dc_current_limit_ua = data->dc_current_limit_map[best_idx].limit_ua;
+	dev_dbg(data->dev, "DC current limit set to %u uA\n",
+		data->dc_current_limit_ua);
+
+	return 0;
+}
+
+static int max8903_set_usb_current_limit(struct max8903_data *data, u32 limit_ua)
+{
+	u32 selected;
+	int gpio_val;
+
+	if (!data->usb_current_limit_gpio)
+		return -EOPNOTSUPP;
+
+	/*
+	 * IUSB is a single-bit input with two silicon-fixed settings;
+	 * pick HIGH (500 mA) iff the caller's cap can absorb it, else
+	 * LOW (100 mA), else refuse rather than program a higher current
+	 * than the request allows.
+	 */
+	if (limit_ua >= MAX8903_USB_CURRENT_LIMIT_HIGH_UA) {
+		selected = MAX8903_USB_CURRENT_LIMIT_HIGH_UA;
+		gpio_val = 1;
+	} else if (limit_ua >= MAX8903_USB_CURRENT_LIMIT_LOW_UA) {
+		selected = MAX8903_USB_CURRENT_LIMIT_LOW_UA;
+		gpio_val = 0;
+	} else {
+		return -EINVAL;
+	}
+
+	gpiod_set_value_cansleep(data->usb_current_limit_gpio, gpio_val);
+	data->usb_current_limit_ua = selected;
+
+	dev_dbg(data->dev, "USB current limit set to %u uA\n",
+		data->usb_current_limit_ua);
+
+	return 0;
+}
+
+static int max8903_set_property(struct power_supply *psy,
+		enum power_supply_property psp,
+		const union power_supply_propval *val)
+{
+	struct max8903_data *data = power_supply_get_drvdata(psy);
+	int ret;
+
+	switch (psp) {
+	case POWER_SUPPLY_PROP_INPUT_CURRENT_LIMIT:
+		/*
+		 * val->intval is signed; the set_*_current_limit() helpers
+		 * take a u32. Reject negatives explicitly so a negative
+		 * request cannot widen into a huge unsigned value, bypass
+		 * the "limit <= cap" bounds check inside the helper, and
+		 * silently program the maximum permitted current.
+		 */
+		if (val->intval < 0)
+			return -EINVAL;
+		/*
+		 * Hold source_lock across the source check and the
+		 * resulting hardware write so the IRQ handler cannot
+		 * flip ta_in/usb_in between them and have us program the
+		 * limit for a source that has just gone offline. Mirror
+		 * the DC-priority policy of the get path: if DC is online
+		 * route to the DC helper (refuse if DC GPIOs aren't
+		 * configured) rather than fall through to USB.
+		 */
+		mutex_lock(&data->source_lock);
+		if (data->ta_in)
+			ret = data->dc_current_limit_gpios ?
+			      max8903_set_dc_current_limit(data, val->intval) :
+			      -ENODEV;
+		else if (data->usb_in && data->usb_current_limit_gpio)
+			ret = max8903_set_usb_current_limit(data, val->intval);
+		else
+			ret = -EINVAL;
+		mutex_unlock(&data->source_lock);
+		return ret;
+	default:
+		return -EINVAL;
+	}
+}
+
+static int max8903_property_is_writeable(struct power_supply *psy,
+		enum power_supply_property psp)
+{
+	struct max8903_data *data = power_supply_get_drvdata(psy);
+
+	switch (psp) {
+	case POWER_SUPPLY_PROP_INPUT_CURRENT_LIMIT:
+		return data->dc_current_limit_gpios ||
+		       data->usb_current_limit_gpio;
+	default:
+		return 0;
+	}
+}
+
 static irqreturn_t max8903_dcin(int irq, void *_data)
 {
 	struct max8903_data *data = _data;
@@ -91,10 +306,21 @@ static irqreturn_t max8903_dcin(int irq, void *_data)
 	 * library as the line should be flagged GPIO_ACTIVE_LOW in the device
 	 * tree.
 	 */
+	/*
+	 * Hold source_lock across the full read-modify-evaluate block:
+	 *   - so a concurrent max8903_set_property() sees a consistent
+	 *     state (lock release would otherwise expose a window where
+	 *     data->ta_in is updated but the cen/dcm writes still pend);
+	 *   - so the cen enable calculation reads a stable data->usb_in
+	 *     rather than racing with max8903_usbin() and writing the
+	 *     wrong enable state.
+	 */
+	mutex_lock(&data->source_lock);
 	ta_in = gpiod_get_value(data->dok);
-
-	if (ta_in == data->ta_in)
+	if (ta_in == data->ta_in) {
+		mutex_unlock(&data->source_lock);
 		return IRQ_HANDLED;
+	}
 
 	data->ta_in = ta_in;
 
@@ -119,9 +345,6 @@ static irqreturn_t max8903_dcin(int irq, void *_data)
 		gpiod_set_value(data->cen, val);
 	}
 
-	dev_dbg(data->dev, "TA(DC-IN) Charger %s.\n", ta_in ?
-			"Connected" : "Disconnected");
-
 	old_type = data->psy_desc.type;
 
 	if (data->ta_in)
@@ -130,6 +353,10 @@ static irqreturn_t max8903_dcin(int irq, void *_data)
 		data->psy_desc.type = POWER_SUPPLY_TYPE_USB;
 	else
 		data->psy_desc.type = POWER_SUPPLY_TYPE_BATTERY;
+	mutex_unlock(&data->source_lock);
+
+	dev_dbg(data->dev, "TA(DC-IN) Charger %s.\n", ta_in ?
+			"Connected" : "Disconnected");
 
 	if (old_type != data->psy_desc.type)
 		power_supply_changed(data->psy);
@@ -150,10 +377,13 @@ static irqreturn_t max8903_usbin(int irq, void *_data)
 	 * library as the line should be flagged GPIO_ACTIVE_LOW in the device
 	 * tree.
 	 */
+	/* See max8903_dcin(): hold the lock across the full update. */
+	mutex_lock(&data->source_lock);
 	usb_in = gpiod_get_value(data->uok);
-
-	if (usb_in == data->usb_in)
+	if (usb_in == data->usb_in) {
+		mutex_unlock(&data->source_lock);
 		return IRQ_HANDLED;
+	}
 
 	data->usb_in = usb_in;
 
@@ -176,9 +406,6 @@ static irqreturn_t max8903_usbin(int irq, void *_data)
 		gpiod_set_value(data->cen, val);
 	}
 
-	dev_dbg(data->dev, "USB Charger %s.\n", usb_in ?
-			"Connected" : "Disconnected");
-
 	old_type = data->psy_desc.type;
 
 	if (data->ta_in)
@@ -187,6 +414,10 @@ static irqreturn_t max8903_usbin(int irq, void *_data)
 		data->psy_desc.type = POWER_SUPPLY_TYPE_USB;
 	else
 		data->psy_desc.type = POWER_SUPPLY_TYPE_BATTERY;
+	mutex_unlock(&data->source_lock);
+
+	dev_dbg(data->dev, "USB Charger %s.\n", usb_in ?
+			"Connected" : "Disconnected");
 
 	if (old_type != data->psy_desc.type)
 		power_supply_changed(data->psy);
@@ -221,6 +452,145 @@ static irqreturn_t max8903_fault(int irq, void *_data)
 	return IRQ_HANDLED;
 }
 
+static int max8903_parse_dc_current_limit(struct platform_device *pdev,
+					  struct max8903_data *data)
+{
+	struct device *dev = &pdev->dev;
+	int ret, i, map_size;
+	u32 *map;
+
+	data->dc_current_limit_gpios = devm_gpiod_get_array_optional(dev,
+					"dc-current-limit", GPIOD_OUT_LOW);
+	if (IS_ERR(data->dc_current_limit_gpios))
+		return dev_err_probe(dev, PTR_ERR(data->dc_current_limit_gpios),
+				     "failed to get DC current limit GPIOs");
+
+	if (!data->dc_current_limit_gpios)
+		return 0;	/* Optional feature not present */
+
+	/*
+	 * gpio_value entries below are bit patterns indexed into the
+	 * dc-current-limit GPIO array. The driver represents them in
+	 * a single unsigned long for gpiod_set_array_value_cansleep(),
+	 * and BIT(ndescs) further down assumes ndescs fits in a u32
+	 * shift; reject pathological DTs at parse time instead of
+	 * relying on undefined-behaviour-free dtschema. The binding
+	 * already caps maxItems at 4 so this is purely defensive.
+	 */
+	if (data->dc_current_limit_gpios->ndescs >= BITS_PER_TYPE(u32)) {
+		dev_err(dev, "dc-current-limit-gpios: %u GPIOs exceeds %u-bit cap\n",
+			data->dc_current_limit_gpios->ndescs,
+			(unsigned int)BITS_PER_TYPE(u32));
+		return -EINVAL;
+	}
+
+	/* Parse mapping: pairs of (current_ua, gpio_value) */
+	map_size = device_property_count_u32(dev, "dc-current-limit-mapping");
+	if (map_size <= 0 || map_size % 2) {
+		dev_err(dev, "invalid dc-current-limit-mapping\n");
+		return -EINVAL;
+	}
+
+	/*
+	 * map[] is a scratch buffer used only inside this function to
+	 * read the property and unpack it into data->dc_current_limit_map.
+	 * Use a plain kmalloc + kfree rather than devm_*: there is no
+	 * reason to keep the raw mirror around for the lifetime of the
+	 * device.
+	 */
+	map = kmalloc_array(map_size, sizeof(*map), GFP_KERNEL);
+	if (!map)
+		return -ENOMEM;
+
+	ret = device_property_read_u32_array(dev, "dc-current-limit-mapping",
+					     map, map_size);
+	if (ret) {
+		dev_err(dev, "failed to read dc-current-limit-mapping\n");
+		kfree(map);
+		return ret;
+	}
+
+	data->dc_current_limit_map_size = map_size / 2;
+	data->dc_current_limit_map = devm_kcalloc(dev,
+					data->dc_current_limit_map_size,
+					sizeof(*data->dc_current_limit_map),
+					GFP_KERNEL);
+	if (!data->dc_current_limit_map) {
+		kfree(map);
+		return -ENOMEM;
+	}
+
+	for (i = 0; i < data->dc_current_limit_map_size; i++) {
+		u32 gpio_value = map[i * 2 + 1];
+
+		/*
+		 * gpio_value is the bitmap programmed across the
+		 * dc-current-limit GPIOs, so it cannot represent more
+		 * bits than the GPIO array width. A larger value would
+		 * be silently truncated by gpiod_set_array_value() and
+		 * select the wrong limit; reject it at parse time so
+		 * the bogus DT is visible to the integrator.
+		 */
+		if (gpio_value >= BIT(data->dc_current_limit_gpios->ndescs)) {
+			dev_err(dev,
+				"dc-current-limit-mapping entry %d: gpio_value 0x%x exceeds %u-GPIO range\n",
+				i, gpio_value,
+				data->dc_current_limit_gpios->ndescs);
+			kfree(map);
+			return -EINVAL;
+		}
+		data->dc_current_limit_map[i].limit_ua = map[i * 2];
+		data->dc_current_limit_map[i].gpio_value = gpio_value;
+	}
+
+	kfree(map);
+
+	/*
+	 * devm_gpiod_get_array_optional() above asked for GPIOD_OUT_LOW,
+	 * so the hardware mux starts at gpio_value 0. Require the DT
+	 * mapping to include a gpio_value=0 entry so the software
+	 * current-limit state has a definite initial value matching the
+	 * hardware. Without this entry we would have to guess and the
+	 * reported INPUT_CURRENT_LIMIT could disagree with what the
+	 * mux is actually wired to until a set_property write picks a
+	 * real value.
+	 */
+	for (i = 0; i < data->dc_current_limit_map_size; i++)
+		if (data->dc_current_limit_map[i].gpio_value == 0)
+			break;
+	if (i == data->dc_current_limit_map_size) {
+		dev_err(dev,
+			"dc-current-limit-mapping must include a gpio_value=0 entry to describe the boot-time mux state\n");
+		return -EINVAL;
+	}
+	data->dc_current_limit_ua = data->dc_current_limit_map[i].limit_ua;
+
+	dev_dbg(dev, "DC current limit control: %d levels available, initial %u uA\n",
+		data->dc_current_limit_map_size, data->dc_current_limit_ua);
+
+	return 0;
+}
+
+static int max8903_parse_usb_current_limit(struct platform_device *pdev,
+					   struct max8903_data *data)
+{
+	struct device *dev = &pdev->dev;
+
+	data->usb_current_limit_gpio = devm_gpiod_get_optional(dev,
+					"usb-current-limit", GPIOD_OUT_LOW);
+	if (IS_ERR(data->usb_current_limit_gpio))
+		return dev_err_probe(dev, PTR_ERR(data->usb_current_limit_gpio),
+				     "failed to get USB current limit GPIO");
+
+	if (!data->usb_current_limit_gpio)
+		return 0;	/* Optional feature not present */
+
+	/* Start at low current (IUSB low = 100 mA) for safety */
+	data->usb_current_limit_ua = MAX8903_USB_CURRENT_LIMIT_LOW_UA;
+
+	return 0;
+}
+
 static int max8903_setup_gpios(struct platform_device *pdev)
 {
 	struct max8903_data *data = platform_get_drvdata(pdev);
@@ -335,17 +705,28 @@ static int max8903_probe(struct platform_device *pdev)
 		return -ENOMEM;
 
 	data->dev = dev;
+	mutex_init(&data->source_lock);
 	platform_set_drvdata(pdev, data);
 
 	ret = max8903_setup_gpios(pdev);
 	if (ret)
 		return ret;
 
+	ret = max8903_parse_dc_current_limit(pdev, data);
+	if (ret)
+		return ret;
+
+	ret = max8903_parse_usb_current_limit(pdev, data);
+	if (ret)
+		return ret;
+
 	data->psy_desc.name = "max8903_charger";
 	data->psy_desc.type = (data->ta_in) ? POWER_SUPPLY_TYPE_MAINS :
 			((data->usb_in) ? POWER_SUPPLY_TYPE_USB :
 			 POWER_SUPPLY_TYPE_BATTERY);
 	data->psy_desc.get_property = max8903_get_property;
+	data->psy_desc.set_property = max8903_set_property;
+	data->psy_desc.property_is_writeable = max8903_property_is_writeable;
 	data->psy_desc.properties = max8903_charger_props;
 	data->psy_desc.num_properties = ARRAY_SIZE(max8903_charger_props);
 

-- 
2.43.0

Re: [PATCH v2 1/2] dt-bindings: power: supply: maxim,max8903: add DC and USB input current-limit controls

[Rob Herring (Arm)]

On Fri, 05 Jun 2026 11:18:12 +0200, Herman van Hazendonk wrote:
> Add three optional properties to the MAX8903 charger binding to
> describe board-level GPIO control of the DC and USB input current
> limits:
> 
> DC input (TA / DOK pin):
>   - dc-current-limit-gpios (1..4 GPIOs): mux control lines feeding
>     the MAX8903 IDC resistor mux;
>   - dc-current-limit-mapping (uint32-matrix of {microamps,
>     gpio_bit_pattern} pairs): the available current levels and the
>     GPIO bit pattern that selects each level.
> 
> USB input (USB / UOK pin):
>   - usb-current-limit-gpios: a single GPIO driving the IUSB pin.
>     The IUSB pin is silicon-fixed by the MAX8903 datasheet (Pin
>     Description): low selects 100 mA, high selects 500 mA. Only
>     the GPIO mapping is board-specific; the current values are
>     not exposed in DT.
> 
> A dependentRequired block ties dc-current-limit-gpios and
> dc-current-limit-mapping together so an incomplete DT cannot pass
> validation with only one half of the pair.
> 
> These let userspace clamp the input draw via the standard
> POWER_SUPPLY_PROP_INPUT_CURRENT_LIMIT power_supply attribute. The HP
> TouchPad uses both: two TLMM lines select between 0.5 A, 1.0 A,
> 1.5 A and 2.0 A DC input current limits behind the MAX8903B
> charger, and a third TLMM line picks the IUSB 100 mA / 500 mA
> limit.
> 
> These are purely additive; existing platforms remain unaffected.
> 
> Signed-off-by: Herman van Hazendonk <github.com@herrie.org>
> ---
>  .../bindings/power/supply/maxim,max8903.yaml       | 53 ++++++++++++++++++++++
>  1 file changed, 53 insertions(+)
> 

Reviewed-by: Rob Herring (Arm) <robh@kernel.org>

Re: [PATCH v2 0/2] power: supply: max8903: add DC and USB input current-limit GPIO controls

[Sebastian Reichel]

On Fri, 05 Jun 2026 11:18:11 +0200, Herman van Hazendonk wrote:
> v2 addresses two rounds of reviewer feedback on v1.
> 
> Sebastian Reichel (1 finding):
>  - Drop usb-current-limit-values DT property. The IUSB pin is
>    silicon-fixed at 100/500 mA per the MAX8903 datasheet Pin
>    Description ("Drive IUSB logic-low to set the USB current limit
>    to 100mA. Drive IUSB logic-high to set the USB current limit to
>    500mA."), so there's nothing board-specific to expose. The two
>    values are bound to MAX8903_USB_CURRENT_LIMIT_{LOW,HIGH}_UA
>    #defines in the driver with the datasheet quote in a header
>    comment; usb-current-limit-gpios stays as the board parameter.
> 
> [...]

Applied, thanks!

[1/2] dt-bindings: power: supply: maxim,max8903: add DC and USB input current-limit controls
      commit: 353438b3107d56e36a642f117c2b4accc963abbd
[2/2] power: supply: max8903: add DC and USB input current-limit GPIO controls
      commit: 828414660052b629378764e5d5c1f07e60716a48

Best regards,
-- 
Sebastian Reichel <sebastian.reichel@collabora.com>