power: supply: Add pm8916 VM-BMS support

This driver adds basic support for VM-BMS found in pm8916.

VM-BMS is a very basic fuel-gauge hardware block that is, sadly,
incapable of any gauging. The hardware supports measuring OCV in
sleep mode, where the battery is not in use, or measuring average
voltage over time when the device is active.

This driver implements basic value readout from this block.

Signed-off-by: Nikita Travkin <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Sebastian Reichel <[e-mail]>

drivers/power/supply/Kconfig

···
 	  documentation for more detail.  The base name for this driver is
 	  'pm8941_charger'.
 
+config BATTERY_PM8916_BMS_VM
+	tristate "Qualcomm PM8916 BMS-VM support"
+	depends on MFD_SPMI_PMIC || COMPILE_TEST
+	help
+	  Say Y to add support for Voltage Mode BMS block found in some
+	  Qualcomm PMICs such as PM8916. This hardware block provides
+	  battery voltage monitoring for the system.
+
+	  To compile this driver as module, choose M here: the
+	  module will be called pm8916_bms_vm.
+
 config CHARGER_BQ2415X
 	tristate "TI BQ2415x battery charger driver"
 	depends on I2C

drivers/power/supply/Makefile

···
 obj-$(CONFIG_CHARGER_MT6360)	+= mt6360_charger.o
 obj-$(CONFIG_CHARGER_MT6370)	+= mt6370-charger.o
 obj-$(CONFIG_CHARGER_QCOM_SMBB)	+= qcom_smbb.o
+obj-$(CONFIG_BATTERY_PM8916_BMS_VM)	+= pm8916_bms_vm.o
 obj-$(CONFIG_CHARGER_BQ2415X)	+= bq2415x_charger.o
 obj-$(CONFIG_CHARGER_BQ24190)	+= bq24190_charger.o
 obj-$(CONFIG_CHARGER_BQ24257)	+= bq24257_charger.o

drivers/power/supply/pm8916_bms_vm.c

···
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2023, Nikita Travkin <[e-mail]>
+ */
+
+#include <linux/errno.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/power_supply.h>
+#include <linux/property.h>
+#include <linux/regmap.h>
+#include <linux/slab.h>
+#include <linux/delay.h>
+#include <linux/interrupt.h>
+#include <linux/timekeeping.h>
+#include <linux/mod_devicetable.h>
+
+#define PM8916_PERPH_TYPE 0x04
+#define PM8916_BMS_VM_TYPE 0x020D
+
+#define PM8916_SEC_ACCESS 0xD0
+#define PM8916_SEC_MAGIC 0xA5
+
+#define PM8916_BMS_VM_STATUS1 0x08
+#define PM8916_BMS_VM_FSM_STATE(x) (((x) & 0b00111000) >> 3)
+#define PM8916_BMS_VM_FSM_STATE_S2 0x2
+
+#define PM8916_BMS_VM_MODE_CTL 0x40
+#define PM8916_BMS_VM_MODE_FORCE_S3 (BIT(0) | BIT(1))
+#define PM8916_BMS_VM_MODE_NORMAL (BIT(1) | BIT(3))
+
+#define PM8916_BMS_VM_EN_CTL 0x46
+#define PM8916_BMS_ENABLED BIT(7)
+
+#define PM8916_BMS_VM_FIFO_LENGTH_CTL 0x47
+#define PM8916_BMS_VM_S1_SAMPLE_INTERVAL_CTL 0x55
+#define PM8916_BMS_VM_S2_SAMPLE_INTERVAL_CTL 0x56
+#define PM8916_BMS_VM_S3_S7_OCV_DATA0 0x6A
+#define PM8916_BMS_VM_BMS_FIFO_REG_0_LSB 0xC0
+
+/* Using only 1 fifo is broken in hardware */
+#define PM8916_BMS_VM_FIFO_COUNT 2 /* 2 .. 8 */
+
+#define PM8916_BMS_VM_S1_SAMPLE_INTERVAL 10
+#define PM8916_BMS_VM_S2_SAMPLE_INTERVAL 10
+
+struct pm8916_bms_vm_battery {
+	struct device *dev;
+	struct power_supply *battery;
+	struct power_supply_battery_info *info;
+	struct regmap *regmap;
+	unsigned int reg;
+	unsigned int last_ocv;
+	time64_t last_ocv_time;
+	unsigned int vbat_now;
+};
+
+static int pm8916_bms_vm_battery_get_property(struct power_supply *psy,
+					      enum power_supply_property psp,
+					      union power_supply_propval *val)
+{
+	struct pm8916_bms_vm_battery *bat = power_supply_get_drvdata(psy);
+	struct power_supply_battery_info *info = bat->info;
+	int supplied;
+
+	switch (psp) {
+	case POWER_SUPPLY_PROP_STATUS:
+		supplied = power_supply_am_i_supplied(psy);
+
+		if (supplied < 0 && supplied != -ENODEV)
+			return supplied;
+		else if (supplied && supplied != -ENODEV)
+			val->intval = POWER_SUPPLY_STATUS_CHARGING;
+		else
+			val->intval = POWER_SUPPLY_STATUS_DISCHARGING;
+		return 0;
+
+	case POWER_SUPPLY_PROP_HEALTH:
+		if (bat->vbat_now < info->voltage_min_design_uv)
+			val->intval = POWER_SUPPLY_HEALTH_DEAD;
+		else if (bat->vbat_now > info->voltage_max_design_uv)
+			val->intval = POWER_SUPPLY_HEALTH_OVERVOLTAGE;
+		else
+			val->intval = POWER_SUPPLY_HEALTH_GOOD;
+		return 0;
+
+	case POWER_SUPPLY_PROP_VOLTAGE_NOW:
+		val->intval = bat->vbat_now;
+		return 0;
+
+	case POWER_SUPPLY_PROP_VOLTAGE_OCV:
+		/*
+		 * Hardware only reliably measures OCV when the system is off or suspended.
+		 * We expose the last known OCV value on boot, invalidating it after 180 seconds.
+		 */
+		if (ktime_get_seconds() - bat->last_ocv_time > 180)
+			return -ENODATA;
+
+		val->intval = bat->last_ocv;
+		return 0;
+
+	default:
+		return -EINVAL;
+	}
+}
+
+static enum power_supply_property pm8916_bms_vm_battery_properties[] = {
+	POWER_SUPPLY_PROP_STATUS,
+	POWER_SUPPLY_PROP_VOLTAGE_NOW,
+	POWER_SUPPLY_PROP_VOLTAGE_OCV,
+	POWER_SUPPLY_PROP_HEALTH,
+};
+
+static irqreturn_t pm8916_bms_vm_fifo_update_done_irq(int irq, void *data)
+{
+	struct pm8916_bms_vm_battery *bat = data;
+	u16 vbat_data[PM8916_BMS_VM_FIFO_COUNT];
+	int ret;
+
+	ret = regmap_bulk_read(bat->regmap, bat->reg + PM8916_BMS_VM_BMS_FIFO_REG_0_LSB,
+			       &vbat_data, PM8916_BMS_VM_FIFO_COUNT * 2);
+	if (ret)
+		return IRQ_HANDLED;
+
+	/*
+	 * The VM-BMS hardware only collects voltage data and the software
+	 * has to process it to calculate the OCV and SoC. Hardware provides
+	 * up to 8 averaged measurements for software to take in account.
+	 *
+	 * Just use the last measured value for now to report the current
+	 * battery voltage.
+	 */
+	bat->vbat_now = vbat_data[PM8916_BMS_VM_FIFO_COUNT - 1] * 300;
+
+	power_supply_changed(bat->battery);
+
+	return IRQ_HANDLED;
+}
+
+static const struct power_supply_desc pm8916_bms_vm_battery_psy_desc = {
+	.name = "pm8916-bms-vm",
+	.type = POWER_SUPPLY_TYPE_BATTERY,
+	.properties = pm8916_bms_vm_battery_properties,
+	.num_properties = ARRAY_SIZE(pm8916_bms_vm_battery_properties),
+	.get_property = pm8916_bms_vm_battery_get_property,
+};
+
+static int pm8916_bms_vm_battery_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct pm8916_bms_vm_battery *bat;
+	struct power_supply_config psy_cfg = {};
+	int ret, irq;
+	unsigned int tmp;
+
+	bat = devm_kzalloc(dev, sizeof(*bat), GFP_KERNEL);
+	if (!bat)
+		return -ENOMEM;
+
+	bat->dev = dev;
+
+	bat->regmap = dev_get_regmap(pdev->dev.parent, NULL);
+	if (!bat->regmap)
+		return -ENODEV;
+
+	ret = device_property_read_u32(dev, "reg", &bat->reg);
+	if (ret < 0)
+		return -EINVAL;
+
+	irq = platform_get_irq_byname(pdev, "fifo");
+	if (irq < 0)
+		return irq;
+
+	ret = devm_request_threaded_irq(dev, irq, NULL, pm8916_bms_vm_fifo_update_done_irq,
+					IRQF_ONESHOT, "pm8916_vm_bms", bat);
+	if (ret)
+		return ret;
+
+	ret = regmap_bulk_read(bat->regmap, bat->reg + PM8916_PERPH_TYPE, &tmp, 2);
+	if (ret)
+		goto comm_error;
+
+	if (tmp != PM8916_BMS_VM_TYPE)
+		return dev_err_probe(dev, -ENODEV, "Device reported wrong type: 0x%X\n", tmp);
+
+	ret = regmap_write(bat->regmap, bat->reg + PM8916_BMS_VM_S1_SAMPLE_INTERVAL_CTL,
+			   PM8916_BMS_VM_S1_SAMPLE_INTERVAL);
+	if (ret)
+		goto comm_error;
+	ret = regmap_write(bat->regmap, bat->reg + PM8916_BMS_VM_S2_SAMPLE_INTERVAL_CTL,
+			   PM8916_BMS_VM_S2_SAMPLE_INTERVAL);
+	if (ret)
+		goto comm_error;
+	ret = regmap_write(bat->regmap, bat->reg + PM8916_BMS_VM_FIFO_LENGTH_CTL,
+			   PM8916_BMS_VM_FIFO_COUNT << 4 | PM8916_BMS_VM_FIFO_COUNT);
+	if (ret)
+		goto comm_error;
+	ret = regmap_write(bat->regmap,
+			   bat->reg + PM8916_BMS_VM_EN_CTL, PM8916_BMS_ENABLED);
+	if (ret)
+		goto comm_error;
+
+	ret = regmap_bulk_read(bat->regmap,
+			       bat->reg + PM8916_BMS_VM_S3_S7_OCV_DATA0, &tmp, 2);
+	if (ret)
+		goto comm_error;
+
+	bat->last_ocv_time = ktime_get_seconds();
+	bat->last_ocv = tmp * 300;
+	bat->vbat_now = bat->last_ocv;
+
+	psy_cfg.drv_data = bat;
+	psy_cfg.of_node = dev->of_node;
+
+	bat->battery = devm_power_supply_register(dev, &pm8916_bms_vm_battery_psy_desc, &psy_cfg);
+	if (IS_ERR(bat->battery))
+		return dev_err_probe(dev, PTR_ERR(bat->battery), "Unable to register battery\n");
+
+	ret = power_supply_get_battery_info(bat->battery, &bat->info);
+	if (ret)
+		return dev_err_probe(dev, ret, "Unable to get battery info\n");
+
+	platform_set_drvdata(pdev, bat);
+
+	return 0;
+
+comm_error:
+	return dev_err_probe(dev, ret, "Unable to communicate with device\n");
+}
+
+static int pm8916_bms_vm_battery_suspend(struct platform_device *pdev, pm_message_t state)
+{
+	struct pm8916_bms_vm_battery *bat = platform_get_drvdata(pdev);
+	int ret;
+
+	/*
+	 * Due to a hardware quirk the FSM doesn't switch states normally.
+	 * Instead we unlock the debug registers and force S3 (Measure OCV/Sleep)
+	 * mode every time we suspend.
+	 */
+
+	ret = regmap_write(bat->regmap,
+			   bat->reg + PM8916_SEC_ACCESS, PM8916_SEC_MAGIC);
+	if (ret)
+		goto error;
+	ret = regmap_write(bat->regmap,
+			   bat->reg + PM8916_BMS_VM_MODE_CTL, PM8916_BMS_VM_MODE_FORCE_S3);
+	if (ret)
+		goto error;
+
+	return 0;
+
+error:
+	dev_err(bat->dev, "Failed to force S3 mode: %pe\n", ERR_PTR(ret));
+	return ret;
+}
+
+static int pm8916_bms_vm_battery_resume(struct platform_device *pdev)
+{
+	struct pm8916_bms_vm_battery *bat = platform_get_drvdata(pdev);
+	int ret;
+	unsigned int tmp;
+
+	ret = regmap_bulk_read(bat->regmap,
+			       bat->reg + PM8916_BMS_VM_S3_S7_OCV_DATA0, &tmp, 2);
+
+	bat->last_ocv_time = ktime_get_seconds();
+	bat->last_ocv = tmp * 300;
+
+	ret = regmap_write(bat->regmap,
+			   bat->reg + PM8916_SEC_ACCESS, PM8916_SEC_MAGIC);
+	if (ret)
+		goto error;
+	ret = regmap_write(bat->regmap,
+			   bat->reg + PM8916_BMS_VM_MODE_CTL, PM8916_BMS_VM_MODE_NORMAL);
+	if (ret)
+		goto error;
+
+	return 0;
+
+error:
+	dev_err(bat->dev, "Failed to return normal mode: %pe\n", ERR_PTR(ret));
+	return ret;
+}
+
+static const struct of_device_id pm8916_bms_vm_battery_of_match[] = {
+	{ .compatible = "qcom,pm8916-bms-vm", },
+	{}
+};
+MODULE_DEVICE_TABLE(of, pm8916_bms_vm_battery_of_match);
+
+static struct platform_driver pm8916_bms_vm_battery_driver = {
+	.driver = {
+		.name = "pm8916-bms-vm",
+		.of_match_table = pm8916_bms_vm_battery_of_match,
+	},
+	.probe = pm8916_bms_vm_battery_probe,
+	.suspend = pm8916_bms_vm_battery_suspend,
+	.resume = pm8916_bms_vm_battery_resume,
+};
+module_platform_driver(pm8916_bms_vm_battery_driver);
+
+MODULE_DESCRIPTION("pm8916 BMS-VM driver");
+MODULE_AUTHOR("Nikita Travkin <[e-mail]>");
+MODULE_LICENSE("GPL");