[PATCH v7] power: supply: bq27xxx: detect bq27541 behind bq27411 compatible

[Rinat Muhamedgaliev via B4 Relay <devnull+rinat.muhamedgaliev.gmail.com@kernel.org>]

From: Rinat Muhamedgaliev <rinat.muhamedgaliev@gmail.com>

OnePlus 6 and 6T replacement battery packs may contain either a bq27411
or a bq27541 fuel gauge at I2C address 0x55. The device tree currently
identifies the gauge as bq27411, but a bq27541 uses a different register
map and then reports invalid battery values.

Read the DeviceType control subcommand when probing a bq27411. Keep the
existing profile for DeviceType 0x0421, but select the bq27541 profile
for DeviceType 0x0541. This retains the established DT ABI and supports
replacement packs without introducing a generic compatible.

Tested on OnePlus 6T (fajita) with DeviceType 0x0541: voltage, state of
charge, and temperature were reported correctly. Testing on hardware with
DeviceType 0x0421 would be appreciated.

Signed-off-by: Rinat Muhamedgaliev <rinat.muhamedgaliev@gmail.com>
---
 drivers/power/supply/bq27xxx_battery_i2c.c | 67 ++++++++++++++++++++++++++++++
 1 file changed, 67 insertions(+)

diff --git a/drivers/power/supply/bq27xxx_battery_i2c.c b/drivers/power/supply/bq27xxx_battery_i2c.c
index 94b00bb89c17..a9982953e4f2 100644
--- a/drivers/power/supply/bq27xxx_battery_i2c.c
+++ b/drivers/power/supply/bq27xxx_battery_i2c.c
@@ -16,6 +16,11 @@
 static DEFINE_IDR(battery_id);
 static DEFINE_MUTEX(battery_mutex);
 
+#define BQ27XXX_REG_CTRL		0x00
+#define BQ27XXX_DEVICE_TYPE		0x0001
+#define BQ27411_DEVICE_TYPE		0x0421
+#define BQ27541_DEVICE_TYPE		0x0541
+
 static irqreturn_t bq27xxx_battery_irq_handler_thread(int irq, void *data)
 {
 	struct bq27xxx_device_info *di = data;
@@ -136,6 +141,56 @@ static int bq27xxx_battery_i2c_bulk_write(struct bq27xxx_device_info *di,
 	return 0;
 }
 
+static int bq27xxx_battery_i2c_check_device_type(struct bq27xxx_device_info *di)
+{
+	enum bq27xxx_chip detected_chip;
+	int expected_type;
+	int ret;
+
+	switch (di->chip) {
+	case BQ27411:
+		expected_type = BQ27411_DEVICE_TYPE;
+		break;
+	case BQ27541:
+		expected_type = BQ27541_DEVICE_TYPE;
+		break;
+	default:
+		dev_warn(di->dev, "expected DeviceType undefined\n");
+		return 0;
+	}
+
+	ret = di->bus.write(di, BQ27XXX_REG_CTRL, BQ27XXX_DEVICE_TYPE,
+			    false);
+	if (ret < 0)
+		return ret;
+
+	ret = di->bus.read(di, BQ27XXX_REG_CTRL, false);
+	if (ret < 0)
+		return ret;
+
+	switch (ret) {
+	case BQ27411_DEVICE_TYPE:
+		detected_chip = BQ27411;
+		break;
+	case BQ27541_DEVICE_TYPE:
+		detected_chip = BQ27541;
+		break;
+	default:
+		dev_err(di->dev, "unrecognized DeviceType 0x%04x\n", ret);
+		return -ENODEV;
+	}
+
+	if (detected_chip == di->chip)
+		return 0;
+
+	dev_warn(di->dev,
+		 "detected DeviceType 0x%04x instead of expected 0x%04x\n",
+		 ret, expected_type);
+	di->chip = detected_chip;
+
+	return 0;
+}
+
 static int bq27xxx_battery_i2c_probe(struct i2c_client *client,
 				     const struct i2c_device_id *id)
 {
@@ -169,6 +224,18 @@ static int bq27xxx_battery_i2c_probe(struct i2c_client *client,
 	di->bus.read_bulk = bq27xxx_battery_i2c_bulk_read;
 	di->bus.write_bulk = bq27xxx_battery_i2c_bulk_write;
 
+	/* Add fuel gauges with supported DeviceType reporting to this list. */
+	switch (di->chip) {
+	case BQ27411:
+	case BQ27541:
+		ret = bq27xxx_battery_i2c_check_device_type(di);
+		if (ret)
+			goto err_failed;
+		break;
+	default:
+		break;
+	}
+
 	ret = bq27xxx_battery_setup(di);
 	if (ret)
 		goto err_failed;

-- 
2.56.0