[PATCH v2 6/6] iio: pressure: dps310: add Zilltek ZTS8032 support

[Paulius Zaleckas <paulius.zaleckas@gmail.com>]

The Zilltek ZTS8032 has the DPS310 register map, scale factors and
compensation, with these differences:

- two more pressure coefficients, c31 and c40 at 0x22-0x25, adding
  c40 * Praw_sc^4 + c31 * Traw_sc * Praw_sc^3 to the polynomial
- TMP_EXT is MEAS_CFG bit 3, and the temperature coefficients are for
  the internal sensor (COEF_SRCE reads 0x06). TMP_CFG bit 7 is the top
  bit of a 4-bit TMP_RATE, so the DPS310 TMP_EXT write would select a
  25/16 Hz background rate instead of the external sensor.
- product ID 0x11 instead of 0x10, the driver does not check it

Add its chip data, reading 22 coefficient bytes and leaving TMP_CFG at
0, and the I2C and OF IDs.

Tested on a ZTS8032 at 0x76 over I2C: in_pressure_input is within 1 Pa
of the datasheet formula evaluated from the raw and coefficient
registers at every oversampling rate from 1 to 128, and TMP_CFG reads
0x00 after probe.

Assisted-by: LLM
Signed-off-by: Paulius Zaleckas <paulius.zaleckas@gmail.com>
---
 drivers/iio/pressure/Kconfig  |  4 ++--
 drivers/iio/pressure/dps310.c | 26 +++++++++++++++++++++++++-
 2 files changed, 27 insertions(+), 3 deletions(-)

diff --git a/drivers/iio/pressure/Kconfig b/drivers/iio/pressure/Kconfig
index cef8b90b9ae7..e407243e131c 100644
--- a/drivers/iio/pressure/Kconfig
+++ b/drivers/iio/pressure/Kconfig
@@ -115,8 +115,8 @@ config DPS310
 	select IIO_BUFFER
 	select IIO_TRIGGERED_BUFFER
 	help
-	  Support for the Infineon DPS310 digital barometric pressure sensor.
-	  It can be accessed over I2C bus.
+	  Support for the Infineon DPS310 and Zilltek ZTS8032 digital
+	  barometric pressure sensors. They can be accessed over I2C bus.
 
 	  This driver can also be built as a module.  If so, the module will be
 	  called dps310.
diff --git a/drivers/iio/pressure/dps310.c b/drivers/iio/pressure/dps310.c
index 3b27a61b70a5..be8b0c053c4a 100644
--- a/drivers/iio/pressure/dps310.c
+++ b/drivers/iio/pressure/dps310.c
@@ -7,6 +7,10 @@
  *
  * https://www.infineon.com/dgdl/?fileId=5546d462576f34750157750826c42242
  *
+ * The Zilltek ZTS8032 is register compatible, with two more pressure
+ * calibration coefficients (c31, c40) and temperature calibrated against
+ * the internal sensor.
+ *
  * Temperature calculation:
  *   c0 * 0.5 + c1 * T_raw / kT °C
  *
@@ -62,6 +66,7 @@
 #define  DPS310_RESET_MAGIC	0x09
 #define DPS310_COEF_BASE	0x10
 #define DPS310_COEF_LEN		18
+#define ZTS8032_COEF_LEN	22
 
 /* Make sure sleep time is <= 30ms for usleep_range */
 #define DPS310_POLL_SLEEP_US(t)		min(30000, (t) / 8)
@@ -98,6 +103,13 @@ static const struct dps310_chip_info dps310_chip_info = {
 	.coef_len = DPS310_COEF_LEN,
 };
 
+/* TMP_CFG bit 7 is a rate bit here; the internal sensor is the default */
+static const struct dps310_chip_info zts8032_chip_info = {
+	.name = "zts8032",
+	.tmp_cfg = 0,
+	.coef_len = ZTS8032_COEF_LEN,
+};
+
 struct dps310_data {
 	struct i2c_client *client;
 	struct regmap *regmap;
@@ -106,6 +118,7 @@ struct dps310_data {
 
 	s32 c0, c1;
 	s32 c00, c10, c20, c30, c01, c11, c21;
+	s32 c31, c40;
 	s32 pressure_raw;
 	s32 temp_raw;
 	bool timeout_recovery_failed;
@@ -162,7 +175,7 @@ static const struct iio_chan_spec dps310_channels[] = {
 static int dps310_get_coefs(struct dps310_data *data)
 {
 	int rc;
-	u8 coef[DPS310_COEF_LEN];
+	u8 coef[ZTS8032_COEF_LEN];
 	u32 c0, c1;
 	u32 c00, c10, c20, c30, c01, c11, c21;
 
@@ -208,6 +221,11 @@ static int dps310_get_coefs(struct dps310_data *data)
 	c30 = (coef[16] << 8) | coef[17];
 	data->c30 = sign_extend32(c30, 15);
 
+	if (data->info->coef_len == ZTS8032_COEF_LEN) {
+		data->c31 = sign_extend32((coef[18] << 8) | coef[19], 15);
+		data->c40 = sign_extend32((coef[20] << 8) | coef[21], 15);
+	}
+
 	return 0;
 }
 
@@ -696,6 +714,7 @@ static int dps310_calculate_pressure(struct dps310_data *data, int *val)
 	s64 ts;
 	s64 x2;
 	s64 x3;
+	s64 x4;
 
 	rc = dps310_get_pres_k(data, &kp);
 	if (rc)
@@ -716,6 +735,7 @@ static int dps310_calculate_pressure(struct dps310_data *data, int *val)
 	ts = div_s64(t * DPS310_Q_ONE, kt);
 	x2 = dps310_mul_q(ps, ps);
 	x3 = dps310_mul_q(x2, ps);
+	x4 = dps310_mul_q(x3, ps);
 
 	pressure = data->c00 * DPS310_Q_ONE;
 	pressure += div_s64(p * data->c10 * DPS310_Q_ONE, kp);
@@ -723,6 +743,8 @@ static int dps310_calculate_pressure(struct dps310_data *data, int *val)
 	pressure += dps310_mul_q(data->c11 * ps, ts);
 	pressure += data->c20 * x2 + data->c30 * x3;
 	pressure += dps310_mul_q(data->c21 * x2, ts);
+	/* ZTS8032 only, c31 and c40 are zero on the DPS310 */
+	pressure += data->c40 * x4 + dps310_mul_q(data->c31 * x3, ts);
 	pressure >>= DPS310_Q;
 	if (pressure < 0LL)
 		return -ERANGE;
@@ -1041,12 +1063,14 @@ static int dps310_probe(struct i2c_client *client)
 
 static const struct i2c_device_id dps310_id[] = {
 	{ .name = "dps310", .driver_data = (kernel_ulong_t)&dps310_chip_info },
+	{ .name = "zts8032", .driver_data = (kernel_ulong_t)&zts8032_chip_info },
 	{ }
 };
 MODULE_DEVICE_TABLE(i2c, dps310_id);
 
 static const struct of_device_id dps310_of_match[] = {
 	{ .compatible = "infineon,dps310", .data = &dps310_chip_info },
+	{ .compatible = "zilltek,zts8032", .data = &zts8032_chip_info },
 	{ }
 };
 MODULE_DEVICE_TABLE(of, dps310_of_match);
-- 
2.55.0