[PATCH v3 5/5] 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, a Horner step for each of c40 and c31, and the I2C and OF IDs.

Tested on a ZTS8032 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  |  6 ++++--
 drivers/iio/pressure/dps310.c | 33 ++++++++++++++++++++++++++++++---
 2 files changed, 34 insertions(+), 5 deletions(-)

diff --git a/drivers/iio/pressure/Kconfig b/drivers/iio/pressure/Kconfig
index cef8b90b9ae7..21363d542c38 100644
--- a/drivers/iio/pressure/Kconfig
+++ b/drivers/iio/pressure/Kconfig
@@ -115,8 +115,10 @@ 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 following digital barometric pressure sensors:
+	  - Infineon DPS310
+	  - Zilltek ZTS8032
+	  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 ad3860d11592..940bde38e8e3 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
  *
@@ -63,7 +67,8 @@
 #define  DPS310_RESET_MAGIC	0x09
 #define DPS310_COEF_BASE	0x10
 #define DPS310_COEF_LEN		18
-#define DPS310_MAX_COEF_LEN	18
+#define ZTS8032_COEF_LEN	22
+#define DPS310_MAX_COEF_LEN	22
 
 /* Make sure sleep time is <= 30ms for usleep_range */
 #define DPS310_POLL_SLEEP_US(t)		min(30000, (t) / 8)
@@ -92,6 +97,7 @@ struct dps310_chip_info {
 	const char *name;
 	u8 tmp_cfg;	/* TMP_CFG at startup: sensor the coefficients are for */
 	u8 coef_len;
+	bool has_c31_c40;
 };
 
 static const struct dps310_chip_info dps310_chip_info = {
@@ -100,6 +106,14 @@ 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,
+	.has_c31_c40 = true,
+};
+
 struct dps310_data {
 	struct i2c_client *client;
 	struct regmap *regmap;
@@ -108,6 +122,7 @@ 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;
@@ -210,6 +225,11 @@ static int dps310_get_coefs(struct dps310_data *data)
 	c30 = (coef[16] << 8) | coef[17];
 	data->c30 = sign_extend32(c30, 15);
 
+	if (data->info->has_c31_c40) {
+		data->c31 = sign_extend32((coef[18] << 8) | coef[19], 15);
+		data->c40 = sign_extend32((coef[20] << 8) | coef[21], 15);
+	}
+
 	return 0;
 }
 
@@ -711,10 +731,15 @@ static int dps310_calculate_pressure(struct dps310_data *data, int *val)
 	if (rc)
 		return rc;
 
-	/* Section 4.9.1 of the DPS310 spec, Horner form to avoid overflow */
-	if (!dps310_horner_step(&prs, data->c30, p, kp) ||
+	/*
+	 * Section 4.9.1 of the DPS310 spec, Horner form to avoid overflow.
+	 * c40 and c31 are ZTS8032 only and zero on the DPS310.
+	 */
+	if (!dps310_horner_step(&prs, data->c40, p, kp) ||
+	    !dps310_horner_step(&prs, data->c30, p, kp) ||
 	    !dps310_horner_step(&prs, data->c20, p, kp) ||
 	    !dps310_horner_step(&prs, data->c10, p, kp) ||
+	    !dps310_horner_step(&tmp, data->c31, p, kp) ||
 	    !dps310_horner_step(&tmp, data->c21, p, kp) ||
 	    !dps310_horner_step(&tmp, data->c11, p, kp) ||
 	    !dps310_horner_step(&tmp, data->c01, t, kt))
@@ -1038,12 +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