iio:chemical:bme680: Fix SPI read interface

The SPI interface implementation was completely broken.

When using the SPI interface, there are only 7 address bits, the upper bit
is controlled by a page select register. The core needs access to both
ranges, so implement register read/write for both regions. The regmap
paging functionality didn't agree with a register that needs to be read
and modified, so I implemented a custom paging algorithm.

This fixes that the device wouldn't even probe in SPI mode.

The SPI interface then isn't different from I2C, merged them into the core,
and the I2C/SPI named registers are no longer needed.

Implemented register value caching for the registers to reduce the I2C/SPI
data transfers considerably.

The calibration set reads as all zeroes until some undefined point in time,
and I couldn't determine what makes it valid. The datasheet mentions these
registers but does not provide any hints on when they become valid, and they
aren't even enumerated in the memory map. So check the calibration and
retry reading it from the device after each measurement until it provides
something valid.

Despite the size this is suitable for a stable backport given that
it seems the SPI support never worked.

Signed-off-by: Mike Looijmans <mike.looijmans@topic.nl>
Fixes: 1b3bd8592780 ("iio: chemical: Add support for Bosch BME680 sensor");
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

1 files changed, 38 insertions, 0 deletions

diff --git a/drivers/iio/chemical/bme680_core.c b/drivers/iio/chemical/bme680_core.c
index fefe32b5b69d..ccde4c65ff93 100644
--- a/drivers/iio/chemical/bme680_core.c
+++ b/drivers/iio/chemical/bme680_core.c
@@ -63,9 +63,23 @@ struct bme680_data {
 	s32 t_fine;
 };
 
+static const struct regmap_range bme680_volatile_ranges[] = {
+	regmap_reg_range(BME680_REG_MEAS_STAT_0, BME680_REG_GAS_R_LSB),
+	regmap_reg_range(BME680_REG_STATUS, BME680_REG_STATUS),
+	regmap_reg_range(BME680_T2_LSB_REG, BME680_GH3_REG),
+};
+
+static const struct regmap_access_table bme680_volatile_table = {
+	.yes_ranges	= bme680_volatile_ranges,
+	.n_yes_ranges	= ARRAY_SIZE(bme680_volatile_ranges),
+};
+
 const struct regmap_config bme680_regmap_config = {
 	.reg_bits = 8,
 	.val_bits = 8,
+	.max_register = 0xef,
+	.volatile_table = &bme680_volatile_table,
+	.cache_type = REGCACHE_RBTREE,
 };
 EXPORT_SYMBOL(bme680_regmap_config);
 
@@ -316,6 +330,10 @@ static s16 bme680_compensate_temp(struct bme680_data *data,
 	s64 var1, var2, var3;
 	s16 calc_temp;
 
+	/* If the calibration is invalid, attempt to reload it */
+	if (!calib->par_t2)
+		bme680_read_calib(data, calib);
+
 	var1 = (adc_temp >> 3) - (calib->par_t1 << 1);
 	var2 = (var1 * calib->par_t2) >> 11;
 	var3 = ((var1 >> 1) * (var1 >> 1)) >> 12;
@@ -865,8 +883,28 @@ int bme680_core_probe(struct device *dev, struct regmap *regmap,
 {
 	struct iio_dev *indio_dev;
 	struct bme680_data *data;
+	unsigned int val;
 	int ret;
 
+	ret = regmap_write(regmap, BME680_REG_SOFT_RESET,
+			   BME680_CMD_SOFTRESET);
+	if (ret < 0) {
+		dev_err(dev, "Failed to reset chip\n");
+		return ret;
+	}
+
+	ret = regmap_read(regmap, BME680_REG_CHIP_ID, &val);
+	if (ret < 0) {
+		dev_err(dev, "Error reading chip ID\n");
+		return ret;
+	}
+
+	if (val != BME680_CHIP_ID_VAL) {
+		dev_err(dev, "Wrong chip ID, got %x expected %x\n",
+				val, BME680_CHIP_ID_VAL);
+		return -ENODEV;
+	}
+
 	indio_dev = devm_iio_device_alloc(dev, sizeof(*data));
 	if (!indio_dev)
 		return -ENOMEM;