This is a note to let you know that I've just added the patch titled
iio: chemical: bme680: Fix sensor data read operation
to my char-misc git tree which can be found at git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git in the char-misc-linus branch.
The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)
The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.
If you have any questions about this process, please let me know.
From 4241665e6ea063a9c1d734de790121a71db763fc Mon Sep 17 00:00:00 2001 From: Vasileios Amoiridis vassilisamir@gmail.com Date: Thu, 6 Jun 2024 23:22:56 +0200 Subject: iio: chemical: bme680: Fix sensor data read operation
A read operation is happening as follows:
a) Set sensor to forced mode b) Sensor measures values and update data registers and sleeps again c) Read data registers
In the current implementation the read operation happens immediately after the sensor is set to forced mode so the sensor does not have the time to update properly the registers. This leads to the following 2 problems:
1) The first ever value which is read by the register is always wrong 2) Every read operation, puts the register into forced mode and reads the data that were calculated in the previous conversion.
This behaviour was tested in 2 ways:
1) The internal meas_status_0 register was read before and after every read operation in order to verify that the data were ready even before the register was set to forced mode and also to check that after the forced mode was set the new data were not yet ready.
2) Physically changing the temperature and measuring the temperature
This commit adds the waiting time in between the set of the forced mode and the read of the data. The function is taken from the Bosch BME68x Sensor API [1].
[1]: https://github.com/boschsensortec/BME68x_SensorAPI/blob/v4.4.8/bme68x.c#L490
Fixes: 1b3bd8592780 ("iio: chemical: Add support for Bosch BME680 sensor") Signed-off-by: Vasileios Amoiridis vassilisamir@gmail.com Link: https://lore.kernel.org/r/20240606212313.207550-5-vassilisamir@gmail.com Cc: Stable@vger.kernel.org Signed-off-by: Jonathan Cameron Jonathan.Cameron@huawei.com --- drivers/iio/chemical/bme680.h | 2 ++ drivers/iio/chemical/bme680_core.c | 46 ++++++++++++++++++++++++++++++ 2 files changed, 48 insertions(+)
diff --git a/drivers/iio/chemical/bme680.h b/drivers/iio/chemical/bme680.h index 4edc5d21cb9f..f959252a4fe6 100644 --- a/drivers/iio/chemical/bme680.h +++ b/drivers/iio/chemical/bme680.h @@ -54,7 +54,9 @@ #define BME680_NB_CONV_MASK GENMASK(3, 0)
#define BME680_REG_MEAS_STAT_0 0x1D +#define BME680_NEW_DATA_BIT BIT(7) #define BME680_GAS_MEAS_BIT BIT(6) +#define BME680_MEAS_BIT BIT(5)
/* Calibration Parameters */ #define BME680_T2_LSB_REG 0x8A diff --git a/drivers/iio/chemical/bme680_core.c b/drivers/iio/chemical/bme680_core.c index 5db48f6d646c..500f56834b01 100644 --- a/drivers/iio/chemical/bme680_core.c +++ b/drivers/iio/chemical/bme680_core.c @@ -10,6 +10,7 @@ */ #include <linux/acpi.h> #include <linux/bitfield.h> +#include <linux/delay.h> #include <linux/device.h> #include <linux/module.h> #include <linux/log2.h> @@ -532,6 +533,43 @@ static u8 bme680_oversampling_to_reg(u8 val) return ilog2(val) + 1; }
+/* + * Taken from Bosch BME680 API: + * https://github.com/boschsensortec/BME68x_SensorAPI/blob/v4.4.8/bme68x.c#L490 + */ +static int bme680_wait_for_eoc(struct bme680_data *data) +{ + struct device *dev = regmap_get_device(data->regmap); + unsigned int check; + int ret; + /* + * (Sum of oversampling ratios * time per oversampling) + + * TPH measurement + gas measurement + wait transition from forced mode + * + heater duration + */ + int wait_eoc_us = ((data->oversampling_temp + data->oversampling_press + + data->oversampling_humid) * 1936) + (477 * 4) + + (477 * 5) + 1000 + (data->heater_dur * 1000); + + usleep_range(wait_eoc_us, wait_eoc_us + 100); + + ret = regmap_read(data->regmap, BME680_REG_MEAS_STAT_0, &check); + if (ret) { + dev_err(dev, "failed to read measurement status register.\n"); + return ret; + } + if (check & BME680_MEAS_BIT) { + dev_err(dev, "Device measurement cycle incomplete.\n"); + return -EBUSY; + } + if (!(check & BME680_NEW_DATA_BIT)) { + dev_err(dev, "No new data available from the device.\n"); + return -ENODATA; + } + + return 0; +} + static int bme680_chip_config(struct bme680_data *data) { struct device *dev = regmap_get_device(data->regmap); @@ -622,6 +660,10 @@ static int bme680_read_temp(struct bme680_data *data, int *val) if (ret < 0) return ret;
+ ret = bme680_wait_for_eoc(data); + if (ret) + return ret; + ret = regmap_bulk_read(data->regmap, BME680_REG_TEMP_MSB, &tmp, 3); if (ret < 0) { @@ -738,6 +780,10 @@ static int bme680_read_gas(struct bme680_data *data, if (ret < 0) return ret;
+ ret = bme680_wait_for_eoc(data); + if (ret) + return ret; + ret = regmap_read(data->regmap, BME680_REG_MEAS_STAT_0, &check); if (check & BME680_GAS_MEAS_BIT) { dev_err(dev, "gas measurement incomplete\n");