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Message-ID: <20220917141736.200f6de2@jic23-huawei>
Date: Sat, 17 Sep 2022 14:17:36 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: Angel Iglesias <ang.iglesiasg@...il.com>
Cc: linux-iio <linux-iio@...r.kernel.org>,
Lars-Peter Clausen <lars@...afoo.de>,
Paul Cercueil <paul@...pouillou.net>,
"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
Ulf Hansson <ulf.hansson@...aro.org>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 5/9] iio: pressure: bmp280: Fix alignment for DMA
safety
On Tue, 13 Sep 2022 01:48:21 +0200
Angel Iglesias <ang.iglesiasg@...il.com> wrote:
> Adds DMA-safe buffers to driver data struct to store raw data from sensors
>
> The multiple buffers used thorough the driver share the same memory
> allocated as part of the device data instance. The union containing
> the buffers is aligned to allow safe usage with DMA operations, such
> as regmap bulk read calls.
>
> Updated measurement and calibration reading functions to use the safe
> DMA buffers.
>
> Suggested-by: Jonathan Cameron <jic23@...nel.org>
> Signed-off-by: Angel Iglesias <ang.iglesiasg@...il.com>
Applied
> ---
> drivers/iio/pressure/bmp280-core.c | 131 ++++++++++++++++-------------
> drivers/iio/pressure/bmp280.h | 4 +-
> 2 files changed, 76 insertions(+), 59 deletions(-)
>
> diff --git a/drivers/iio/pressure/bmp280-core.c b/drivers/iio/pressure/bmp280-core.c
> index 203623d32032..b6a16a580962 100644
> --- a/drivers/iio/pressure/bmp280-core.c
> +++ b/drivers/iio/pressure/bmp280-core.c
> @@ -32,6 +32,8 @@
> #include <linux/pm_runtime.h>
> #include <linux/random.h>
>
> +#include <asm/unaligned.h>
> +
> #include "bmp280.h"
>
> /*
> @@ -106,6 +108,21 @@ struct bmp280_data {
> * calculation.
> */
> s32 t_fine;
> +
> + /*
> + * DMA (thus cache coherency maintenance) may require the
> + * transfer buffers to live in their own cache lines.
> + */
> + union {
> + /* Sensor data buffer */
> + u8 buf[3];
> + /* Calibration data buffers */
> + __le16 bmp280_cal_buf[BMP280_CONTIGUOUS_CALIB_REGS / 2];
> + __be16 bmp180_cal_buf[BMP180_REG_CALIB_COUNT / 2];
> + /* Miscellaneous, endianess-aware data buffers */
> + __le16 le16;
> + __be16 be16;
> + } __aligned(IIO_DMA_MINALIGN);
> };
>
> struct bmp280_chip_info {
> @@ -160,13 +177,12 @@ static const struct iio_chan_spec bmp280_channels[] = {
> static int bmp280_read_calib(struct bmp280_data *data)
> {
> struct bmp280_calib *calib = &data->calib.bmp280;
> - __le16 c_buf[BMP280_CONTIGUOUS_CALIB_REGS / 2];
> int ret;
>
>
> /* Read temperature and pressure calibration values. */
> ret = regmap_bulk_read(data->regmap, BMP280_REG_COMP_TEMP_START,
> - c_buf, sizeof(c_buf));
> + data->bmp280_cal_buf, sizeof(data->bmp280_cal_buf));
> if (ret < 0) {
> dev_err(data->dev,
> "failed to read temperature and pressure calibration parameters\n");
> @@ -174,23 +190,23 @@ static int bmp280_read_calib(struct bmp280_data *data)
> }
>
> /* Toss the temperature and pressure calibration data into the entropy pool */
> - add_device_randomness(c_buf, sizeof(c_buf));
> + add_device_randomness(data->bmp280_cal_buf, sizeof(data->bmp280_cal_buf));
>
> /* Parse temperature calibration values. */
> - calib->T1 = le16_to_cpu(c_buf[T1]);
> - calib->T2 = le16_to_cpu(c_buf[T2]);
> - calib->T3 = le16_to_cpu(c_buf[T3]);
> + calib->T1 = le16_to_cpu(data->bmp280_cal_buf[T1]);
> + calib->T2 = le16_to_cpu(data->bmp280_cal_buf[T2]);
> + calib->T3 = le16_to_cpu(data->bmp280_cal_buf[T3]);
>
> /* Parse pressure calibration values. */
> - calib->P1 = le16_to_cpu(c_buf[P1]);
> - calib->P2 = le16_to_cpu(c_buf[P2]);
> - calib->P3 = le16_to_cpu(c_buf[P3]);
> - calib->P4 = le16_to_cpu(c_buf[P4]);
> - calib->P5 = le16_to_cpu(c_buf[P5]);
> - calib->P6 = le16_to_cpu(c_buf[P6]);
> - calib->P7 = le16_to_cpu(c_buf[P7]);
> - calib->P8 = le16_to_cpu(c_buf[P8]);
> - calib->P9 = le16_to_cpu(c_buf[P9]);
> + calib->P1 = le16_to_cpu(data->bmp280_cal_buf[P1]);
> + calib->P2 = le16_to_cpu(data->bmp280_cal_buf[P2]);
> + calib->P3 = le16_to_cpu(data->bmp280_cal_buf[P3]);
> + calib->P4 = le16_to_cpu(data->bmp280_cal_buf[P4]);
> + calib->P5 = le16_to_cpu(data->bmp280_cal_buf[P5]);
> + calib->P6 = le16_to_cpu(data->bmp280_cal_buf[P6]);
> + calib->P7 = le16_to_cpu(data->bmp280_cal_buf[P7]);
> + calib->P8 = le16_to_cpu(data->bmp280_cal_buf[P8]);
> + calib->P9 = le16_to_cpu(data->bmp280_cal_buf[P9]);
>
> return 0;
> }
> @@ -200,8 +216,6 @@ static int bme280_read_calib(struct bmp280_data *data)
> struct bmp280_calib *calib = &data->calib.bmp280;
> struct device *dev = data->dev;
> unsigned int tmp;
> - __le16 l16;
> - __be16 b16;
> int ret;
>
> /* Load shared calibration params with bmp280 first */
> @@ -226,12 +240,13 @@ static int bme280_read_calib(struct bmp280_data *data)
> }
> calib->H1 = tmp;
>
> - ret = regmap_bulk_read(data->regmap, BMP280_REG_COMP_H2, &l16, 2);
> + ret = regmap_bulk_read(data->regmap, BMP280_REG_COMP_H2,
> + &data->le16, sizeof(data->le16));
> if (ret < 0) {
> dev_err(dev, "failed to read H2 comp value\n");
> return ret;
> }
> - calib->H2 = sign_extend32(le16_to_cpu(l16), 15);
> + calib->H2 = sign_extend32(le16_to_cpu(data->le16), 15);
>
> ret = regmap_read(data->regmap, BMP280_REG_COMP_H3, &tmp);
> if (ret < 0) {
> @@ -240,20 +255,22 @@ static int bme280_read_calib(struct bmp280_data *data)
> }
> calib->H3 = tmp;
>
> - ret = regmap_bulk_read(data->regmap, BMP280_REG_COMP_H4, &b16, 2);
> + ret = regmap_bulk_read(data->regmap, BMP280_REG_COMP_H4,
> + &data->be16, sizeof(data->be16));
> if (ret < 0) {
> dev_err(dev, "failed to read H4 comp value\n");
> return ret;
> }
> - calib->H4 = sign_extend32(((be16_to_cpu(b16) >> 4) & 0xff0) |
> - (be16_to_cpu(b16) & 0xf), 11);
> + calib->H4 = sign_extend32(((be16_to_cpu(data->be16) >> 4) & 0xff0) |
> + (be16_to_cpu(data->be16) & 0xf), 11);
>
> - ret = regmap_bulk_read(data->regmap, BMP280_REG_COMP_H5, &l16, 2);
> + ret = regmap_bulk_read(data->regmap, BMP280_REG_COMP_H5,
> + &data->le16, sizeof(data->le16));
> if (ret < 0) {
> dev_err(dev, "failed to read H5 comp value\n");
> return ret;
> }
> - calib->H5 = sign_extend32(FIELD_GET(BMP280_COMP_H5_MASK, le16_to_cpu(l16)), 11);
> + calib->H5 = sign_extend32(FIELD_GET(BMP280_COMP_H5_MASK, le16_to_cpu(data->le16)), 11);
>
> ret = regmap_read(data->regmap, BMP280_REG_COMP_H6, &tmp);
> if (ret < 0) {
> @@ -348,16 +365,16 @@ static int bmp280_read_temp(struct bmp280_data *data,
> int *val)
> {
> s32 adc_temp, comp_temp;
> - __be32 tmp = 0;
> int ret;
>
> - ret = regmap_bulk_read(data->regmap, BMP280_REG_TEMP_MSB, &tmp, 3);
> + ret = regmap_bulk_read(data->regmap, BMP280_REG_TEMP_MSB,
> + data->buf, sizeof(data->buf));
> if (ret < 0) {
> dev_err(data->dev, "failed to read temperature\n");
> return ret;
> }
>
> - adc_temp = FIELD_GET(BMP280_MEAS_TRIM_MASK, be32_to_cpu(tmp));
> + adc_temp = FIELD_GET(BMP280_MEAS_TRIM_MASK, get_unaligned_be24(data->buf));
> if (adc_temp == BMP280_TEMP_SKIPPED) {
> /* reading was skipped */
> dev_err(data->dev, "reading temperature skipped\n");
> @@ -381,7 +398,6 @@ static int bmp280_read_press(struct bmp280_data *data,
> int *val, int *val2)
> {
> u32 comp_press;
> - __be32 tmp = 0;
> s32 adc_press;
> int ret;
>
> @@ -390,13 +406,14 @@ static int bmp280_read_press(struct bmp280_data *data,
> if (ret < 0)
> return ret;
>
> - ret = regmap_bulk_read(data->regmap, BMP280_REG_PRESS_MSB, &tmp, 3);
> + ret = regmap_bulk_read(data->regmap, BMP280_REG_PRESS_MSB,
> + data->buf, sizeof(data->buf));
> if (ret < 0) {
> dev_err(data->dev, "failed to read pressure\n");
> return ret;
> }
>
> - adc_press = FIELD_GET(BMP280_MEAS_TRIM_MASK, be32_to_cpu(tmp));
> + adc_press = FIELD_GET(BMP280_MEAS_TRIM_MASK, get_unaligned_be24(data->buf));
> if (adc_press == BMP280_PRESS_SKIPPED) {
> /* reading was skipped */
> dev_err(data->dev, "reading pressure skipped\n");
> @@ -414,7 +431,6 @@ static int bmp280_read_humid(struct bmp280_data *data, int *val, int *val2)
> {
> u32 comp_humidity;
> s32 adc_humidity;
> - __be16 tmp;
> int ret;
>
> /* Read and compensate temperature so we get a reading of t_fine. */
> @@ -422,13 +438,14 @@ static int bmp280_read_humid(struct bmp280_data *data, int *val, int *val2)
> if (ret < 0)
> return ret;
>
> - ret = regmap_bulk_read(data->regmap, BMP280_REG_HUMIDITY_MSB, &tmp, 2);
> + ret = regmap_bulk_read(data->regmap, BMP280_REG_HUMIDITY_MSB,
> + &data->be16, sizeof(data->be16));
> if (ret < 0) {
> dev_err(data->dev, "failed to read humidity\n");
> return ret;
> }
>
> - adc_humidity = be16_to_cpu(tmp);
> + adc_humidity = be16_to_cpu(data->be16);
> if (adc_humidity == BMP280_HUMIDITY_SKIPPED) {
> /* reading was skipped */
> dev_err(data->dev, "reading humidity skipped\n");
> @@ -769,7 +786,6 @@ static int bmp180_measure(struct bmp280_data *data, u8 ctrl_meas)
>
> static int bmp180_read_adc_temp(struct bmp280_data *data, int *val)
> {
> - __be16 tmp;
> int ret;
>
> ret = bmp180_measure(data,
> @@ -778,11 +794,12 @@ static int bmp180_read_adc_temp(struct bmp280_data *data, int *val)
> if (ret)
> return ret;
>
> - ret = regmap_bulk_read(data->regmap, BMP180_REG_OUT_MSB, &tmp, 2);
> + ret = regmap_bulk_read(data->regmap, BMP180_REG_OUT_MSB,
> + &data->be16, sizeof(data->be16));
> if (ret)
> return ret;
>
> - *val = be16_to_cpu(tmp);
> + *val = be16_to_cpu(data->be16);
>
> return 0;
> }
> @@ -790,36 +807,36 @@ static int bmp180_read_adc_temp(struct bmp280_data *data, int *val)
> static int bmp180_read_calib(struct bmp280_data *data)
> {
> struct bmp180_calib *calib = &data->calib.bmp180;
> - __be16 buf[BMP180_REG_CALIB_COUNT / 2];
> int ret;
> int i;
>
> - ret = regmap_bulk_read(data->regmap, BMP180_REG_CALIB_START, buf,
> - sizeof(buf));
> + ret = regmap_bulk_read(data->regmap, BMP180_REG_CALIB_START,
> + data->bmp180_cal_buf, sizeof(data->bmp180_cal_buf));
>
> if (ret < 0)
> return ret;
>
> /* None of the words has the value 0 or 0xFFFF */
> - for (i = 0; i < ARRAY_SIZE(buf); i++) {
> - if (buf[i] == cpu_to_be16(0) || buf[i] == cpu_to_be16(0xffff))
> + for (i = 0; i < ARRAY_SIZE(data->bmp180_cal_buf); i++) {
> + if (data->bmp180_cal_buf[i] == cpu_to_be16(0) ||
> + data->bmp180_cal_buf[i] == cpu_to_be16(0xffff))
> return -EIO;
> }
>
> /* Toss the calibration data into the entropy pool */
> - add_device_randomness(buf, sizeof(buf));
> -
> - calib->AC1 = be16_to_cpu(buf[AC1]);
> - calib->AC2 = be16_to_cpu(buf[AC2]);
> - calib->AC3 = be16_to_cpu(buf[AC3]);
> - calib->AC4 = be16_to_cpu(buf[AC4]);
> - calib->AC5 = be16_to_cpu(buf[AC5]);
> - calib->AC6 = be16_to_cpu(buf[AC6]);
> - calib->B1 = be16_to_cpu(buf[B1]);
> - calib->B2 = be16_to_cpu(buf[B2]);
> - calib->MB = be16_to_cpu(buf[MB]);
> - calib->MC = be16_to_cpu(buf[MC]);
> - calib->MD = be16_to_cpu(buf[MD]);
> + add_device_randomness(data->bmp180_cal_buf, sizeof(data->bmp180_cal_buf));
> +
> + calib->AC1 = be16_to_cpu(data->bmp180_cal_buf[AC1]);
> + calib->AC2 = be16_to_cpu(data->bmp180_cal_buf[AC2]);
> + calib->AC3 = be16_to_cpu(data->bmp180_cal_buf[AC3]);
> + calib->AC4 = be16_to_cpu(data->bmp180_cal_buf[AC4]);
> + calib->AC5 = be16_to_cpu(data->bmp180_cal_buf[AC5]);
> + calib->AC6 = be16_to_cpu(data->bmp180_cal_buf[AC6]);
> + calib->B1 = be16_to_cpu(data->bmp180_cal_buf[B1]);
> + calib->B2 = be16_to_cpu(data->bmp180_cal_buf[B2]);
> + calib->MB = be16_to_cpu(data->bmp180_cal_buf[MB]);
> + calib->MC = be16_to_cpu(data->bmp180_cal_buf[MC]);
> + calib->MD = be16_to_cpu(data->bmp180_cal_buf[MD]);
>
> return 0;
> }
> @@ -868,7 +885,6 @@ static int bmp180_read_temp(struct bmp280_data *data, int *val)
> static int bmp180_read_adc_press(struct bmp280_data *data, int *val)
> {
> u8 oss = data->oversampling_press;
> - __be32 tmp = 0;
> int ret;
>
> ret = bmp180_measure(data,
> @@ -878,11 +894,12 @@ static int bmp180_read_adc_press(struct bmp280_data *data, int *val)
> if (ret)
> return ret;
>
> - ret = regmap_bulk_read(data->regmap, BMP180_REG_OUT_MSB, &tmp, 3);
> + ret = regmap_bulk_read(data->regmap, BMP180_REG_OUT_MSB,
> + data->buf, sizeof(data->buf));
> if (ret)
> return ret;
>
> - *val = (be32_to_cpu(tmp) >> 8) >> (8 - oss);
> + *val = get_unaligned_be24(data->buf) >> (8 - oss);
>
> return 0;
> }
> diff --git a/drivers/iio/pressure/bmp280.h b/drivers/iio/pressure/bmp280.h
> index 03a539223417..c9214a7e5cc6 100644
> --- a/drivers/iio/pressure/bmp280.h
> +++ b/drivers/iio/pressure/bmp280.h
> @@ -13,8 +13,8 @@
> #define BMP280_REG_PRESS_LSB 0xF8
> #define BMP280_REG_PRESS_MSB 0xF7
>
> -/* Helper mask to truncate excess 12 bits on pressure and temp readings */
> -#define BMP280_MEAS_TRIM_MASK GENMASK(31, 12)
> +/* Helper mask to truncate excess 4 bits on pressure and temp readings */
> +#define BMP280_MEAS_TRIM_MASK GENMASK(24, 4)
>
> #define BMP280_REG_CONFIG 0xF5
> #define BMP280_REG_CTRL_MEAS 0xF4
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