Date:   Thu, 21 Jan 2021 10:02:50 +0100
From:   Mike Looijmans <mike.looijmans@...ic.nl>
To:     Jonathan Cameron <Jonathan.Cameron@...wei.com>
CC:     linux-iio@...r.kernel.org, Dan Robertson <dan@...obertson.com>,
        Gaëtan André <rvlander@...tanandre.eu>,
        Jonathan Bakker <xc-racer2@...e.ca>,
        Jonathan Cameron <jic23@...nel.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Linus Walleij <linus.walleij@...aro.org>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 2/2] iio: accel: Add support for the Bosch-Sensortec
 BMI088

Comments inlined below.


Met vriendelijke groet / kind regards,

Mike Looijmans
System Expert


TOPIC Embedded Products B.V.
Materiaalweg 4, 5681 RJ Best
The Netherlands

T: +31 (0) 499 33 69 69
E: mike.looijmans@...icproducts.com
W: www.topicproducts.com

Please consider the environment before printing this e-mail
On 20-01-2021 21:22, Jonathan Cameron wrote:
> On Tue, 19 Jan 2021 13:46:22 +0100
> Mike Looijmans <mike.looijmans@...ic.nl> wrote:
> 
>> The BMI088 is a combined module with both accelerometer and gyroscope.
>> This adds the accelerometer driver support for the SPI interface.
>> The gyroscope part is already supported by the BMG160 driver.
>>
>> Signed-off-by: Mike Looijmans <mike.looijmans@...ic.nl>
>> ---
>>
>> Changes in v6:
>> Hope you have good memory - v5 was almost a year ago now
> *laughs* fresh review so probably disagree with what I said back then on
> something :)
> 
> 
> A few really small comments inline seeing as you are respinning anyway.
> 
>> Remove superfluous *val=0
>> Make sample_frequency selection into read_avail list
>>
>> Changes in v5:
>> Add includes and forward defines in header
>> BIT(7) instead of 0x80
>> Reset already sets defaults, do not set them again
>> Remove now unused bmi088_accel_set_bw
>> Remove unused AXIS_MAX
>> Use MASK define for ODR setting
>> Explain buffer use and alignment
>> Split bmi088_accel_set_power_state into "on" and "off" parts
>> Cosmetic changes to improve readability
>>
>> Changes in v4:
>> Remove unused #include directives
>> Remove unused #defines for event and irq
>> Replace (ret < 0) with (ret) for all regmap calls
>> Consistent checking of IO errors in probe and init
>> Removed #ifdef CONFIG_PM guard
>> Use bitops for set_frequency instead of loop with shift
>> s/__s16/s16/g
>> Remove excess blank lines
>> Don't return -EAGAIN in pm_runtime
>>
>> Changes in v3:
>> Processed comments from Jonathan Cameron and Lars-Peter Clausen
>> implement runtime PM (tested by code tracing) and sleep
>> fix scale and offset factors for accel and temperature and
>> return raw values instead of pre-scaled ones
>> Use iio_device_{claim,release}_direct_mode
>> Remove unused code and structs
>> Use a cache-aligned buffer for bulk read
>> Configure and enable caching register values
>>
>> Changes in v2:
>> Remove unused typedefs and variables
>> Fix error return when iio_device_register fails
>>
>>   drivers/iio/accel/Kconfig             |  18 +
>>   drivers/iio/accel/Makefile            |   2 +
>>   drivers/iio/accel/bmi088-accel-core.c | 630 ++++++++++++++++++++++++++
>>   drivers/iio/accel/bmi088-accel-spi.c  |  85 ++++
>>   drivers/iio/accel/bmi088-accel.h      |  18 +
>>   5 files changed, 753 insertions(+)
>>   create mode 100644 drivers/iio/accel/bmi088-accel-core.c
>>   create mode 100644 drivers/iio/accel/bmi088-accel-spi.c
>>   create mode 100644 drivers/iio/accel/bmi088-accel.h
>>
>> diff --git a/drivers/iio/accel/Kconfig b/drivers/iio/accel/Kconfig
>> index 2e0c62c39155..cceda3cecbcf 100644
>> --- a/drivers/iio/accel/Kconfig
>> +++ b/drivers/iio/accel/Kconfig
>> @@ -157,6 +157,24 @@ config BMC150_ACCEL_SPI
>>   	tristate
>>   	select REGMAP_SPI
>>   
>> +config BMI088_ACCEL
>> +	tristate "Bosch BMI088 Accelerometer Driver"
>> +	depends on SPI
>> +	select IIO_BUFFER
>> +	select IIO_TRIGGERED_BUFFER
>> +	select REGMAP
>> +	select BMI088_ACCEL_SPI
>> +	help
>> +	  Say yes here to build support for the Bosch BMI088 accelerometer.
>> +
>> +	  This is a combo module with both accelerometer and gyroscope. This
>> +	  driver only implements the accelerometer part, which has its own
>> +	  address and register map. BMG160 provides the gyroscope driver.
>> +
>> +config BMI088_ACCEL_SPI
>> +	tristate
>> +	select REGMAP_SPI
>> +
>>   config DA280
>>   	tristate "MiraMEMS DA280 3-axis 14-bit digital accelerometer driver"
>>   	depends on I2C
>> diff --git a/drivers/iio/accel/Makefile b/drivers/iio/accel/Makefile
>> index 4f6c1ebe13b0..32cd1342a31a 100644
>> --- a/drivers/iio/accel/Makefile
>> +++ b/drivers/iio/accel/Makefile
>> @@ -20,6 +20,8 @@ obj-$(CONFIG_BMA400_SPI) += bma400_spi.o
>>   obj-$(CONFIG_BMC150_ACCEL) += bmc150-accel-core.o
>>   obj-$(CONFIG_BMC150_ACCEL_I2C) += bmc150-accel-i2c.o
>>   obj-$(CONFIG_BMC150_ACCEL_SPI) += bmc150-accel-spi.o
>> +obj-$(CONFIG_BMI088_ACCEL) += bmi088-accel-core.o
>> +obj-$(CONFIG_BMI088_ACCEL_SPI) += bmi088-accel-spi.o
>>   obj-$(CONFIG_DA280)	+= da280.o
>>   obj-$(CONFIG_DA311)	+= da311.o
>>   obj-$(CONFIG_DMARD06)	+= dmard06.o
>> diff --git a/drivers/iio/accel/bmi088-accel-core.c b/drivers/iio/accel/bmi088-accel-core.c
>> new file mode 100644
>> index 000000000000..788e54ed0728
>> --- /dev/null
>> +++ b/drivers/iio/accel/bmi088-accel-core.c
>> @@ -0,0 +1,630 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * 3-axis accelerometer driver supporting following Bosch-Sensortec chips:
>> + *  - BMI088
>> + *
>> + * Copyright (c) 2018-2020, Topic Embedded Products
>> + */
>> +
>> +#include <linux/module.h>
>> +#include <linux/interrupt.h>
>> +#include <linux/delay.h>
> As below. Alphabetical ordering preferred.

Will do.

> 
>> +#include <linux/slab.h>
>> +#include <linux/acpi.h>
>> +#include <linux/pm.h>
>> +#include <linux/pm_runtime.h>
>> +#include <linux/iio/iio.h>
>> +#include <linux/iio/sysfs.h>
>> +#include <linux/regmap.h>
>> +#include <asm/unaligned.h>
>> +
>> +#include "bmi088-accel.h"
> ...
> 
>> +static int bmi088_accel_chip_init(struct bmi088_accel_data *data)
>> +{
>> +	struct device *dev = regmap_get_device(data->regmap);
>> +	int ret, i;
>> +	unsigned int val;
>> +
>> +	/* Do a dummy read to enable SPI interface, won't harm I2C */
>> +	regmap_read(data->regmap, BMI088_ACCEL_REG_INT_STATUS, &val);
>> +
>> +	/*
>> +	 * Reset chip to get it in a known good state. A delay of 1ms after
>> +	 * reset is required according to the data sheet
>> +	 */
>> +	ret = regmap_write(data->regmap, BMI088_ACCEL_REG_RESET,
>> +			   BMI088_ACCEL_RESET_VAL);
>> +	if (ret)
>> +		return ret;
>> +
>> +	usleep_range(1000, 2000);
>> +
>> +	/* Do a dummy read again after a reset to enable the SPI interface */
>> +	regmap_read(data->regmap, BMI088_ACCEL_REG_INT_STATUS, &val);
>> +
>> +	/* Read chip ID */
>> +	ret = regmap_read(data->regmap, BMI088_ACCEL_REG_CHIP_ID, &val);
>> +	if (ret) {
>> +		dev_err(dev, "Error: Reading chip id\n");
>> +		return ret;
>> +	}
>> +
>> +	/* Validate chip ID */
>> +	for (i = 0; i < ARRAY_SIZE(bmi088_accel_chip_info_tbl); i++) {
>> +		if (bmi088_accel_chip_info_tbl[i].chip_id == val) {
>> +			data->chip_info = &bmi088_accel_chip_info_tbl[i];
>> +			break;
>> +		}
>> +	}
>> +	if (i == ARRAY_SIZE(bmi088_accel_chip_info_tbl)) {
>> +		dev_err(dev, "Invalid chip %x\n", val);
>> +		return -ENODEV;
>> +	}
>> +
>> +	/* Enable accelerometer after reset */
>> +	return bmi088_accel_enable(data, true);
> 
> We bring the device up here, but I'm not seeing it turned off again
> in either error paths of probe or remove.
> Am I missing it somewhere?

Nah makes sense to put it back in the disabled state at removal.
I'll re-use the "suspend" code in the "remove" call so it'll be less code in 
total and things will be symetric.

> 
>> +}
>> +
>> +int bmi088_accel_core_probe(struct device *dev, struct regmap *regmap,
>> +	int irq, const char *name, bool block_supported)
>> +{
>> +	struct bmi088_accel_data *data;
>> +	struct iio_dev *indio_dev;
>> +	int ret;
>> +
>> +	indio_dev = devm_iio_device_alloc(dev, sizeof(*data));
>> +	if (!indio_dev)
>> +		return -ENOMEM;
>> +
>> +	data = iio_priv(indio_dev);
>> +	dev_set_drvdata(dev, indio_dev);
>> +
>> +	data->regmap = regmap;
>> +
>> +	ret = bmi088_accel_chip_init(data);
>> +	if (ret)
>> +		return ret;
>> +
>> +	mutex_init(&data->mutex);
>> +
>> +	indio_dev->dev.parent = dev;
>> +	indio_dev->channels = data->chip_info->channels;
>> +	indio_dev->num_channels = data->chip_info->num_channels;
>> +	indio_dev->name = name ? name : data->chip_info->name;
>> +	indio_dev->available_scan_masks = bmi088_accel_scan_masks;
>> +	indio_dev->modes = INDIO_DIRECT_MODE;
>> +	indio_dev->info = &bmi088_accel_info;
>> +
>> +	ret = pm_runtime_set_active(dev);
>> +	if (ret)
>> +		return ret;
>> +
>> +	pm_runtime_enable(dev);
>> +	pm_runtime_set_autosuspend_delay(dev, BMI088_AUTO_SUSPEND_DELAY_MS);
>> +	pm_runtime_use_autosuspend(dev);
>> +
>> +	ret = iio_device_register(indio_dev);
>> +	if (ret)
>> +		dev_err(dev, "Unable to register iio device\n");
>> +
>> +	return ret;
>> +}
>> +EXPORT_SYMBOL_GPL(bmi088_accel_core_probe);
>> +
>> +int bmi088_accel_core_remove(struct device *dev)
>> +{
>> +	struct iio_dev *indio_dev = dev_get_drvdata(dev);
>> +	struct bmi088_accel_data *data = iio_priv(indio_dev);
>> +
>> +	iio_device_unregister(indio_dev);
>> +
>> +	pm_runtime_disable(dev);
>> +	pm_runtime_set_suspended(dev);
>> +	pm_runtime_put_noidle(dev);
>> +
>> +	mutex_lock(&data->mutex);
>> +	bmi088_accel_set_mode(data, BMI088_ACCEL_MODE_SUSPEND);
>> +	mutex_unlock(&data->mutex);
>> +
>> +	return 0;
>> +}
>> +EXPORT_SYMBOL_GPL(bmi088_accel_core_remove);
>> +
>> +/* When going into system sleep, put the chip in power down */
>> +static int __maybe_unused bmi088_accel_suspend(struct device *dev)
>> +{
>> +	struct iio_dev *indio_dev = dev_get_drvdata(dev);
>> +	struct bmi088_accel_data *data = iio_priv(indio_dev);
>> +
>> +	mutex_lock(&data->mutex);
>> +	bmi088_accel_set_mode(data, BMI088_ACCEL_MODE_SUSPEND);
>> +	bmi088_accel_enable(data, false);
>> +	mutex_unlock(&data->mutex);
>> +
>> +	return 0;
>> +}
>> +
>> +static int __maybe_unused bmi088_accel_resume(struct device *dev)
>> +{
>> +	struct iio_dev *indio_dev = dev_get_drvdata(dev);
>> +	struct bmi088_accel_data *data = iio_priv(indio_dev);
>> +
>> +	mutex_lock(&data->mutex);
>> +	bmi088_accel_enable(data, true);
>> +	bmi088_accel_set_mode(data, BMI088_ACCEL_MODE_ACTIVE);
>> +	mutex_unlock(&data->mutex);
>> +
>> +	return 0;
>> +}
>> +
>> +/* For runtime PM put the chip in suspend mode */
>> +static int __maybe_unused bmi088_accel_runtime_suspend(struct device *dev)
>> +{
>> +	struct iio_dev *indio_dev = dev_get_drvdata(dev);
>> +	struct bmi088_accel_data *data = iio_priv(indio_dev);
>> +
>> +	return bmi088_accel_set_mode(data, BMI088_ACCEL_MODE_SUSPEND);
>> +}
>> +
>> +static int __maybe_unused bmi088_accel_runtime_resume(struct device *dev)
>> +{
>> +	struct iio_dev *indio_dev = dev_get_drvdata(dev);
>> +	struct bmi088_accel_data *data = iio_priv(indio_dev);
>> +	int ret;
>> +
>> +	ret = bmi088_accel_set_mode(data, BMI088_ACCEL_MODE_ACTIVE);
>> +	if (ret)
>> +		return ret;
>> +
>> +	usleep_range(BMI088_ACCEL_MAX_STARTUP_TIME_US,
>> +		     BMI088_ACCEL_MAX_STARTUP_TIME_US * 2);
>> +
>> +	return 0;
>> +}
>> +
>> +const struct dev_pm_ops bmi088_accel_pm_ops = {
>> +	SET_SYSTEM_SLEEP_PM_OPS(bmi088_accel_suspend, bmi088_accel_resume)
>> +	SET_RUNTIME_PM_OPS(bmi088_accel_runtime_suspend,
>> +			   bmi088_accel_runtime_resume, NULL)
>> +};
>> +EXPORT_SYMBOL_GPL(bmi088_accel_pm_ops);
>> +
>> +MODULE_AUTHOR("Niek van Agt <niek.van.agt@...icproducts.com>");
>> +MODULE_LICENSE("GPL v2");
>> +MODULE_DESCRIPTION("BMI088 accelerometer driver (core)");
>> diff --git a/drivers/iio/accel/bmi088-accel-spi.c b/drivers/iio/accel/bmi088-accel-spi.c
>> new file mode 100644
>> index 000000000000..7794090b8e6d
>> --- /dev/null
>> +++ b/drivers/iio/accel/bmi088-accel-spi.c
>> @@ -0,0 +1,85 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * 3-axis accelerometer driver supporting following Bosch-Sensortec chips:
>> + *  - BMI088
>> + *
>> + * Copyright (c) 2018-2020, Topic Embedded Products
>> + */
>> +
>> +#include <linux/module.h>
>> +#include <linux/slab.h>
>> +#include <linux/spi/spi.h>
>> +#include <linux/regmap.h>
> 
> If no other reason for ordering ever so slight preference for
> alphabetical order.

Will do

> 
>> +
>> +#include "bmi088-accel.h"
>> +
>> +int bmi088_regmap_spi_write(void *context, const void *data, size_t count)

This should have been a static (as reported by build bot)

>> +{
>> +	struct spi_device *spi = context;
>> +
>> +	/* Write register is same as generic SPI */
>> +	return spi_write(spi, data, count);
>> +}
>> +
>> +int bmi088_regmap_spi_read(void *context, const void *reg,
>> +				size_t reg_size, void *val, size_t val_size)
>> +{
>> +	struct spi_device *spi = context;
>> +	u8 addr[2];
>> +
>> +	addr[0] = *(u8 *)reg;
>> +	addr[0] |= BIT(7); /* Set RW = '1' */
>> +	addr[1] = 0; /* Read requires a dummy byte transfer */
>> +
>> +	return spi_write_then_read(spi, addr, sizeof(addr), val, val_size);
>> +}
>> +
>> +static struct regmap_bus bmi088_regmap_bus = {
>> +	.write = bmi088_regmap_spi_write,
>> +	.read = bmi088_regmap_spi_read,
>> +	.reg_format_endian_default = REGMAP_ENDIAN_BIG,
>> +	.val_format_endian_default = REGMAP_ENDIAN_BIG,
> 
> Aren't these both 8 bits, making endian rather irrelevant?

Indeed, all registers are accessed as 8-bit only. Where bulk-read is involved, 
the byte order in interpreted in code.

> 
>> +};
> ...
> 

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