Re: [PATCH 4/5] iio: imu: Add support for adis16475

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On 3/5/20 10:58 AM, Sa, Nuno wrote:
On Wed, 2020-03-04 at 17:59 +0000, Sa, Nuno wrote:
[External]

On Tue, 2020-03-03 at 21:08 +0000, Jonathan Cameron wrote:
[External]

On Tue, 25 Feb 2020 13:41:51 +0100
Nuno Sá <nuno.sa@xxxxxxxxxx> wrote:

Support ADIS16475 and similar IMU devices. These devices are
a precision, miniature MEMS inertial measurement unit (IMU) that
includes a triaxial gyroscope and a triaxial accelerometer. Each
inertial sensor combines with signal conditioning that optimizes
dynamic performance.

The driver adds support for the following devices:
  * adis16470, adis16475, adis16477, adis16465, adis16467,
adis16500,
    adis16505, adis16507.

Signed-off-by: Nuno Sá <nuno.sa@xxxxxxxxxx>
A few bits and pieces inline.

Thanks,

Jonathan


---
  .../ABI/testing/sysfs-bus-iio-imu-adis16475   |    7 +
  MAINTAINERS                                   |    8 +
  drivers/iio/imu/Kconfig                       |   13 +
  drivers/iio/imu/Makefile                      |    1 +
  drivers/iio/imu/adis16475.c                   | 1304
+++++++++++++++++
  5 files changed, 1333 insertions(+)
  create mode 100644 Documentation/ABI/testing/sysfs-bus-iio-imu-
adis16475
  create mode 100644 drivers/iio/imu/adis16475.c

diff --git a/Documentation/ABI/testing/sysfs-bus-iio-imu-
adis16475
b/Documentation/ABI/testing/sysfs-bus-iio-imu-adis16475
new file mode 100644
index 000000000000..e2c3776035ea
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-bus-iio-imu-adis16475
@@ -0,0 +1,7 @@
+What:		/sys/bus/iio/devices/iio:deviceX/burst_mode_ena
ble
+KernelVersion:
+Contact:	linux-iio@xxxxxxxxxxxxxxx
+Description:
+		Use the device burst read mode when reading buffered
+		data. This mode provides a way to read a batch of
+		output data registers, using a continuous stream of
bits.
See comment on this below.  I'm not keen on this being exposed to
userspace
because it will rarely have any idea how to set it.

diff --git a/MAINTAINERS b/MAINTAINERS
index 8fa40c3eb72a..f11262f1f3bb 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1008,6 +1008,14 @@ W:	
http://ez.analog.com/community/linux-device-drivers
  F:	drivers/iio/imu/adis16460.c
  F:	Documentation/devicetree/bindings/iio/imu/adi,adis16460
.yaml
+ANALOG DEVICES INC ADIS16475 DRIVER
+M:	Nuno Sa <nuno.sa@xxxxxxxxxx>
+L:	linux-iio@xxxxxxxxxxxxxxx
+W:	http://ez.analog.com/community/linux-device-drivers
+S:	Supported
+F:	drivers/iio/imu/adis16475.c
+F:	Documentation/ABI/testing/sysfs-bus-iio-imu-adis16475
+
  ANALOG DEVICES INC ADM1177 DRIVER
  M:	Beniamin Bia <beniamin.bia@xxxxxxxxxx>
  M:	Michael Hennerich <Michael.Hennerich@xxxxxxxxxx>
diff --git a/drivers/iio/imu/Kconfig b/drivers/iio/imu/Kconfig
index 60bb1029e759..fc4123d518bc 100644
--- a/drivers/iio/imu/Kconfig
+++ b/drivers/iio/imu/Kconfig
@@ -29,6 +29,19 @@ config ADIS16460
  	  To compile this driver as a module, choose M here: the module
will be
  	  called adis16460.
+config ADIS16475
+	tristate "Analog Devices ADIS16475 and similar IMU driver"
+	depends on SPI
+	select IIO_ADIS_LIB
+	select IIO_ADIS_LIB_BUFFER if IIO_BUFFER
+	help
+	  Say yes here to build support for Analog Devices ADIS16470,
ADIS16475,
+	  ADIS16477, ADIS16465, ADIS16467, ADIS16500, ADIS16505,
ADIS16507 inertial
+	  sensors.
+
+	  To compile this driver as a module, choose M here: the module
will be
+	  called adis16475.
+
  config ADIS16480
  	tristate "Analog Devices ADIS16480 and similar IMU driver"
  	depends on SPI
diff --git a/drivers/iio/imu/Makefile b/drivers/iio/imu/Makefile
index 5237fd4bc384..88b2c4555230 100644
--- a/drivers/iio/imu/Makefile
+++ b/drivers/iio/imu/Makefile
@@ -6,6 +6,7 @@
  # When adding new entries keep the list in alphabetical order
  obj-$(CONFIG_ADIS16400) += adis16400.o
  obj-$(CONFIG_ADIS16460) += adis16460.o
+obj-$(CONFIG_ADIS16475) += adis16475.o
  obj-$(CONFIG_ADIS16480) += adis16480.o
adis_lib-y += adis.o
diff --git a/drivers/iio/imu/adis16475.c
b/drivers/iio/imu/adis16475.c
new file mode 100644
index 000000000000..f7c637734ec8
--- /dev/null
+++ b/drivers/iio/imu/adis16475.c
@@ -0,0 +1,1304 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * ADIS16475 IMU driver
+ *
+ * Copyright 2019 Analog Devices Inc.
+ */
+#include <asm/unaligned.h>
+#include <linux/bitfield.h>
+#include <linux/bitops.h>
+#include <linux/clk.h>
+#include <linux/debugfs.h>
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/kernel.h>
+#include <linux/iio/buffer.h>
+#include <linux/iio/iio.h>
+#include <linux/iio/imu/adis.h>
+#include <linux/iio/sysfs.h>
+#include <linux/iio/trigger_consumer.h>
+#include <linux/irq.h>
+#include <linux/module.h>
+#include <linux/spi/spi.h>
+
+#define ADIS16475_REG_DIAG_STAT		0x02
+#define ADIS16475_REG_X_GYRO_L		0x04
+#define ADIS16475_REG_Y_GYRO_L		0x08
+#define ADIS16475_REG_Z_GYRO_L		0x0C
+#define ADIS16475_REG_X_ACCEL_L		0x10
+#define ADIS16475_REG_Y_ACCEL_L		0x14
+#define ADIS16475_REG_Z_ACCEL_L		0x18
+#define ADIS16475_REG_TEMP_OUT		0x1c
+#define ADIS16475_REG_X_GYRO_BIAS_L	0x40
+#define ADIS16475_REG_Y_GYRO_BIAS_L	0x44
+#define ADIS16475_REG_Z_GYRO_BIAS_L	0x48
+#define ADIS16475_REG_X_ACCEL_BIAS_L	0x4c
+#define ADIS16475_REG_Y_ACCEL_BIAS_L	0x50
+#define ADIS16475_REG_Z_ACCEL_BIAS_L	0x54
+#define ADIS16475_REG_FILT_CTRL		0x5c
+#define ADIS16475_FILT_CTRL_MASK	GENMASK(2, 0)
+#define ADIS16475_FILT_CTRL(x)		FIELD_PREP(ADIS16475_FI
LT_CTRL_MASK, x)
+#define ADIS16475_REG_MSG_CTRL		0x60
+#define ADIS16475_MSG_CTRL_DR_POL_MASK	BIT(0)
+#define ADIS16475_MSG_CTRL_DR_POL(x) \
+				FIELD_PREP(ADIS16475_MSG_CTRL_DR_POL_MA
SK, x)
+#define ADIS16475_EXT_CLK_MASK		GENMASK(4, 2)
+#define ADIS16475_EXT_CLK(x)		FIELD_PREP(ADIS16475_EX
T_CLK_MASK, x)
+#define ADIS16475_REG_UP_SCALE		0x62
+#define ADIS16475_REG_DEC_RATE		0x64
+#define ADIS16475_REG_GLOB_CMD		0x68
+#define ADIS16475_REG_FIRM_REV		0x6c
+#define ADIS16475_REG_FIRM_DM		0x6e
+#define ADIS16475_REG_FIRM_Y		0x70
+#define ADIS16475_REG_PROD_ID		0x72
+#define ADIS16475_REG_SERIAL_NUM	0x74
+#define ADIS16475_REG_FLASH_CNT		0x7c
+#define ADIS16500_BURST32_MASK		BIT(9)
+#define ADIS16500_BURST32(x)		FIELD_PREP(ADIS16500_BU
RST32_MASK, x)
+/* number of data elements in burst mode */
+#define ADIS16475_BURST_MAX_DATA	10
+#define ADIS16475_MAX_SCAN_DATA		15
+
+enum clk_mode {
+	ADIS16475_CLK_DIRECT = 1,
+	ADIS16475_CLK_SCALED,
+	ADIS16475_CLK_OUTPUT,
+	ADIS16475_CLK_PULSE = 5,
+};
+
+struct adis16475_clks {
+	const char *name;
+	enum clk_mode clk_mode;
+	u16 min_rate;
+	u16 max_rate;
+};
+
+struct adis16475_chip_info {
+	const struct iio_chan_spec *channels;
+	const struct adis16475_clks *clks;
+	const struct adis_data adis_data;
+	u32 num_channels;
+	u32 gyro_max_val;
+	u32 gyro_max_scale;
+	u32 accel_max_val;
+	u32 accel_max_scale;
+	u32 temp_scale;
+	u32 int_clk;
+	u16 max_dec;
+	u8 num_clks;
+	bool has_burst32;
+};
+
+struct adis16475 {
+	const struct adis16475_chip_info *info;
+	struct adis adis;
+	u32 clk_freq;
+	u32 cached_spi_speed_hz;
+	bool burst32;
+};
+
+enum {
+	ADIS16475_SCAN_GYRO_X,
+	ADIS16475_SCAN_GYRO_Y,
+	ADIS16475_SCAN_GYRO_Z,
+	ADIS16475_SCAN_ACCEL_X,
+	ADIS16475_SCAN_ACCEL_Y,
+	ADIS16475_SCAN_ACCEL_Z,
+	ADIS16475_SCAN_TEMP,
+	ADIS16475_SCAN_DIAG_S_FLAGS,
+	ADIS16475_SCAN_CRC_FAILURE,
+};
+
+#ifdef CONFIG_DEBUG_FS
+static ssize_t adis16475_show_firmware_revision(struct file
*file,
+						char __user *userbuf,
+						size_t count, loff_t
*ppos)
+{
+	struct adis16475 *st = file->private_data;
+	char buf[7];
+	size_t len;
+	u16 rev;
+	int ret;
+
+	ret = adis_read_reg_16(&st->adis, ADIS16475_REG_FIRM_REV,
&rev);
+	if (ret)
+		return ret;
+
+	len = scnprintf(buf, sizeof(buf), "%x.%x\n", rev >> 8, rev &
0xff);
+
+	return simple_read_from_buffer(userbuf, count, ppos, buf, len);
+}
+
+static const struct file_operations
adis16475_firmware_revision_fops = {
+	.open = simple_open,
+	.read = adis16475_show_firmware_revision,
+	.llseek = default_llseek,
+	.owner = THIS_MODULE,
+};
+
+static ssize_t adis16475_show_firmware_date(struct file *file,
+					    char __user *userbuf,
+					    size_t count, loff_t *ppos)
+{
+	struct adis16475 *st = file->private_data;
+	u16 md, year;
+	char buf[12];
+	size_t len;
+	int ret;
+
+	ret = adis_read_reg_16(&st->adis, ADIS16475_REG_FIRM_Y, &year);
+	if (ret)
+		return ret;
+
+	ret = adis_read_reg_16(&st->adis, ADIS16475_REG_FIRM_DM, &md);
+	if (ret)
+		return ret;
+
+	len = snprintf(buf, sizeof(buf), "%.2x-%.2x-%.4x\n", md >> 8,
md & 0xff,
+		       year);
+
+	return simple_read_from_buffer(userbuf, count, ppos, buf, len);
+}
+
+static const struct file_operations adis16475_firmware_date_fops
=
{
+	.open = simple_open,
+	.read = adis16475_show_firmware_date,
+	.llseek = default_llseek,
+	.owner = THIS_MODULE,
+};
+
+static int adis16475_show_serial_number(void *arg, u64 *val)
+{
+	struct adis16475 *st = arg;
+	u16 serial;
+	int ret;
+
+	ret = adis_read_reg_16(&st->adis, ADIS16475_REG_SERIAL_NUM,
&serial);
+	if (ret)
+		return ret;
+
+	*val = serial;
+
+	return 0;
+}
+DEFINE_SIMPLE_ATTRIBUTE(adis16475_serial_number_fops,
+			adis16475_show_serial_number, NULL,
"0x%.4llx\n");
+
+static int adis16475_show_product_id(void *arg, u64 *val)
+{
+	struct adis16475 *st = arg;
+	u16 prod_id;
+	int ret;
+
+	ret = adis_read_reg_16(&st->adis, ADIS16475_REG_PROD_ID,
&prod_id);
+	if (ret)
+		return ret;
+
+	*val = prod_id;
+
+	return 0;
+}
+DEFINE_SIMPLE_ATTRIBUTE(adis16475_product_id_fops,
+			adis16475_show_product_id, NULL, "%llu\n");
+
+static int adis16475_show_flash_count(void *arg, u64 *val)
+{
+	struct adis16475 *st = arg;
+	u32 flash_count;
+	int ret;
+
+	ret = adis_read_reg_32(&st->adis, ADIS16475_REG_FLASH_CNT,
+			       &flash_count);
+	if (ret)
+		return ret;
+
+	*val = flash_count;
+
+	return 0;
+}
+DEFINE_SIMPLE_ATTRIBUTE(adis16475_flash_count_fops,
+			adis16475_show_flash_count, NULL, "%lld\n");
+
+static int adis16475_debugfs_init(struct iio_dev *indio_dev)
+{
+	struct adis16475 *st = iio_priv(indio_dev);
+
+	debugfs_create_file("serial_number", 0400, indio_dev-
debugfs_dentry,
+			    st, &adis16475_serial_number_fops);
+	debugfs_create_file("product_id", 0400, indio_dev-
debugfs_dentry, st,
+			    &adis16475_product_id_fops);
+	debugfs_create_file("flash_count", 0400, indio_dev-
debugfs_dentry, st,
+			    &adis16475_flash_count_fops);
+	debugfs_create_file("firmware_revision", 0400,
+			    indio_dev->debugfs_dentry, st,
+			    &adis16475_firmware_revision_fops);
+	debugfs_create_file("firmware_date", 0400, indio_dev-
debugfs_dentry,
+			    st, &adis16475_firmware_date_fops);
+	return 0;
+}
+#else
+static int adis16475_debugfs_init(struct iio_dev *indio_dev)
+{
+	return 0;
+}
+#endif
+
+static ssize_t adis16475_burst_mode_enable_get(struct device
*dev,
+					       struct device_attribute
*attr,
+					       char *buf)
+{
+	struct adis16475 *st = iio_priv(dev_to_iio_dev(dev));
+
+	return sprintf(buf, "%d\n", st->adis.burst->en);
+}
+
+static ssize_t adis16475_burst_mode_enable_set(struct device
*dev,
+					       struct device_attribute
*attr,
+					       const char *buf, size_t
len)
+{
+	struct adis16475 *st = iio_priv(dev_to_iio_dev(dev));
+	bool val;
+	int ret;
+
+	ret = kstrtobool(buf, &val);
+	if (ret)
+		return ret;
+
+	if (val)
+		/* 1MHz max in burst mode */
+		st->adis.spi->max_speed_hz = 1000000;
+	else
+		st->adis.spi->max_speed_hz = st->cached_spi_speed_hz;
+
+	st->adis.burst->en = val;
+
+	return len;
+}
+
+static IIO_DEVICE_ATTR(burst_mode_enable, 0644,
+		       adis16475_burst_mode_enable_get,
+		       adis16475_burst_mode_enable_set, 0);
+
+static struct attribute *adis16475_attributes[] = {
+	&iio_dev_attr_burst_mode_enable.dev_attr.attr,
Hmm.  Normally we try to avoid exposing this and make the decision
automatically based on which channels are enabled.
Hmm. In that case, the decision would probably have to go to the
library since it is there that the "preparations" for buffered mode
are
done. Mostly, the data we are interested in the burst data is gyro,
accel and temp. So to make the decision based on which channels are
enabled is not that straight. Should we enable it only when all
channels are enabled? Some of them (and which)?
I thought a little bit more about it and we could do some math in the
lib to know when using burst mode becomes faster (depending on enabled
scan elements). The library would need to know about the burst max spi
frequency and also some minor changes in how burst_len is being
calculated (drivers should explicitly set this rather than the
library). The question is, is it worth it to go with this extra work
:)?

You can leave it out of the initial version and always use burst mode and then add support for this in a follow up patch if it is worth it.

- Lars




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