The MAX14001 is configurable, isolated 10-bit ADCs for multi-range
binary inputs.
Signed-off-by: Kim Seer Paller <[email protected]>
---
MAINTAINERS | 1 +
drivers/iio/adc/Kconfig | 10 ++
drivers/iio/adc/Makefile | 1 +
drivers/iio/adc/max14001.c | 333 +++++++++++++++++++++++++++++++++++++
4 files changed, 345 insertions(+)
create mode 100644 drivers/iio/adc/max14001.c
diff --git a/MAINTAINERS b/MAINTAINERS
index 766847ad2..16b74c072 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -12579,6 +12579,7 @@ L: [email protected]
S: Supported
W: https://ez.analog.com/linux-software-drivers
F: Documentation/devicetree/bindings/iio/dac/adi,max14001.yaml
+F: drivers/iio/adc/max14001.c
MAXBOTIX ULTRASONIC RANGER IIO DRIVER
M: Andreas Klinger <[email protected]>
diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index 45af2302b..2e5137471 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -706,6 +706,16 @@ config MAX11410
To compile this driver as a module, choose M here: the module will be
called max11410.
+config MAX14001
+ tristate "Analog Devices MAX14001 ADC driver"
+ depends on SPI
+ help
+ Say yes here to build support for Analog Devices MAX14001 Configurable,
+ Isolated 10-bit ADCs for Multi-Range Binary Inputs.
+
+ To compile this driver as a module, choose M here: the module will be
+ called max14001.
+
config MAX1241
tristate "Maxim max1241 ADC driver"
depends on SPI_MASTER
diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
index 36c181773..016064727 100644
--- a/drivers/iio/adc/Makefile
+++ b/drivers/iio/adc/Makefile
@@ -65,6 +65,7 @@ obj-$(CONFIG_MAX11100) += max11100.o
obj-$(CONFIG_MAX1118) += max1118.o
obj-$(CONFIG_MAX11205) += max11205.o
obj-$(CONFIG_MAX11410) += max11410.o
+obj-$(CONFIG_MAX14001) += max14001.o
obj-$(CONFIG_MAX1241) += max1241.o
obj-$(CONFIG_MAX1363) += max1363.o
obj-$(CONFIG_MAX9611) += max9611.o
diff --git a/drivers/iio/adc/max14001.c b/drivers/iio/adc/max14001.c
new file mode 100644
index 000000000..7c5272756
--- /dev/null
+++ b/drivers/iio/adc/max14001.c
@@ -0,0 +1,333 @@
+// SPDX-License-Identifier: (GPL-2.0-only OR BSD-3-Clause)
+/*
+ * Analog Devices MAX14001 ADC driver
+ *
+ * Copyright 2023 Analog Devices Inc.
+ */
+
+#include <linux/bitfield.h>
+#include <linux/bitrev.h>
+#include <linux/device.h>
+#include <linux/iio/iio.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mod_devicetable.h>
+#include <linux/property.h>
+#include <linux/regmap.h>
+#include <linux/regulator/consumer.h>
+#include <linux/spi/spi.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+
+#include <asm/unaligned.h>
+
+/* MAX14001 Registers Address */
+#define MAX14001_ADC 0x00
+#define MAX14001_FADC 0x01
+#define MAX14001_FLAGS 0x02
+#define MAX14001_FLTEN 0x03
+#define MAX14001_THL 0x04
+#define MAX14001_THU 0x05
+#define MAX14001_INRR 0x06
+#define MAX14001_INRT 0x07
+#define MAX14001_INRP 0x08
+#define MAX14001_CFG 0x09
+#define MAX14001_ENBL 0x0A
+#define MAX14001_ACT 0x0B
+#define MAX14001_WEN 0x0C
+
+#define MAX14001_VERIFICATION_REG(x) ((x) + 0x10)
+
+#define MAX14001_CFG_EXRF BIT(5)
+
+#define MAX14001_ADDR_MASK GENMASK(15, 11)
+#define MAX14001_DATA_MASK GENMASK(9, 0)
+#define MAX14001_FILTER_MASK GENMASK(3, 2)
+
+#define MAX14001_SET_WRITE_BIT BIT(10)
+#define MAX14001_WRITE_WEN 0x294
+
+struct max14001_state {
+ struct spi_device *spi;
+ /* lock protect agains multiple concurrent accesses */
+ struct mutex lock;
+ struct regmap *regmap;
+ int vref_mv;
+ /*
+ * DMA (thus cache coherency maintenance) requires the
+ * transfer buffers to live in their own cache lines.
+ */
+ __be16 spi_tx_buffer ____cacheline_aligned;
+ __be16 spi_rx_buffer;
+};
+
+static int max14001_read(void *context, unsigned int reg_addr,
+ unsigned int *data)
+{
+ struct max14001_state *st = context;
+ u16 tx = 0;
+ int ret;
+
+ struct spi_transfer xfers[] = {
+ {
+ .tx_buf = &st->spi_tx_buffer,
+ .len = 2,
+ .cs_change = 1,
+ }, {
+ .rx_buf = &st->spi_rx_buffer,
+ .len = 2,
+ },
+ };
+
+ tx = FIELD_PREP(MAX14001_ADDR_MASK, reg_addr);
+ st->spi_tx_buffer = bitrev16(cpu_to_be16(tx));
+
+ ret = spi_sync_transfer(st->spi, xfers, ARRAY_SIZE(xfers));
+ if (ret)
+ return ret;
+
+ *data = bitrev16(be16_to_cpu(st->spi_rx_buffer)) & MAX14001_DATA_MASK;
+
+ return 0;
+}
+
+static int max14001_write(void *context, unsigned int reg_addr,
+ unsigned int data)
+{
+ struct max14001_state *st = context;
+ u16 tx = 0;
+
+ tx = FIELD_PREP(MAX14001_ADDR_MASK, reg_addr);
+ tx |= FIELD_PREP(MAX14001_SET_WRITE_BIT, 1);
+ tx |= FIELD_PREP(MAX14001_DATA_MASK, data);
+
+ st->spi_tx_buffer = bitrev16(cpu_to_be16(tx));
+
+ return spi_write(st->spi, &st->spi_tx_buffer, 2);
+}
+
+static int max14001_write_verification_reg(struct max14001_state *st,
+ unsigned int reg_addr)
+{
+ unsigned int reg_data;
+ int ret;
+
+ ret = max14001_read(st, reg_addr, ®_data);
+ if (ret)
+ return ret;
+
+ return max14001_write(st, MAX14001_VERIFICATION_REG(reg_addr),
+ reg_data);
+}
+
+static int max14001_reg_update(struct max14001_state *st,
+ unsigned int reg_addr,
+ unsigned int mask,
+ unsigned int val)
+{
+ int ret;
+
+ /* Enable SPI Registers Write */
+ ret = max14001_write(st, MAX14001_WEN, MAX14001_WRITE_WEN);
+ if (ret)
+ return ret;
+
+ ret = regmap_update_bits(st->regmap, reg_addr, mask, val);
+ if (ret)
+ return ret;
+
+ ret = max14001_write_verification_reg(st, reg_addr);
+ if (ret)
+ return ret;
+
+ /* Disable SPI Registers Write */
+ return max14001_write(st, MAX14001_WEN, 0);
+}
+
+static int max14001_read_raw(struct iio_dev *indio_dev,
+ struct iio_chan_spec const *chan,
+ int *val, int *val2, long mask)
+{
+ struct max14001_state *st = iio_priv(indio_dev);
+ unsigned int data;
+ int ret;
+
+ switch (mask) {
+ case IIO_CHAN_INFO_RAW:
+ mutex_lock(&st->lock);
+ ret = max14001_read(st, MAX14001_ADC, &data);
+ mutex_unlock(&st->lock);
+ if (ret < 0)
+ return ret;
+
+ *val = data;
+
+ return IIO_VAL_INT;
+
+ case IIO_CHAN_INFO_SCALE:
+ *val = st->vref_mv;
+ *val2 = 10;
+
+ return IIO_VAL_FRACTIONAL_LOG2;
+
+ default:
+ return -EINVAL;
+ }
+}
+
+static const struct regmap_config max14001_regmap_config = {
+ .reg_read = max14001_read,
+ .reg_write = max14001_write,
+};
+
+static const struct iio_info max14001_info = {
+ .read_raw = max14001_read_raw,
+};
+
+static const struct iio_chan_spec max14001_channels[] = {
+ {
+ .type = IIO_VOLTAGE,
+ .channel = 0,
+ .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
+ BIT(IIO_CHAN_INFO_SCALE),
+ }
+};
+
+static void max14001_regulator_disable(void *data)
+{
+ struct regulator *reg = data;
+
+ regulator_disable(reg);
+}
+
+static int max14001_init(struct max14001_state *st)
+{
+ int ret;
+
+ /* Enable SPI Registers Write */
+ ret = max14001_write(st, MAX14001_WEN, MAX14001_WRITE_WEN);
+ if (ret)
+ return ret;
+
+ /*
+ * Reads all registers and writes the values back to their appropriate
+ * verification registers to clear the Memory Validation fault.
+ */
+ ret = max14001_write_verification_reg(st, MAX14001_FLTEN);
+ if (ret)
+ return ret;
+
+ ret = max14001_write_verification_reg(st, MAX14001_THL);
+ if (ret)
+ return ret;
+
+ ret = max14001_write_verification_reg(st, MAX14001_THU);
+ if (ret)
+ return ret;
+
+ ret = max14001_write_verification_reg(st, MAX14001_INRR);
+ if (ret)
+ return ret;
+
+ ret = max14001_write_verification_reg(st, MAX14001_INRT);
+ if (ret)
+ return ret;
+
+ ret = max14001_write_verification_reg(st, MAX14001_INRP);
+ if (ret)
+ return ret;
+
+ ret = max14001_write_verification_reg(st, MAX14001_CFG);
+ if (ret)
+ return ret;
+
+ ret = max14001_write_verification_reg(st, MAX14001_ENBL);
+ if (ret)
+ return ret;
+
+ /* Disable SPI Registers Write */
+ return max14001_write(st, MAX14001_WEN, 0);
+}
+
+static int max14001_probe(struct spi_device *spi)
+{
+ struct iio_dev *indio_dev;
+ struct max14001_state *st;
+ struct regulator *vref;
+ int ret;
+
+ indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*st));
+ if (!indio_dev)
+ return -ENOMEM;
+
+ st = iio_priv(indio_dev);
+ st->spi = spi;
+
+ st->regmap = devm_regmap_init(&spi->dev, NULL, st,
+ &max14001_regmap_config);
+
+ indio_dev->name = "max14001";
+ indio_dev->info = &max14001_info;
+ indio_dev->channels = max14001_channels;
+ indio_dev->num_channels = ARRAY_SIZE(max14001_channels);
+ indio_dev->modes = INDIO_DIRECT_MODE;
+
+ ret = max14001_init(st);
+ if (ret)
+ return ret;
+
+ vref = devm_regulator_get_optional(&spi->dev, "vref");
+ if (IS_ERR(vref)) {
+ if (PTR_ERR(vref) != -ENODEV)
+ return dev_err_probe(&spi->dev, PTR_ERR(vref),
+ "Failed to get vref regulator");
+
+ /* internal reference */
+ st->vref_mv = 1250;
+ } else {
+ ret = regulator_enable(vref);
+ if (ret)
+ return dev_err_probe(&spi->dev, ret,
+ "Failed to enable vref regulators\n");
+
+ ret = devm_add_action_or_reset(&spi->dev,
+ max14001_regulator_disable,
+ vref);
+ if (ret)
+ return ret;
+
+ /* enable external voltage reference */
+ ret = max14001_reg_update(st, MAX14001_CFG,
+ MAX14001_CFG_EXRF, 1);
+
+ ret = regulator_get_voltage(vref);
+ if (ret < 0)
+ return dev_err_probe(&spi->dev, ret,
+ "Failed to get vref\n");
+
+ st->vref_mv = ret / 1000;
+ }
+
+ mutex_init(&st->lock);
+
+ return devm_iio_device_register(&spi->dev, indio_dev);
+}
+
+static const struct of_device_id max14001_of_match[] = {
+ { .compatible = "adi,max14001" },
+ { }
+};
+MODULE_DEVICE_TABLE(of, max14001_of_match);
+
+static struct spi_driver max14001_driver = {
+ .driver = {
+ .name = "max14001",
+ .of_match_table = max14001_of_match,
+ },
+ .probe = max14001_probe,
+};
+module_spi_driver(max14001_driver);
+
+MODULE_AUTHOR("Kim Seer Paller");
+MODULE_DESCRIPTION("MAX14001 ADC driver");
+MODULE_LICENSE("GPL");
--
2.34.1
On Mon, 5 Jun 2023 21:07:55 +0800
Kim Seer Paller <[email protected]> wrote:
> The MAX14001 is configurable, isolated 10-bit ADCs for multi-range
> binary inputs.
>
> Signed-off-by: Kim Seer Paller <[email protected]>
> ---
...
Hi Kim,
A few comments inline.
> diff --git a/drivers/iio/adc/max14001.c b/drivers/iio/adc/max14001.c
> new file mode 100644
> index 000000000..7c5272756
> --- /dev/null
> +++ b/drivers/iio/adc/max14001.c
> @@ -0,0 +1,333 @@
> +// SPDX-License-Identifier: (GPL-2.0-only OR BSD-3-Clause)
> +/*
> + * Analog Devices MAX14001 ADC driver
> + *
> + * Copyright 2023 Analog Devices Inc.
> + */
> +
> +#include <linux/bitfield.h>
> +#include <linux/bitrev.h>
> +#include <linux/device.h>
> +#include <linux/iio/iio.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/mod_devicetable.h>
> +#include <linux/property.h>
> +#include <linux/regmap.h>
> +#include <linux/regulator/consumer.h>
> +#include <linux/spi/spi.h>
> +#include <linux/slab.h>
> +#include <linux/types.h>
> +
> +#include <asm/unaligned.h>
> +
> +/* MAX14001 Registers Address */
> +#define MAX14001_ADC 0x00
> +#define MAX14001_FADC 0x01
> +#define MAX14001_FLAGS 0x02
> +#define MAX14001_FLTEN 0x03
> +#define MAX14001_THL 0x04
> +#define MAX14001_THU 0x05
> +#define MAX14001_INRR 0x06
> +#define MAX14001_INRT 0x07
> +#define MAX14001_INRP 0x08
> +#define MAX14001_CFG 0x09
> +#define MAX14001_ENBL 0x0A
> +#define MAX14001_ACT 0x0B
> +#define MAX14001_WEN 0x0C
> +
> +#define MAX14001_VERIFICATION_REG(x) ((x) + 0x10)
> +
> +#define MAX14001_CFG_EXRF BIT(5)
> +
> +#define MAX14001_ADDR_MASK GENMASK(15, 11)
> +#define MAX14001_DATA_MASK GENMASK(9, 0)
> +#define MAX14001_FILTER_MASK GENMASK(3, 2)
> +
> +#define MAX14001_SET_WRITE_BIT BIT(10)
> +#define MAX14001_WRITE_WEN 0x294
> +
> +struct max14001_state {
> + struct spi_device *spi;
> + /* lock protect agains multiple concurrent accesses */
To what? Here I suspect it's RMW sequence on device and perhaps
more importantly the buffers below.
> + struct mutex lock;
> + struct regmap *regmap;
> + int vref_mv;
> + /*
> + * DMA (thus cache coherency maintenance) requires the
> + * transfer buffers to live in their own cache lines.
You are looking at an old kernel I guess - we fixed all of these - and
introduced IIO_DMA_MINALIGN for __aligned(IIO_DMA_MINALIGN) to make
it easier to fix any such problems in future.
Upshot is that ___cacheline_aligned aligns to the l1 cacheline length.
Some fun systems (such as the big servers I use in my dayjob) have higher
cacheline sizes for their larger / further from CPU caches.
One group of SoCs out there is known to both do non coherent DMA and have
a larger line size for the bit relevant to that than ___cacheline_aligned
gives you. So on that rare platform this is currently broken.
> + */
> + __be16 spi_tx_buffer ____cacheline_aligned;
> + __be16 spi_rx_buffer;
> +};
> +
> +static int max14001_read(void *context, unsigned int reg_addr,
> + unsigned int *data)
> +{
> + struct max14001_state *st = context;
> + u16 tx = 0;
> + int ret;
> +
> + struct spi_transfer xfers[] = {
> + {
> + .tx_buf = &st->spi_tx_buffer,
> + .len = 2,
> + .cs_change = 1,
> + }, {
> + .rx_buf = &st->spi_rx_buffer,
> + .len = 2,
> + },
> + };
> +
> + tx = FIELD_PREP(MAX14001_ADDR_MASK, reg_addr);
> + st->spi_tx_buffer = bitrev16(cpu_to_be16(tx));
> +
> + ret = spi_sync_transfer(st->spi, xfers, ARRAY_SIZE(xfers));
> + if (ret)
> + return ret;
> +
> + *data = bitrev16(be16_to_cpu(st->spi_rx_buffer)) & MAX14001_DATA_MASK;
> +
> + return 0;
> +}
> +
> +static int max14001_write(void *context, unsigned int reg_addr,
> + unsigned int data)
> +{
> + struct max14001_state *st = context;
> + u16 tx = 0;
> +
> + tx = FIELD_PREP(MAX14001_ADDR_MASK, reg_addr);
> + tx |= FIELD_PREP(MAX14001_SET_WRITE_BIT, 1);
> + tx |= FIELD_PREP(MAX14001_DATA_MASK, data);
> +
> + st->spi_tx_buffer = bitrev16(cpu_to_be16(tx));
> +
> + return spi_write(st->spi, &st->spi_tx_buffer, 2);
> +}
> +
> +static int max14001_write_verification_reg(struct max14001_state *st,
> + unsigned int reg_addr)
> +{
> + unsigned int reg_data;
> + int ret;
> +
> + ret = max14001_read(st, reg_addr, ®_data);
> + if (ret)
> + return ret;
> +
> + return max14001_write(st, MAX14001_VERIFICATION_REG(reg_addr),
> + reg_data);
Even though this is a bit unusual, I'd still expect this to use
the regmap_read / regmap_write interfaces not directly use the callbacks.
> +}
> +
> +static int max14001_reg_update(struct max14001_state *st,
> + unsigned int reg_addr,
> + unsigned int mask,
> + unsigned int val)
> +{
> + int ret;
> +
> + /* Enable SPI Registers Write */
> + ret = max14001_write(st, MAX14001_WEN, MAX14001_WRITE_WEN);
Mixing regmap and non regmap rather defeats the point of
having a standard interface. Use regmap_read and regmap_write
throughout or not at all.
> + if (ret)
> + return ret;
> +
> + ret = regmap_update_bits(st->regmap, reg_addr, mask, val);
> + if (ret)
> + return ret;
> +
> + ret = max14001_write_verification_reg(st, reg_addr);
> + if (ret)
> + return ret;
> +
> + /* Disable SPI Registers Write */
> + return max14001_write(st, MAX14001_WEN, 0);
> +}
> +
> +static int max14001_read_raw(struct iio_dev *indio_dev,
> + struct iio_chan_spec const *chan,
> + int *val, int *val2, long mask)
> +{
> + struct max14001_state *st = iio_priv(indio_dev);
> + unsigned int data;
> + int ret;
> +
> + switch (mask) {
> + case IIO_CHAN_INFO_RAW:
> + mutex_lock(&st->lock);
> + ret = max14001_read(st, MAX14001_ADC, &data);
> + mutex_unlock(&st->lock);
> + if (ret < 0)
> + return ret;
> +
> + *val = data;
> +
> + return IIO_VAL_INT;
> +
> + case IIO_CHAN_INFO_SCALE:
> + *val = st->vref_mv;
> + *val2 = 10;
> +
> + return IIO_VAL_FRACTIONAL_LOG2;
> +
> + default:
> + return -EINVAL;
> + }
> +}
> +
> +static const struct regmap_config max14001_regmap_config = {
> + .reg_read = max14001_read,
> + .reg_write = max14001_write,
I'd keep this up by the callbacks, so all the regmap setup stuff
is in one place.
> +};
> +
> +static const struct iio_info max14001_info = {
> + .read_raw = max14001_read_raw,
> +};
> +
...
> +static int max14001_probe(struct spi_device *spi)
> +{
...
> +
> + vref = devm_regulator_get_optional(&spi->dev, "vref");
> + if (IS_ERR(vref)) {
> + if (PTR_ERR(vref) != -ENODEV)
> + return dev_err_probe(&spi->dev, PTR_ERR(vref),
> + "Failed to get vref regulator");
> +
> + /* internal reference */
> + st->vref_mv = 1250;
> + } else {
> + ret = regulator_enable(vref);
> + if (ret)
> + return dev_err_probe(&spi->dev, ret,
> + "Failed to enable vref regulators\n");
> +
> + ret = devm_add_action_or_reset(&spi->dev,
> + max14001_regulator_disable,
> + vref);
> + if (ret)
> + return ret;
> +
> + /* enable external voltage reference */
use external voltage reference?
It's enabled by the regulator_enable() above, not this line.
> + ret = max14001_reg_update(st, MAX14001_CFG,
> + MAX14001_CFG_EXRF, 1);
> +
> + ret = regulator_get_voltage(vref);
> + if (ret < 0)
> + return dev_err_probe(&spi->dev, ret,
> + "Failed to get vref\n");
> +
> + st->vref_mv = ret / 1000;
> + }
> +
> + mutex_init(&st->lock);
> +
> + return devm_iio_device_register(&spi->dev, indio_dev);
> +}
Mon, Jun 05, 2023 at 09:07:55PM +0800, Kim Seer Paller kirjoitti:
> The MAX14001 is configurable, isolated 10-bit ADCs for multi-range
> binary inputs.
First question, why don't you use regmap SPI?
...
> +static int max14001_read(void *context, unsigned int reg_addr,
> + unsigned int *data)
Strange indentation.
> +{
> + struct max14001_state *st = context;
> + u16 tx = 0;
Redundant assignment.
> + int ret;
> +
> + struct spi_transfer xfers[] = {
> + {
> + .tx_buf = &st->spi_tx_buffer,
> + .len = 2,
> + .cs_change = 1,
> + }, {
> + .rx_buf = &st->spi_rx_buffer,
> + .len = 2,
> + },
> + };
> +
> + tx = FIELD_PREP(MAX14001_ADDR_MASK, reg_addr);
> + st->spi_tx_buffer = bitrev16(cpu_to_be16(tx));
This is strange. Why this monsteur construct with bitrev16() is used?
According to the datasheet, the bit stream is LE16, where 10 LSB is data,
5 MSB is address and bit 11 is R/W.
> + ret = spi_sync_transfer(st->spi, xfers, ARRAY_SIZE(xfers));
> + if (ret)
> + return ret;
> + *data = bitrev16(be16_to_cpu(st->spi_rx_buffer)) & MAX14001_DATA_MASK;
Ditto.
> + return 0;
> +}
> +static int max14001_write(void *context, unsigned int reg_addr,
> + unsigned int data)
> +{
> + struct max14001_state *st = context;
> + u16 tx = 0;
Redundant assignment.
> + tx = FIELD_PREP(MAX14001_ADDR_MASK, reg_addr);
> + tx |= FIELD_PREP(MAX14001_SET_WRITE_BIT, 1);
> + tx |= FIELD_PREP(MAX14001_DATA_MASK, data);
> +
> + st->spi_tx_buffer = bitrev16(cpu_to_be16(tx));
> +
> + return spi_write(st->spi, &st->spi_tx_buffer, 2);
sizeof() ?
> +}
...
> + return dev_err_probe(&spi->dev, PTR_ERR(vref),
> + "Failed to get vref regulator");
With
struct device *dev = &spi->dev;
this and other calls in this function can be made neater.
--
With Best Regards,
Andy Shevchenko
> -----Original Message-----
> From: [email protected] <[email protected]>
> Sent: Tuesday, June 6, 2023 8:49 AM
> To: Paller, Kim Seer <[email protected]>
> Cc: [email protected]; [email protected]; [email protected];
> [email protected]; [email protected]; [email protected]; linux-
> [email protected]
> Subject: Re: [PATCH v2 2/2] iio: adc: max14001: New driver
>
> [External]
>
> Mon, Jun 05, 2023 at 09:07:55PM +0800, Kim Seer Paller kirjoitti:
> > The MAX14001 is configurable, isolated 10-bit ADCs for multi-range
> > binary inputs.
>
> First question, why don't you use regmap SPI?
I found it difficult to implement the regmap interface due to the timing diagram
requirements. The chip select needs to be changed between transfers, which, as
far as I know, does not work with regmap. Additionally, the regmap_config
parameters, specifically reg_bits and val_bits, cannot be set to specific values.
This limitation makes it challenging to accommodate specific configurations
such as using 5 bits for register address and 10 bits for data.
>
> ...
>
> > +static int max14001_read(void *context, unsigned int reg_addr,
> > + unsigned int *data)
>
> Strange indentation.
>
> > +{
> > + struct max14001_state *st = context;
> > + u16 tx = 0;
>
> Redundant assignment.
>
> > + int ret;
> > +
> > + struct spi_transfer xfers[] = {
> > + {
> > + .tx_buf = &st->spi_tx_buffer,
> > + .len = 2,
> > + .cs_change = 1,
> > + }, {
> > + .rx_buf = &st->spi_rx_buffer,
> > + .len = 2,
> > + },
> > + };
> > +
> > + tx = FIELD_PREP(MAX14001_ADDR_MASK, reg_addr);
>
> > + st->spi_tx_buffer = bitrev16(cpu_to_be16(tx));
>
> This is strange. Why this monsteur construct with bitrev16() is used?
>
> According to the datasheet, the bit stream is LE16, where 10 LSB is data,
> 5 MSB is address and bit 11 is R/W.
I discovered that following the instructions in the application note made
the implementation much easier.
https://www.analog.com/media/en/technical-documentation/user-guides/guide-to-programming-the-max14001max14002-isolated-adcs--maxim-integrated.pdf
To ensure compatibility with the device, I changed the format to big
endian and reversed the data before sending it to the device.
This is why I used the "bitrev" function. I'm happy to report that
this approach worked perfectly.
>
> > + ret = spi_sync_transfer(st->spi, xfers, ARRAY_SIZE(xfers));
> > + if (ret)
> > + return ret;
>
> > + *data = bitrev16(be16_to_cpu(st->spi_rx_buffer)) &
> > +MAX14001_DATA_MASK;
>
> Ditto.
>
> > + return 0;
> > +}
>
> > +static int max14001_write(void *context, unsigned int reg_addr,
> > + unsigned int data)
> > +{
> > + struct max14001_state *st = context;
> > + u16 tx = 0;
>
> Redundant assignment.
>
> > + tx = FIELD_PREP(MAX14001_ADDR_MASK, reg_addr);
> > + tx |= FIELD_PREP(MAX14001_SET_WRITE_BIT, 1);
> > + tx |= FIELD_PREP(MAX14001_DATA_MASK, data);
> > +
> > + st->spi_tx_buffer = bitrev16(cpu_to_be16(tx));
> > +
> > + return spi_write(st->spi, &st->spi_tx_buffer, 2);
>
> sizeof() ?
>
> > +}
>
> ...
>
> > + return dev_err_probe(&spi->dev, PTR_ERR(vref),
> > + "Failed to get vref regulator");
>
> With
>
> struct device *dev = &spi->dev;
>
> this and other calls in this function can be made neater.
>
> --
> With Best Regards,
> Andy Shevchenko
>
> -----Original Message-----
> From: Jonathan Cameron <[email protected]>
> Sent: Tuesday, June 6, 2023 3:24 AM
> To: Paller, Kim Seer <[email protected]>
> Cc: [email protected]; [email protected]; [email protected];
> [email protected]; [email protected]; linux-
> [email protected]
> Subject: Re: [PATCH v2 2/2] iio: adc: max14001: New driver
>
> [External]
>
> On Mon, 5 Jun 2023 21:07:55 +0800
> Kim Seer Paller <[email protected]> wrote:
>
> > The MAX14001 is configurable, isolated 10-bit ADCs for multi-range
> > binary inputs.
> >
> > Signed-off-by: Kim Seer Paller <[email protected]>
> > ---
> ...
>
> Hi Kim,
>
> A few comments inline.
>
> > diff --git a/drivers/iio/adc/max14001.c b/drivers/iio/adc/max14001.c
> > new file mode 100644 index 000000000..7c5272756
> > --- /dev/null
> > +++ b/drivers/iio/adc/max14001.c
> > @@ -0,0 +1,333 @@
> > +// SPDX-License-Identifier: (GPL-2.0-only OR BSD-3-Clause)
> > +/*
> > + * Analog Devices MAX14001 ADC driver
> > + *
> > + * Copyright 2023 Analog Devices Inc.
> > + */
> > +
> > +#include <linux/bitfield.h>
> > +#include <linux/bitrev.h>
> > +#include <linux/device.h>
> > +#include <linux/iio/iio.h>
> > +#include <linux/kernel.h>
> > +#include <linux/module.h>
> > +#include <linux/mod_devicetable.h>
> > +#include <linux/property.h>
> > +#include <linux/regmap.h>
> > +#include <linux/regulator/consumer.h> #include <linux/spi/spi.h>
> > +#include <linux/slab.h> #include <linux/types.h>
> > +
> > +#include <asm/unaligned.h>
> > +
> > +/* MAX14001 Registers Address */
> > +#define MAX14001_ADC 0x00
> > +#define MAX14001_FADC 0x01
> > +#define MAX14001_FLAGS 0x02
> > +#define MAX14001_FLTEN 0x03
> > +#define MAX14001_THL 0x04
> > +#define MAX14001_THU 0x05
> > +#define MAX14001_INRR 0x06
> > +#define MAX14001_INRT 0x07
> > +#define MAX14001_INRP 0x08
> > +#define MAX14001_CFG 0x09
> > +#define MAX14001_ENBL 0x0A
> > +#define MAX14001_ACT 0x0B
> > +#define MAX14001_WEN 0x0C
> > +
> > +#define MAX14001_VERIFICATION_REG(x) ((x) + 0x10)
> > +
> > +#define MAX14001_CFG_EXRF BIT(5)
> > +
> > +#define MAX14001_ADDR_MASK GENMASK(15, 11)
> > +#define MAX14001_DATA_MASK GENMASK(9, 0)
> > +#define MAX14001_FILTER_MASK GENMASK(3, 2)
> > +
> > +#define MAX14001_SET_WRITE_BIT BIT(10)
> > +#define MAX14001_WRITE_WEN 0x294
> > +
> > +struct max14001_state {
> > + struct spi_device *spi;
> > + /* lock protect agains multiple concurrent accesses */
>
> To what? Here I suspect it's RMW sequence on device and perhaps more
> importantly the buffers below.
>
> > + struct mutex lock;
> > + struct regmap *regmap;
> > + int vref_mv;
> > + /*
> > + * DMA (thus cache coherency maintenance) requires the
> > + * transfer buffers to live in their own cache lines.
>
> You are looking at an old kernel I guess - we fixed all of these - and
> introduced IIO_DMA_MINALIGN for __aligned(IIO_DMA_MINALIGN) to
> make it easier to fix any such problems in future.
>
> Upshot is that ___cacheline_aligned aligns to the l1 cacheline length.
> Some fun systems (such as the big servers I use in my dayjob) have higher
> cacheline sizes for their larger / further from CPU caches.
> One group of SoCs out there is known to both do non coherent DMA and
> have a larger line size for the bit relevant to that than ___cacheline_aligned
> gives you. So on that rare platform this is currently broken.
It's good to know. Given this information, is there anything specific that I
need to change in the code or implementation related to
the ___cacheline_aligned part?
>
> > + */
> > + __be16 spi_tx_buffer ____cacheline_aligned;
> > + __be16 spi_rx_buffer;
> > +};
> > +
> > +static int max14001_read(void *context, unsigned int reg_addr,
> > + unsigned int *data)
> > +{
> > + struct max14001_state *st = context;
> > + u16 tx = 0;
> > + int ret;
> > +
> > + struct spi_transfer xfers[] = {
> > + {
> > + .tx_buf = &st->spi_tx_buffer,
> > + .len = 2,
> > + .cs_change = 1,
> > + }, {
> > + .rx_buf = &st->spi_rx_buffer,
> > + .len = 2,
> > + },
> > + };
> > +
> > + tx = FIELD_PREP(MAX14001_ADDR_MASK, reg_addr);
> > + st->spi_tx_buffer = bitrev16(cpu_to_be16(tx));
> > +
> > + ret = spi_sync_transfer(st->spi, xfers, ARRAY_SIZE(xfers));
> > + if (ret)
> > + return ret;
> > +
> > + *data = bitrev16(be16_to_cpu(st->spi_rx_buffer)) &
> > +MAX14001_DATA_MASK;
> > +
> > + return 0;
> > +}
> > +
> > +static int max14001_write(void *context, unsigned int reg_addr,
> > + unsigned int data)
> > +{
> > + struct max14001_state *st = context;
> > + u16 tx = 0;
> > +
> > + tx = FIELD_PREP(MAX14001_ADDR_MASK, reg_addr);
> > + tx |= FIELD_PREP(MAX14001_SET_WRITE_BIT, 1);
> > + tx |= FIELD_PREP(MAX14001_DATA_MASK, data);
> > +
> > + st->spi_tx_buffer = bitrev16(cpu_to_be16(tx));
> > +
> > + return spi_write(st->spi, &st->spi_tx_buffer, 2); }
> > +
> > +static int max14001_write_verification_reg(struct max14001_state *st,
> > + unsigned int reg_addr)
> > +{
> > + unsigned int reg_data;
> > + int ret;
> > +
> > + ret = max14001_read(st, reg_addr, ®_data);
> > + if (ret)
> > + return ret;
> > +
> > + return max14001_write(st,
> MAX14001_VERIFICATION_REG(reg_addr),
> > + reg_data);
>
> Even though this is a bit unusual, I'd still expect this to use the regmap_read /
> regmap_write interfaces not directly use the callbacks.
>
> > +}
> > +
> > +static int max14001_reg_update(struct max14001_state *st,
> > + unsigned int reg_addr,
> > + unsigned int mask,
> > + unsigned int val)
> > +{
> > + int ret;
> > +
> > + /* Enable SPI Registers Write */
> > + ret = max14001_write(st, MAX14001_WEN,
> MAX14001_WRITE_WEN);
>
> Mixing regmap and non regmap rather defeats the point of having a standard
> interface. Use regmap_read and regmap_write throughout or not at all.
I found it difficult to implement the regmap interface due to the timing diagram
requirements. The chip select needs to be changed between transfers, which,
as far as I know, does not work with regmap. Perhaps, I will consider sticking
to the non-regmap approach.
>
> > + if (ret)
> > + return ret;
> > +
> > + ret = regmap_update_bits(st->regmap, reg_addr, mask, val);
> > + if (ret)
> > + return ret;
> > +
> > + ret = max14001_write_verification_reg(st, reg_addr);
> > + if (ret)
> > + return ret;
> > +
> > + /* Disable SPI Registers Write */
> > + return max14001_write(st, MAX14001_WEN, 0); }
> > +
> > +static int max14001_read_raw(struct iio_dev *indio_dev,
> > + struct iio_chan_spec const *chan,
> > + int *val, int *val2, long mask) {
> > + struct max14001_state *st = iio_priv(indio_dev);
> > + unsigned int data;
> > + int ret;
> > +
> > + switch (mask) {
> > + case IIO_CHAN_INFO_RAW:
> > + mutex_lock(&st->lock);
> > + ret = max14001_read(st, MAX14001_ADC, &data);
> > + mutex_unlock(&st->lock);
> > + if (ret < 0)
> > + return ret;
> > +
> > + *val = data;
> > +
> > + return IIO_VAL_INT;
> > +
> > + case IIO_CHAN_INFO_SCALE:
> > + *val = st->vref_mv;
> > + *val2 = 10;
> > +
> > + return IIO_VAL_FRACTIONAL_LOG2;
> > +
> > + default:
> > + return -EINVAL;
> > + }
> > +}
> > +
> > +static const struct regmap_config max14001_regmap_config = {
> > + .reg_read = max14001_read,
> > + .reg_write = max14001_write,
>
> I'd keep this up by the callbacks, so all the regmap setup stuff is in one place.
>
> > +};
> > +
> > +static const struct iio_info max14001_info = {
> > + .read_raw = max14001_read_raw,
> > +};
> > +
>
> ...
>
> > +static int max14001_probe(struct spi_device *spi) {
>
> ...
>
> > +
> > + vref = devm_regulator_get_optional(&spi->dev, "vref");
> > + if (IS_ERR(vref)) {
> > + if (PTR_ERR(vref) != -ENODEV)
> > + return dev_err_probe(&spi->dev, PTR_ERR(vref),
> > + "Failed to get vref regulator");
> > +
> > + /* internal reference */
> > + st->vref_mv = 1250;
> > + } else {
> > + ret = regulator_enable(vref);
> > + if (ret)
> > + return dev_err_probe(&spi->dev, ret,
> > + "Failed to enable vref regulators\n");
> > +
> > + ret = devm_add_action_or_reset(&spi->dev,
> > + max14001_regulator_disable,
> > + vref);
> > + if (ret)
> > + return ret;
> > +
> > + /* enable external voltage reference */
>
> use external voltage reference?
>
> It's enabled by the regulator_enable() above, not this line.
What I meant was to enable the CFG register to utilize the external voltage
source within the ADC. I've missed to specify the comment on this one.
>
> > + ret = max14001_reg_update(st, MAX14001_CFG,
> > + MAX14001_CFG_EXRF, 1);
> > +
> > + ret = regulator_get_voltage(vref);
> > + if (ret < 0)
> > + return dev_err_probe(&spi->dev, ret,
> > + "Failed to get vref\n");
> > +
> > + st->vref_mv = ret / 1000;
> > + }
> > +
> > + mutex_init(&st->lock);
> > +
> > + return devm_iio_device_register(&spi->dev, indio_dev); }
> -----Original Message-----
> From: Jonathan Cameron <[email protected]>
> Sent: Tuesday, June 6, 2023 6:36 PM
> To: Paller, Kim Seer <[email protected]>
> Cc: Jonathan Cameron <[email protected]>; [email protected];
> [email protected]; [email protected]; [email protected];
> [email protected]; [email protected]
> Subject: Re: [PATCH v2 2/2] iio: adc: max14001: New driver
>
> [External]
>
>
>
> > >
> > > > + struct mutex lock;
> > > > + struct regmap *regmap;
> > > > + int vref_mv;
> > > > + /*
> > > > + * DMA (thus cache coherency maintenance) requires the
> > > > + * transfer buffers to live in their own cache lines.
> > >
> > > You are looking at an old kernel I guess - we fixed all of these - and
> > > introduced IIO_DMA_MINALIGN for __aligned(IIO_DMA_MINALIGN) to
> > > make it easier to fix any such problems in future.
> > >
> > > Upshot is that ___cacheline_aligned aligns to the l1 cacheline length.
> > > Some fun systems (such as the big servers I use in my dayjob) have higher
> > > cacheline sizes for their larger / further from CPU caches.
> > > One group of SoCs out there is known to both do non coherent DMA and
> > > have a larger line size for the bit relevant to that than ___cacheline_aligned
> > > gives you. So on that rare platform this is currently broken.
> >
> > It's good to know. Given this information, is there anything specific that I
> > need to change in the code or implementation related to
> > the ___cacheline_aligned part?
>
> Replace it with __aligned(IIO_DMA_MINALIGN) as has hopefully now been
> done
> in all upstream drivers.
When I attempted to implement this change, I encountered a checkpatch warning
in the latest kernel version. The warning indicated that externs should be avoided
in .c files and emphasized the need for an identifier name for the function
definition argument 'IIO_DMA_MINALIGN'. I attempted to define a macro with an
appropriate identifier name, but I still received the same checkpatch warning.
It's possible that I may have overlooked something in my approach. I would
appreciate your thoughts and insights on this matter. Thanks.
>
> > >
>
> > > > +}
> > > > +
> > > > +static int max14001_reg_update(struct max14001_state *st,
> > > > + unsigned int reg_addr,
> > > > + unsigned int mask,
> > > > + unsigned int val)
> > > > +{
> > > > + int ret;
> > > > +
> > > > + /* Enable SPI Registers Write */
> > > > + ret = max14001_write(st, MAX14001_WEN,
> > > MAX14001_WRITE_WEN);
> > >
> > > Mixing regmap and non regmap rather defeats the point of having a
> standard
> > > interface. Use regmap_read and regmap_write throughout or not at all.
> >
> > I found it difficult to implement the regmap interface due to the timing
> diagram
> > requirements. The chip select needs to be changed between transfers, which,
> > as far as I know, does not work with regmap. Perhaps, I will consider sticking
> > to the non-regmap approach.
>
> That may be sensible if there are odd requirements or just call regmap_write()
> which will call your max14001_write() anyway and opencode the timing
> requirements etc by multiple remap calls. Obviously benefits of regmap
> reduced
> though so may not be worth bothering unless it is worth using the caching or
> similar.
>
> Jonathan
>
>