Date:   Thu, 20 Jan 2022 18:31:48 +0000
From:   Jonathan Cameron <Jonathan.Cameron@...wei.com>
To:     Cristian Pop <cristian.pop@...log.com>
CC:     <linux-iio@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <jic23@...nel.org>, <devicetree@...r.kernel.org>,
        <robh+dt@...nel.org>
Subject: Re: [PATCH v1 2/2] iio:frequency:admv4420.c: Add support for
 ADMV4420

On Mon, 17 Jan 2022 18:52:47 +0200
Cristian Pop <cristian.pop@...log.com> wrote:

> Add support for K Band Downconverter with Integrated
> Fractional-N PLL and VCO.
> More info:
> https://www.analog.com/en/products/admv4420.html
> 
> Signed-off-by: Cristian Pop <cristian.pop@...log.com>

Hi Cristian,

A few comments inline from a very quick look.

Thanks,

Jonathan


> ---
>  drivers/iio/frequency/Kconfig    |  10 +
>  drivers/iio/frequency/Makefile   |   1 +
>  drivers/iio/frequency/admv4420.c | 412 +++++++++++++++++++++++++++++++
>  3 files changed, 423 insertions(+)
>  create mode 100644 drivers/iio/frequency/admv4420.c
> 
> diff --git a/drivers/iio/frequency/Kconfig b/drivers/iio/frequency/Kconfig
> index b44036f843af..55aa63548c00 100644
> --- a/drivers/iio/frequency/Kconfig
> +++ b/drivers/iio/frequency/Kconfig
> @@ -60,6 +60,16 @@ config ADMV1013
>  	  To compile this driver as a module, choose M here: the
>  	  module will be called admv1013.
>  
> +config ADMV4420
> +	tristate "Analog Devices ADMV4420 K Band Downconverter"
> +	depends on SPI && COMMON_CLK

Why COMMON_CLK?  I can't see any usage.

However, I'm not sure just providing an input frequency is that
sensible as it is likely to be connect to something variable
(to some degree at least).

> +	help
> +	  Say yes here to build support for Analog Devices K Band
> +	  Downconverter with integrated Fractional-N PLL and VCO.
> +
> +	  To compile this driver as a module, choose M here: the
> +	  module will be called admv4420.
> +
>  config ADRF6780
>          tristate "Analog Devices ADRF6780 Microwave Upconverter"
>          depends on SPI
> diff --git a/drivers/iio/frequency/Makefile b/drivers/iio/frequency/Makefile
> index ae6899856c99..782e5baa1630 100644
> --- a/drivers/iio/frequency/Makefile
> +++ b/drivers/iio/frequency/Makefile
> @@ -8,4 +8,5 @@ obj-$(CONFIG_AD9523) += ad9523.o
>  obj-$(CONFIG_ADF4350) += adf4350.o
>  obj-$(CONFIG_ADF4371) += adf4371.o
>  obj-$(CONFIG_ADMV1013) += admv1013.o
> +obj-$(CONFIG_ADMV4420) += admv4420.o
>  obj-$(CONFIG_ADRF6780) += adrf6780.o
> diff --git a/drivers/iio/frequency/admv4420.c b/drivers/iio/frequency/admv4420.c
> new file mode 100644
> index 000000000000..f32039ab2cd3
> --- /dev/null
> +++ b/drivers/iio/frequency/admv4420.c
> @@ -0,0 +1,412 @@
> +// SPDX-License-Identifier: GPL-2.0 OR BSD-2-Clause
> +/*
> + * ADMV4420
> + *
> + * Copyright 2021 Analog Devices Inc.
> + */
> +
> +#include <linux/bitfield.h>
> +#include <linux/iio/iio.h>
> +#include <linux/iio/sysfs.h>
> +#include <linux/module.h>
> +#include <linux/regmap.h>
> +#include <linux/spi/spi.h>
> +
> +/* ADMV4420 Register Map */
> +#define ADMV4420_SPI_CONFIG_1			0x00
> +#define ADMV4420_SPI_CONFIG_2			0x01
> +#define ADMV4420_CHIPTYPE			0x03
> +#define ADMV4420_PRODUCT_ID_L			0x04
> +#define ADMV4420_PRODUCT_ID_H			0x05
> +#define ADMV4420_SCRATCHPAD			0x0A
> +#define ADMV4420_SPI_REV			0x0B
> +#define ADMV4420_ENABLES			0x103
> +#define ADMV4420_SDO_LEVEL			0x108
> +#define ADMV4420_INT_L				0x200
> +#define ADMV4420_INT_H				0x201
> +#define ADMV4420_FRAC_L				0x202
> +#define ADMV4420_FRAC_M				0x203
> +#define ADMV4420_FRAC_H				0x204
> +#define ADMV4420_MOD_L				0x208
> +#define ADMV4420_MOD_M				0x209
> +#define ADMV4420_MOD_H				0x20A
> +#define ADMV4420_R_DIV_L			0x20C
> +#define ADMV4420_R_DIV_H			0x20D
> +#define ADMV4420_REFERENCE			0x20E
> +#define ADMV4420_VCO_DATA_READBACK1		0x211
> +#define ADMV4420_VCO_DATA_READBACK2		0x212
> +#define ADMV4420_PLL_MUX_SEL			0x213
> +#define ADMV4420_LOCK_DETECT			0x214
> +#define ADMV4420_BAND_SELECT			0x215
> +#define ADMV4420_VCO_ALC_TIMEOUT		0x216
> +#define ADMV4420_VCO_MANUAL			0x217
> +#define ADMV4420_ALC				0x219
> +#define ADMV4420_VCO_TIMEOUT1			0x21C
> +#define ADMV4420_VCO_TIMEOUT2			0x21D
> +#define ADMV4420_VCO_BAND_DIV			0x21E
> +#define ADMV4420_VCO_READBACK_SEL		0x21F
> +#define ADMV4420_AUTOCAL			0x226
> +#define ADMV4420_CP_STATE			0x22C
> +#define ADMV4420_CP_BLEED_EN			0x22D
> +#define ADMV4420_CP_CURRENT			0x22E
> +#define ADMV4420_CP_BLEED			0x22F
> +
> +
> +#define ADMV4420_SPI_CONFIG_1_SOFTRESET_	BIT(7)
> +#define ADMV4420_SPI_CONFIG_1_SDOACTIVE_	BIT(4)
> +#define ADMV4420_SPI_CONFIG_1_SDOACTIVE		BIT(3)
> +#define ADMV4420_SPI_CONFIG_1_SOFTRESET		BIT(1)
> +
> +#define ADMV4420_REFERENCE_IN_MODE(x)		(x << 1)
> +#define ADMV4420_REFERENCE_DOUBLER(x)		(x << 2)
> +#define ADMV4420_REFERENCE_DIVIDE_BY_2_MASK	BIT(0)
> +#define ADMV4420_REFERENCE_MODE_MASK		BIT(1)
> +#define ADMV4420_REFERENCE_DOUBLER_MASK		BIT(2)
> +#define ADMV4420_REF_DIVIDER_MAX_VAL		GENMASK(9, 0)
> +#define ADMV4420_N_COUNTER_INT_MAX		GENMASK(15, 0)
> +#define ADMV4420_N_COUNTER_FRAC_MAX		GENMASK(23, 0)
> +#define ADMV4420_N_COUNTER_MOD_MAX		GENMASK(23, 0)
> +
> +#define ADMV4420_INT_L_MASK			GENMASK(7, 0)
> +#define ADMV4420_INT_H_MASK			GENMASK(15, 8)
> +#define ADMV4420_FRAC_L_MASK			GENMASK(7, 0)
> +#define ADMV4420_FRAC_M_MASK			GENMASK(15, 8)
> +#define ADMV4420_FRAC_H_MASK			GENMASK(23, 16)
> +#define ADMV4420_MOD_L_MASK			GENMASK(7, 0)
> +#define ADMV4420_MOD_M_MASK			GENMASK(15, 8)
> +#define ADMV4420_MOD_H_MASK			GENMASK(23, 16)
> +
> +#define ENABLE_PLL				BIT(6)
> +#define ENABLE_LO				BIT(5)
> +#define ENABLE_VCO				BIT(3)
> +#define ENABLE_IFAMP				BIT(2)
> +#define ENABLE_MIXER				BIT(1)
> +#define ENABLE_LNA				BIT(0)
> +
> +#define ADMV4420_SCRATCH_PAD_VAL_1              0xAD
> +#define ADMV4420_SCRATCH_PAD_VAL_2              0xEA
> +
> +#define ADMV4420_REF_FREQ_HZ                    50000000
> +#define MAX_N_COUNTER                           655360UL
> +#define MAX_R_DIVIDER                           1024
> +#define ADMV4420_DEFAULT_LO_FREQ_HZ		16750000000ULL
> +
> +enum admv4420_mux_sel {
> +	ADMV4420_LOW = 0,
> +	ADMV4420_LOCK_DTCT = 1,
> +	ADMV4420_R_COUNTER_PER_2 = 4,
> +	ADMV4420_N_CONUTER_PER_2 = 5,
> +	ADMV4420_HIGH = 8,
> +};
> +
> +struct admv4420_reference_block {
> +	bool doubler_en;
> +	bool divide_by_2_en;
> +	bool ref_single_ended;
> +	u32 divider;
> +};
> +
> +struct admv4420_n_counter {
> +	u32 int_val;
> +	u32 frac_val;
> +	u32 mod_val;
> +	u32 n_counter;
> +};
> +
> +struct admv4420_state {
> +	struct spi_device		*spi;
> +	struct regmap			*regmap;
> +	u64				pfd_freq_hz;
> +	u64				vco_freq_hz;
> +	u64				lo_freq_hz;
> +	struct admv4420_reference_block ref_block;
> +	struct admv4420_n_counter	n_counter;
> +	enum admv4420_mux_sel		mux_sel;
> +	struct mutex			lock;

All locks need a comment saying what exactly their intended scope is.

> +};
> +
> +static const struct regmap_config admv4420_regmap_config = {
> +	.reg_bits = 16,
> +	.val_bits = 8,
> +	.read_flag_mask = BIT(7),
> +};
> +
> +static int admv4420_reg_access(struct iio_dev *indio_dev,
> +			       u32 reg, u32 writeval,
> +			       u32 *readval)
> +{
> +	struct admv4420_state *st = iio_priv(indio_dev);
> +
> +	if (readval)
> +		return regmap_read(st->regmap, reg, readval);
> +	else
> +		return regmap_write(st->regmap, reg, writeval);
> +}
> +
> +static int admv4420_set_n_counter(struct admv4420_state *st, u32 int_val, u32 frac_val, u32 mod_val)

Shorter lines preferred. Under 80 chars unless it significantly affects readability or breaks
up a string we might want to grep for.

> +{
> +	int ret;
> +
> +	ret = regmap_write(st->regmap, ADMV4420_FRAC_H, FIELD_GET(ADMV4420_FRAC_H_MASK, frac_val));

I'm not that keen on doing FIELD_GET for a simple breaking up into 8 bit chunks.
It is a rare occasion where it makes it harder to see what is going on. 

Can't you do a bulk write to set 3 registers in one function call?
Will require a DMA safe buffer but it's probably easier to read than this
repetition


> +	if (ret)
> +		return ret;
> +
> +	ret = regmap_write(st->regmap, ADMV4420_FRAC_M, FIELD_GET(ADMV4420_FRAC_M_MASK, frac_val));
> +	if (ret)
> +		return ret;
> +
> +	ret = regmap_write(st->regmap, ADMV4420_FRAC_L, FIELD_GET(ADMV4420_FRAC_L_MASK, frac_val));
> +	if (ret)
> +		return ret;
> +
> +	ret = regmap_write(st->regmap, ADMV4420_MOD_H, FIELD_GET(ADMV4420_MOD_H_MASK, mod_val));
> +	if (ret)
> +		return ret;
> +
> +	ret = regmap_write(st->regmap, ADMV4420_MOD_M, FIELD_GET(ADMV4420_MOD_M_MASK, mod_val));
> +	if (ret)
> +		return ret;
> +
> +	ret = regmap_write(st->regmap, ADMV4420_MOD_L, FIELD_GET(ADMV4420_MOD_L_MASK, mod_val));
> +	if (ret)
> +		return ret;
> +
> +	ret = regmap_write(st->regmap, ADMV4420_INT_H, FIELD_GET(ADMV4420_INT_H_MASK, int_val));
> +	if (ret)
> +		return ret;
> +
> +	return regmap_write(st->regmap, ADMV4420_INT_L, FIELD_GET(ADMV4420_INT_L_MASK, int_val));
> +}
> +
> +static int admv4420_read_raw(struct iio_dev *indio_dev,
> +			     struct iio_chan_spec const *chan,
> +			     int *val, int *val2, long info)
> +{
> +	struct admv4420_state *st = iio_priv(indio_dev);
> +
> +	switch (info) {
> +	case IIO_CHAN_INFO_FREQUENCY:
> +		*val = div_u64(st->lo_freq_hz, 1000000);
> +		div_u64_rem(st->lo_freq_hz, 1000000, val2);
> +
> +		return IIO_VAL_INT_PLUS_MICRO;
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static const struct iio_info admv4420_info = {
> +	.read_raw = admv4420_read_raw,
> +	.debugfs_reg_access = &admv4420_reg_access,
> +};
> +
> +static const struct iio_chan_spec admv4420_channels[] = {
> +	{
> +		.type = IIO_ALTVOLTAGE,
> +		.output = 0,
> +		.indexed = 1,
> +		.channel = 0,
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_FREQUENCY),
> +	},
> +};
> +
> +static void admv4420_dt_parse(struct admv4420_state *st)
> +{
> +	struct spi_device *spi = st->spi;
> +
> +	device_property_read_u64(&spi->dev, "adi,lo_freq_hz", &st->lo_freq_hz);
> +	st->ref_block.ref_single_ended = of_property_read_bool(spi->dev.of_node,
> +							       "adi,ref_ext_single_ended_en");

Use generic fw properties from include/linux/property.h as
then we get support for other firmware types for free.

> +}
> +
> +static inline uint64_t admv4420_calc_pfd_vco(struct admv4420_state *st)
> +{
> +	return div_u64(st->vco_freq_hz * 10, st->n_counter.n_counter);
> +}
> +
> +static inline uint64_t admv4420_calc_pfd_ref(struct admv4420_state *st)
> +{
> +	uint64_t tmp;
> +
> +	tmp = ADMV4420_REF_FREQ_HZ * (st->ref_block.doubler_en ? 2 : 1);
> +	return div_u64(tmp, st->ref_block.divider * (st->ref_block.divide_by_2_en ? 2 : 1));

Pull that ternary operating out on it's own line. There is too much going on in
one statement to make it easy to read!

> +}
> +
> +static int admv4420_calc_parameters(struct admv4420_state *st)
> +{
> +	u64 pfd_ref, pfd_vco;
> +	bool sol_found = false;
> +
> +	st->ref_block.doubler_en = false;
> +	st->ref_block.divide_by_2_en = false;
> +	st->vco_freq_hz = div_u64(st->lo_freq_hz, 2);
> +
> +	for (st->ref_block.divider = 1; st->ref_block.divider < MAX_R_DIVIDER;
> +	    st->ref_block.divider++) {
> +		pfd_ref = admv4420_calc_pfd_ref(st);
> +		for (st->n_counter.n_counter = 1; st->n_counter.n_counter < MAX_N_COUNTER;
> +		    st->n_counter.n_counter++) {
> +			pfd_vco = admv4420_calc_pfd_vco(st);
> +			if (pfd_ref == pfd_vco) {
> +				sol_found = true;
> +				break;
> +			}
> +		}
> +
> +		if (sol_found)
> +			break;
> +
> +		st->n_counter.n_counter = 1;
> +	}
> +	if (!sol_found)
> +		return -1;
> +
> +	st->n_counter.int_val = div_u64_rem(st->n_counter.n_counter, 10, &st->n_counter.frac_val);
> +	st->n_counter.mod_val = 1;
> +
> +	return 0;
> +}
> +
> +static int admv4420_setup(struct iio_dev *indio_dev)
> +{
> +	struct admv4420_state *st = iio_priv(indio_dev);
> +	u32 val = 0;

This will always be set before use.  If you are seeing a compiler warning then fine to leave
it here but perhaps add a comment so no one 'cleans it up'.

> +	int ret;
> +
> +	ret = regmap_write(st->regmap, ADMV4420_SPI_CONFIG_1,
> +			   ADMV4420_SPI_CONFIG_1_SOFTRESET_ | ADMV4420_SPI_CONFIG_1_SOFTRESET);

In general try to keep below 80 chars where it is easy to do like here.

> +	if (ret)
> +		return ret;
> +
> +	ret = regmap_write(st->regmap, ADMV4420_SPI_CONFIG_1,
> +			   ADMV4420_SPI_CONFIG_1_SDOACTIVE_ | ADMV4420_SPI_CONFIG_1_SDOACTIVE);
> +	if (ret)
> +		return ret;
> +
> +	ret = regmap_write(st->regmap, ADMV4420_SCRATCHPAD, ADMV4420_SCRATCH_PAD_VAL_1);
> +	if (ret)
> +		return ret;
> +
> +	ret = regmap_read(st->regmap, ADMV4420_SCRATCHPAD, &val);
> +	if (ret)
> +		return ret;
> +
> +	if (val != ADMV4420_SCRATCH_PAD_VAL_1) {
> +		dev_err(indio_dev->dev.parent, "Failed ADMV4420 to read/write scratchpad %x ", val);
> +		return -EIO;
> +	}
> +
> +	ret = regmap_write(st->regmap, ADMV4420_SCRATCHPAD, ADMV4420_SCRATCH_PAD_VAL_2);
> +	if (ret)
> +		return ret;
> +
> +	ret = regmap_read(st->regmap, ADMV4420_SCRATCHPAD, &val);
> +	if (ret)
> +		return ret;
> +
> +	if (val != ADMV4420_SCRATCH_PAD_VAL_2) {
> +		dev_err(indio_dev->dev.parent, "Failed to read/write scratchpad %x ", val);
> +		return -EIO;
> +	}
> +
> +	st->mux_sel = ADMV4420_LOCK_DTCT;
> +	st->lo_freq_hz = ADMV4420_DEFAULT_LO_FREQ_HZ;
> +
> +	admv4420_dt_parse(st);

I doubt this needs to be dt specific so _fw_parse()

> +
> +	ret = admv4420_calc_parameters(st);
> +	if (ret) {
> +		dev_err(indio_dev->dev.parent, "Failed calc parameters for %lld ", st->vco_freq_hz);
> +		return ret;
> +	}
> +
> +	ret = regmap_write(st->regmap, ADMV4420_R_DIV_L,
> +			   FIELD_GET(0xFF, st->ref_block.divider));
> +	if (ret)
> +		return ret;
> +
> +	ret = regmap_write(st->regmap, ADMV4420_R_DIV_H,
> +			   FIELD_GET(0xFF00, st->ref_block.divider));
> +	if (ret)
> +		return ret;
> +
> +	ret = regmap_write(st->regmap, ADMV4420_REFERENCE,
> +			   st->ref_block.divide_by_2_en |
> +			   ADMV4420_REFERENCE_IN_MODE(st->ref_block.ref_single_ended) |
> +			   ADMV4420_REFERENCE_DOUBLER(st->ref_block.doubler_en));
> +	if (ret)
> +		return ret;
> +
> +	ret = admv4420_set_n_counter(st, st->n_counter.int_val, st->n_counter.frac_val, st->n_counter.mod_val);
> +	if (ret)
> +		return ret;
> +
> +	ret = regmap_write(st->regmap, ADMV4420_PLL_MUX_SEL, st->mux_sel);
> +	if (ret)
> +		return ret;
> +
> +	ret = regmap_write(st->regmap, ADMV4420_ENABLES, ENABLE_PLL | ENABLE_LO | ENABLE_VCO |
> +			   ENABLE_IFAMP | ENABLE_MIXER | ENABLE_LNA);

return regmap_write()

> +	if (ret)
> +		return ret;
> +
> +	return 0;
> +}
> +
> +static int admv4420_probe(struct spi_device *spi)
> +{
> +	struct iio_dev *indio_dev;
> +	struct admv4420_state *st;
> +	struct regmap *regmap;
> +	int ret;
> +
> +	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*st));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	regmap = devm_regmap_init_spi(spi, &admv4420_regmap_config);
> +	if (IS_ERR(regmap)) {
> +		dev_err(&spi->dev, "Error  ADMV4420 initializing spi regmap: %ld\n",
> +			PTR_ERR(regmap));
> +		return PTR_ERR(regmap);

For probe errors, it is often easier to just use dev_err_probe() for all of them
whether or not they can defer.


> +	}
> +
> +	st = iio_priv(indio_dev);
> +	st->spi = spi;
> +	st->regmap = regmap;
> +	mutex_init(&st->lock);
> +
> +	indio_dev->dev.parent = &spi->dev;

We set that automatically in devm_iio_device_alloc() as it's almost always
the same value as passed in as dev to that function and in rare case
where it is different we can override. Here they are the same.

> +	indio_dev->name = "admv4420";
> +	indio_dev->info = &admv4420_info;
> +	indio_dev->channels = admv4420_channels;
> +	indio_dev->num_channels = ARRAY_SIZE(admv4420_channels);
> +
> +	ret = admv4420_setup(indio_dev);
> +	if (ret) {
> +		dev_err(&spi->dev, "Setup ADMV4420 failed (%d)\n", ret);
> +		return ret;
> +	}
> +
> +	return devm_iio_device_register(&spi->dev, indio_dev);
> +}
> +

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