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Date: Fri, 12 Dec 2014 16:58:04 +0100
From: Nikolaus Schulz <nikolaus.schulz@...onic-design.de>
To: Hartmut Knaack <knaack.h@....de>
Cc: Jonathan Cameron <jic23@...nel.org>,
Lars-Peter Clausen <lars@...afoo.de>,
Peter Meerwald <pmeerw@...erw.net>,
Grant Likely <grant.likely@...aro.org>,
Rob Herring <robh+dt@...nel.org>,
Michael Welling <mwelling@...e.org>,
Philippe Reynes <tremyfr@...oo.fr>,
linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org,
devicetree@...r.kernel.org,
Alban Bedel <alban.bedel@...onic-design.de>
Subject: Re: [PATCH v2 2/2] iio: add driver for the TI DAC8554
On Sat, Dec 06, 2014 at 12:36:19PM +0100, Hartmut Knaack wrote:
> Nikolaus Schulz schrieb am 24.11.2014 um 20:50:
> > The TI DAC8554 is a quad-channel Digital-to-Analog Converter with an SPI
> > interface.
> >
> > Changes in v2:
> > * Use DMA-safe buffer for SPI transfer
> > * Normalize powerdown_mode name "hi-z" to "three_state" as per
> > ABI/testing/sysfs-bus-iio
> > * Register device late in probe function
> > * Avoid powerdown broadcast update, which touches all DAC on the bus
> There are a few issues left, please see my comments inline.
> >
> > Signed-off-by: Nikolaus Schulz <nikolaus.schulz@...onic-design.de>
> > ---
> > drivers/iio/dac/Kconfig | 10 ++
> > drivers/iio/dac/Makefile | 1 +
> > drivers/iio/dac/ti-dac8554.c | 374 +++++++++++++++++++++++++++++++++++++++++++
> > 3 files changed, 385 insertions(+)
> > create mode 100644 drivers/iio/dac/ti-dac8554.c
[...]
> > diff --git a/drivers/iio/dac/ti-dac8554.c b/drivers/iio/dac/ti-dac8554.c
> > new file mode 100644
> > index 0000000..fca751f
> > --- /dev/null
> > +++ b/drivers/iio/dac/ti-dac8554.c
> > @@ -0,0 +1,374 @@
> > +/*
> > + * TI DAC8554 Digital to Analog Converter SPI driver
> > + *
> > + * Copyright (C) 2014 Avionic Design GmbH
> > + *
> > + * Based on ad5446r_spi.c
> > + * Copyright (C) 2010,2011 Analog Devices Inc.
> > + *
> > + * This program is free software; you can redistribute it and/or modify
> > + * it under the terms of the GNU General Public License version 2 as
> > + * published by the Free Software Foundation.
> > + */
> > +
> > +#include <linux/spi/spi.h>
> > +#include <linux/regulator/consumer.h>
> > +#include <linux/module.h>
> > +#include <linux/iio/iio.h>
> > +#include <linux/of.h>
> > +
> > +#define DAC8554_DRIVERNAME "ti-dac8554"
> > +#define DAC8554_DAC_CHANNELS 4
> > +
> > +/* Load commands */
> > +#define DAC8554_CMD_STORE_DAC_N 0x0
> > +#define DAC8554_CMD_UPDATE_DAC_N 0x1
> > +#define DAC8554_CMD_STORE_DAC_N_UPDATE_ALL 0x2
> > +#define DAC8554_CMD_UPDATE_BROADCAST 0x3
> > +
> > +#define DAC8554_BROADCAST_USE_SRDATA 0x2
> Add a blank line here.
Fixed.
> > +/* Powerdown modes (ORed PD1|PD2 bits) */
> It took my some time to figure out ORed. I think you could drop it and just
> mention (PD1 | PD2 bits).
Agreed, and fixed.
> > +#define DAC8554_PWRDN_HIZ 0x0
> > +#define DAC8554_PWRDN_1K 0x1
> > +#define DAC8554_PWRDN_100K 0x2
> > +
> > +#define DAC8554_PWRDN_TO_SR(mode) (BIT(16) | (mode) << 14)
> > +
> > +/**
> > + * struct dac8554_state - driver instance specific data
> > + * @spi: spi_device
> SPI device?
Yes, fixed.
> > + * @reg: supply regulator
> > + * @addr: two-bit chip address
> > + * @vref_mv: reference voltage in millivolt
> > + * @val DAC/channel data
> DAC channel data?
"channel data" will do, actually.
> > + * @powerdown channel powerdown flag
> > + * @powerdown_mode channel powerdown mode
> > + * @xfer SPI transfer buffer
> Half of the comments are with colon, the other half are missing it.
Fixed.
> > + */
> > +struct dac8554_state {
> > + struct spi_device *spi;
> > + struct regulator *reg;
> > + unsigned addr;
> > + unsigned vref_mv;
> > + u16 val[DAC8554_DAC_CHANNELS];
> > + bool powerdown[DAC8554_DAC_CHANNELS];
> > + u8 powerdown_mode[DAC8554_DAC_CHANNELS];
> > +
> > + /*
> > + * DMA (thus cache coherency maintenance) requires the
> > + * transfer buffers to live in their own cache lines.
> > + */
> > + u8 xfer[3] ____cacheline_aligned;
> > +};
> > +
> > +static int dac8554_spi_write(struct dac8554_state *st,
> > + unsigned cmd,
> > + unsigned chan_addr,
> > + unsigned val)
> > +{
> > + u32 data;
> > +
> > + /*
> > + * The input shift register is 24 bits wide. The 8 MSB are
> > + * control bits, followed by 16 data bits.
> > + * The first two bits A1 and A0 address a DAC8554 chip.
> > + * The next two are the command bits, LD1 and LD0.
> > + * After a don't-care-bit, the next two bits select the channel.
> > + * The final control bit PD0 is a flag signalling if the data
> > + * bits encode a powerdown mode. We merge PD0 with the adjacent
> > + * data bits.
> > + */
> > +
> > + if (cmd > 3 || chan_addr > 3 ||
> > + (val > 0xffff && (val & ~DAC8554_PWRDN_TO_SR(3))))
> > + return -EINVAL;
> > +
> > + data = (st->addr << 22) | (cmd << 20) | (chan_addr << 17) | val;
> Could be more readable by using definition for the magic shifts, or macros.
Hmm. The magic is all concentrated at this place, and the variable names
tell the story, so I figured that's ok. But, why not: fixed.
> > + st->xfer[0] = data >> 16;
> > + st->xfer[1] = data >> 8;
> > + st->xfer[2] = data;
> > +
> > + return spi_write(st->spi, st->xfer, sizeof(st->xfer));
> > +}
> > +
> > +static int dac8554_read_raw(struct iio_dev *indio_dev,
> > + struct iio_chan_spec const *chan,
> > + int *val,
> > + int *val2,
> > + long m)
> Commonly, m is called mask (like you do in _write_raw).
Ah yes. Fixed.
> > +{
> > + struct dac8554_state *st = iio_priv(indio_dev);
> > +
> > + switch (m) {
> > + case IIO_CHAN_INFO_RAW:
> > + *val = st->val[chan->address];
> > + return IIO_VAL_INT;
> > + case IIO_CHAN_INFO_SCALE:
> > + *val = st->vref_mv;
> > + *val2 = 16;
> > + return IIO_VAL_FRACTIONAL_LOG2;
> > + }
> > + return -EINVAL;
> > +}
> > +
> > +static int dac8554_write_raw(struct iio_dev *indio_dev,
> > + struct iio_chan_spec const *chan,
> > + int val,
> > + int val2,
> > + long mask)
> > +{
> > + struct dac8554_state *st = iio_priv(indio_dev);
> > + int err;
> > +
> > + switch (mask) {
> > + case IIO_CHAN_INFO_RAW:
> > + if (val > 0xffff || val < 0)
> > + return -EINVAL;
> > +
> > + err = dac8554_spi_write(st, DAC8554_CMD_UPDATE_DAC_N,
> > + chan->address, val);
> > + if (err)
> > + return err;
> > +
> > + st->val[chan->address] = val;
> > +
> > + /* By hw design, DAC updates automatically trigger powerup. */
> > + st->powerdown[chan->address] = false;
> > +
> > + return 0;
> > +
> > + default:
> > + return -EINVAL;
> > + }
> > +}
> > +
> > +static int dac8554_get_powerdown_mode(struct iio_dev *indio_dev,
> > + const struct iio_chan_spec *chan)
> > +{
> > + struct dac8554_state *st = iio_priv(indio_dev);
> > +
> > + return st->powerdown_mode[chan->address];
> > +}
> > +
> > +static int dac8554_set_powerdown_mode(struct iio_dev *indio_dev,
> > + const struct iio_chan_spec *chan,
> > + unsigned int mode)
> > +{
> > + struct dac8554_state *st = iio_priv(indio_dev);
> > +
> > + st->powerdown_mode[chan->address] = mode;
> > +
> > + return 0;
> > +}
> > +
> > +static ssize_t dac8554_read_dac_powerdown(struct iio_dev *indio_dev,
> > + uintptr_t private,
> > + const struct iio_chan_spec *chan,
> > + char *buf)
> > +{
> > + struct dac8554_state *st = iio_priv(indio_dev);
> > +
> > + return sprintf(buf, "%d\n", st->powerdown[chan->address]);
> > +}
> > +
> > +static ssize_t dac8554_write_dac_powerdown(struct iio_dev *indio_dev,
> > + uintptr_t private,
> > + const struct iio_chan_spec *chan,
> > + const char *buf,
> > + size_t len)
> > +{
> > + bool powerdown;
> > + int ret;
> > + struct dac8554_state *st = iio_priv(indio_dev);
> > + u8 powerdown_mode;
> > +
> > + ret = strtobool(buf, &powerdown);
> > + if (ret)
> > + return ret;
> > +
> > + st->powerdown[chan->address] = powerdown;
> > +
> > + if (powerdown) {
> > + powerdown_mode = st->powerdown_mode[chan->address];
> > + ret = dac8554_spi_write(st,
> > + DAC8554_CMD_UPDATE_DAC_N,
> > + chan->address,
> > + DAC8554_PWRDN_TO_SR(powerdown_mode));
> The parameters sill fit on line even with proper indentation.
Fixed.
> > + } else {
> > + /* Load DAC with cached value. This triggers a powerup. */
> > + ret = dac8554_spi_write(st,
> > + DAC8554_CMD_UPDATE_DAC_N,
> > + chan->address,
> > + st->val[chan->address]);
> Same here with indentation.
Fixed.
> > + }
> > +
> > + if (ret)
> > + return ret;
> > +
> > + return len;
> Just: return (ret) ? ret : len;
I think avoiding the ternary operator makes the code more readable, and
it separates the error path from normal operation. So I would prefer to
keep it that way.
> > +}
> > +
> > +static int dac8554_powerdown(struct dac8554_state *st,
> > + u8 powerdown_mode)
> > +{
> > + int chan, cmd, ret;
> > +
> > + for (chan = DAC8554_DAC_CHANNELS-1; chan >= 0; --chan) {
> Please mind spaces around operators.
Fixed.
> > + cmd = chan ? DAC8554_CMD_STORE_DAC_N
> > + : DAC8554_CMD_STORE_DAC_N_UPDATE_ALL;
> > + ret = dac8554_spi_write(st, cmd, chan,
> > + DAC8554_PWRDN_TO_SR(powerdown_mode));
> > + if (ret)
> > + return ret;
> > + }
> > +
> > + memset(st->powerdown_mode, powerdown_mode, sizeof(st->powerdown_mode));
> > + memset(st->powerdown, true, sizeof(st->powerdown));
> > +
> > + return 0;
> > +}
> > +
> > +static const struct iio_info dac8554_info = {
> > + .write_raw = dac8554_write_raw,
> > + .read_raw = dac8554_read_raw,
> > + .driver_module = THIS_MODULE,
> > +};
> > +
> > +static const char * const dac8554_powerdown_modes[] = {
> > + "three_state",
> > + "1kohm_to_gnd",
> > + "100kohm_to_gnd"
> > +};
> > +
> > +static const struct iio_enum dac8854_powerdown_mode_enum = {
> > + .items = dac8554_powerdown_modes,
> > + .num_items = ARRAY_SIZE(dac8554_powerdown_modes),
> > + .get = dac8554_get_powerdown_mode,
> > + .set = dac8554_set_powerdown_mode,
> > +};
> > +
> > +static const struct iio_chan_spec_ext_info dac8554_ext_info[] = {
> > + {
> > + .name = "powerdown",
> > + .read = dac8554_read_dac_powerdown,
> > + .write = dac8554_write_dac_powerdown,
> > + .shared = IIO_SEPARATE,
> > + },
> > + IIO_ENUM("powerdown_mode", IIO_SEPARATE,
> > + &dac8854_powerdown_mode_enum),
> > + IIO_ENUM_AVAILABLE("powerdown_mode", &dac8854_powerdown_mode_enum),
> > + { },
> > +};
> > +
> > +#define DAC8554_CHANNEL(chan) { \
> > + .type = IIO_VOLTAGE, \
> > + .indexed = 1, \
> > + .output = 1, \
> > + .channel = (chan), \
> > + .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
> > + .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
> > + .address = (chan), \
> > + .ext_info = dac8554_ext_info, \
> > +}
> > +const struct iio_chan_spec dac8554_channels[] = {
> > + DAC8554_CHANNEL(0),
> > + DAC8554_CHANNEL(1),
> > + DAC8554_CHANNEL(2),
> > + DAC8554_CHANNEL(3),
> > +};
> > +#undef DAC8554_CHANNEL
> > +
> > +static int dac8554_probe(struct spi_device *spi)
> > +{
> > + struct dac8554_state *st;
> > + struct iio_dev *indio_dev;
> > + int ret, voltage_uv;
> > + u32 addr;
> > +
> > + indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*st));
> > + if (!indio_dev)
> > + return -ENOMEM;
> > +
> > + indio_dev->dev.parent = &spi->dev;
> > + indio_dev->name = DAC8554_DRIVERNAME;
> > + indio_dev->info = &dac8554_info;
> > + indio_dev->modes = INDIO_DIRECT_MODE;
> > + indio_dev->channels = dac8554_channels;
> > + indio_dev->num_channels = ARRAY_SIZE(dac8554_channels);
> > +
> > + spi_set_drvdata(spi, indio_dev);
> > +
> > + st = iio_priv(indio_dev);
> > +
> > + if (!spi->dev.of_node) {
> > + dev_err(&spi->dev, "missing OF node");
> > + return -ENODEV;
> > + }
> > + ret = of_property_read_u32(spi->dev.of_node, "address", &addr);
> > + if (ret || addr < 0 || addr > 2) {
> > + dev_err(&spi->dev, "no or invalid chip address");
> > + return -ENODEV;
> > + }
> > +
> > + st->spi = spi;
> > + st->addr = addr;
> > +
> According to your DT bindings, the regulator from property "vref-supply" should
> be used. This is missing here.
Uhm, it's right below, no?
> > + st->reg = devm_regulator_get(&spi->dev, "vref");
> > + if (IS_ERR(st->reg))
> > + return PTR_ERR(st->reg);
> > +
> > + ret = regulator_enable(st->reg);
> > + if (ret)
> > + return ret;
> > +
> > + voltage_uv = regulator_get_voltage(st->reg);
> > + if (voltage_uv < 0)
> > + goto error_disable_reg;
> Missing ret = voltage_uv before goto. Or just drop voltage_uv completely and use ret instead.
Fixed.
> > + st->vref_mv = voltage_uv / 1000;
> How hard do you want to depend on a voltage regulator? Doing regulator_get_voltage()
> could even be called dynamically in _read_raw(), making a real regulator optional.
Hmm. I understand that the DAC voltage input may not be provided by a
regulator, but is that a common scenario? No other DAC driver I looked
at handles that case, they all consider it an error if the regulator is
absent.
> > +
> > + ret = dac8554_powerdown(st, DAC8554_PWRDN_100K);
> > + if (ret)
> > + goto error_disable_reg;
> > +
> > + ret = iio_device_register(indio_dev);
> > + if (ret)
> > + goto error_disable_reg;
> > +
> > + return 0;
> > +
> > +error_disable_reg:
> > + regulator_disable(st->reg);
> > + return ret;
> > +}
> > +
> > +static int dac8554_remove(struct spi_device *spi)
> > +{
> > + struct iio_dev *indio_dev = spi_get_drvdata(spi);
> > + struct dac8554_state *st = iio_priv(indio_dev);
> > +
> > + iio_device_unregister(indio_dev);
> > + regulator_disable(st->reg);
> > +
> > + return 0;
> > +}
> > +
> > +static const struct of_device_id dac8554_of_match[] = {
> > + { .compatible = "ti,dac8554" },
> > + { }
> > +};
> > +MODULE_DEVICE_TABLE(of, dac8554_of_match);
> > +
> > +static struct spi_driver dac8554_driver = {
> > + .driver = {
> > + .name = DAC8554_DRIVERNAME,
> > + .owner = THIS_MODULE,
> > + .of_match_table = dac8554_of_match,
> > + },
> > + .probe = dac8554_probe,
> > + .remove = dac8554_remove,
> > +};
> > +module_spi_driver(dac8554_driver);
> > +
> > +MODULE_AUTHOR("Nikolaus Schulz <nikolaus.schulz@...onic-design.de>");
> > +MODULE_DESCRIPTION("Texas Instruments DAC8554 SPI driver");
> > +MODULE_LICENSE("GPL v2");
Thanks for the review!
Nikolaus
--
Avionic Design GmbH
Nikolaus Schulz
Wragekamp 10
D-22397 Hamburg
Germany
Tel.: +49 40 88187-163
Fax: +49 40 88187-150
Email: nikolaus.schulz@...onic-design.de
Avionic Design GmbH
Amtsgericht Hamburg HRB 82598
Geschäftsführung: Cornelis Broers
Ust.-Ident-Nr.: DE813378254
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