Re: [PATCH v2] iio:dac:ti-dac7612: Add driver for Texas Instruments DAC7612
From: Ricardo Ribalda Delgado
Date: Sat Jan 26 2019 - 16:35:14 EST
HI Jonathan
Thanks for your review. I will make the changes and send it back to
you after testing it on Monday on real hardware.
Until then I have pushed my changes to
https://github.com/ribalda/linux/tree/ribalda-iio-v3 in case you want
to see it before I send it to the list.
(I am still missing the dt-bindings)
Some comments inline.
Best regards!
On Sat, Jan 26, 2019 at 9:42 PM Jonathan Cameron <jic23@xxxxxxxxxx> wrote:
>
> On Fri, 25 Jan 2019 11:00:55 +0100
> Ricardo Ribalda Delgado <ricardo@xxxxxxxxxxx> wrote:
>
> > It is a driver for Texas Instruments Dual, 12-Bit Serial Input
> > Digital-to-Analog Converter.
> >
> > Datasheet of this chip:
> > http://www.ti.com/lit/ds/sbas106/sbas106.pdf
> >
> > Signed-off-by: Ricardo Ribalda Delgado <ricardo@xxxxxxxxxxx>
> Hi Ricardo,
>
> Various bits and pieces inline.
>
> Jonathan
>
> > ---
> >
> > v2: Fix range
> > MAINTAINERS | 6 ++
> > drivers/iio/dac/Kconfig | 10 +++
> > drivers/iio/dac/Makefile | 1 +
> > drivers/iio/dac/ti-dac7612.c | 169 +++++++++++++++++++++++++++++++++++
> > 4 files changed, 186 insertions(+)
> > create mode 100644 drivers/iio/dac/ti-dac7612.c
> >
> > diff --git a/MAINTAINERS b/MAINTAINERS
> > index d039f66a5cef..30ba5435906b 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -14877,6 +14877,12 @@ F: Documentation/devicetree/bindings/clock/ti,sci-clk.txt
> > F: drivers/clk/keystone/sci-clk.c
> > F: drivers/reset/reset-ti-sci.c
> >
> > +Texas Instruments' DAC7612 DAC Driver
> > +M: Ricardo Ribalda <ricardo@xxxxxxxxxxx>
> > +L: linux-iio@xxxxxxxxxxxxxxx
> > +S: Supported
> > +F: drivers/iio/dac/ti-dac7612.c
> > +
> > THANKO'S RAREMONO AM/FM/SW RADIO RECEIVER USB DRIVER
> > M: Hans Verkuil <hverkuil@xxxxxxxxx>
> > L: linux-media@xxxxxxxxxxxxxxx
> > diff --git a/drivers/iio/dac/Kconfig b/drivers/iio/dac/Kconfig
> > index f28daf67db6a..fbef9107acad 100644
> > --- a/drivers/iio/dac/Kconfig
> > +++ b/drivers/iio/dac/Kconfig
> > @@ -375,6 +375,16 @@ config TI_DAC7311
> >
> > If compiled as a module, it will be called ti-dac7311.
> >
> > +config TI_DAC7612
> > + tristate "Texas Instruments 12-bit 2-channel DAC driver"
> > + depends on SPI_MASTER && GPIOLIB
> > + help
> > + Driver for the Texas Instruments DAC7612, DAC7612U, DAC7612UB
> > + The driver hand drive the load pin automatically, otherwise
> > + it needs to be toggled manually.
>
> Given the driver doesn't load without that pin, do we need to give
> the otherwise? I would drop this comment entirely.
I am probing the gpio with devm_gpiod_get_optional() so the driver can
load without the pin
>
> > +
> > + If compiled as a module, it will be called ti-dac7612.
> > +
> > config VF610_DAC
> > tristate "Vybrid vf610 DAC driver"
> > depends on OF
> > diff --git a/drivers/iio/dac/Makefile b/drivers/iio/dac/Makefile
> > index f0a37c93de8e..1369fa1d2f0e 100644
> > --- a/drivers/iio/dac/Makefile
> > +++ b/drivers/iio/dac/Makefile
> > @@ -41,4 +41,5 @@ obj-$(CONFIG_STM32_DAC) += stm32-dac.o
> > obj-$(CONFIG_TI_DAC082S085) += ti-dac082s085.o
> > obj-$(CONFIG_TI_DAC5571) += ti-dac5571.o
> > obj-$(CONFIG_TI_DAC7311) += ti-dac7311.o
> > +obj-$(CONFIG_TI_DAC7612) += ti-dac7612.o
> > obj-$(CONFIG_VF610_DAC) += vf610_dac.o
> > diff --git a/drivers/iio/dac/ti-dac7612.c b/drivers/iio/dac/ti-dac7612.c
> > new file mode 100644
> > index 000000000000..278406f69e0c
> > --- /dev/null
> > +++ b/drivers/iio/dac/ti-dac7612.c
> > @@ -0,0 +1,169 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * DAC7612 Dual, 12-Bit Serial input Digital-to-Analog Converter
> > + *
> > + * Copyright 2019 Qtechnology A/S
> > + * 2019 Ricardo Ribalda <ricardo@xxxxxxxxxxx>
> > + *
> > + * Licensed under the GPL-2.
> > + */
> > +#include <linux/kernel.h>
> > +#include <linux/module.h>
> > +#include <linux/spi/spi.h>
> > +#include <linux/gpio/consumer.h>
> > +#include <linux/iio/iio.h>
> > +
> > +#define NUM_CHANS 2
> > +#define RESOLUTION 12
> Please prefix any naming that is generic like this with
> the driver name. Avoids potential redefined clashes in the future.
> Where they are 'real numbers' rather than Magic numbers I would
> generally look at using the actual number rather than a define.
>
> > +
> > +struct dac7612 {
> > + struct spi_device *spi;
> > + struct gpio_desc *nld;
> > + uint16_t cache[NUM_CHANS];
> > +};
> > +
> > +static int dac7612_cmd_single(struct dac7612 *priv, int channel, u16 val)
> > +{
> > + uint8_t buffer[2];
> > + int ret;
> > +
> > + if (channel >= NUM_CHANS)
> Is there any way this can happen? Seems a little over paranoid.
> > + return -EINVAL;
> > +
> > + buffer[0] = BIT(5) | (channel << 4) | (val >> 8);
> BIT(5) is a magic number so should probably come from a define
> as should the shifts of the other parts.
>
> > + buffer[1] = val & 0xff;
> > +
> > + priv->cache[channel] = val;
> > +
> > + ret = spi_write(priv->spi, buffer, sizeof(buffer));
>
> spi write can potentially do a dma transfer so it needs
> a dma safe buffer. This one isn't as it is on the stack.
> Given it is a moderately fast path, best option is to put the
> buffer in priv and use the __cacheline_aligned trick (plus the
> fact private data is already cacheline aligned) to get it into
> it's own cacheline. Wofram Sang's OSS talk on i2c dma is a good
> tutorial on this and is on youtube if you have time.
>
> https://www.youtube.com/watch?v=JDwaMClvV-s
>
> > + if (ret)
> > + return ret;
> > +
> > + gpiod_set_value(priv->nld, 0);
> > + gpiod_set_value(priv->nld, 1);
> > +
> > + return 0;
> > +}
> > +
> > +#define dac7612_CHANNEL(chan, name) { \
> > + .type = IIO_VOLTAGE, \
> > + .channel = (chan), \
> > + .address = (chan), \
> Not used, so don't set it.
>
> > + .indexed = true, \
> These are bit fields, so whilst this works, = 1 is more conventional.
>
> > + .output = true, \
> > + .datasheet_name = name, \
> > + .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
> > + .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
> > + .scan_type = { \
> > + .sign = 'u', \
> > + .realbits = RESOLUTION, \
> > + .storagebits = RESOLUTION, \
> No need to provide scan_type as we don't have buffered output in
> mainline. Also this would be wrong as storagebits needs to be
> 8/16/32/64 etc.
>
> Would prefer a straight forward value like RESOLUTION was just
> expressed as a number.
>
> > + }, \
> > +}
> > +
> > +static const struct iio_chan_spec dac7612_channels[] = {
> > + dac7612_CHANNEL(0, "OUTA"),
> > + dac7612_CHANNEL(1, "OUTB"),
> > +};
> > +
> > +static int dac7612_read_raw(struct iio_dev *iio_dev,
> > + const struct iio_chan_spec *chan,
> > + int *val, int *val2, long mask)
> > +{
> > + struct dac7612 *priv;
> > +
> > + switch (mask) {
> > + case IIO_CHAN_INFO_RAW:
> > + priv = iio_priv(iio_dev);
> > + *val = priv->cache[chan->channel];
> > + return IIO_VAL_INT;
> > +
> > + case IIO_CHAN_INFO_SCALE:
> > + *val = 1000000;
>
> This makes me wonder. The units of voltage are millivolts, so is
> raw value * 1000000 = value in mv?
I tried using IIO_VAL_FRACTIONAL, with val = 1 and val2=1000000, and
it only returned -EINVAL.
Then I discovered the PLUS_MICRO and I want to remember that cating
the range sysfs file returned:
0,000001, but I will try again on Monday.
>
> That would make this a very high voltage device.
> See Documentation/ABI/testing/sysfs-bus-iio* for
> IIO ABI documentation.
>
> > + return IIO_VAL_INT_PLUS_MICRO;
> > +
> > + default:
> > + return -EINVAL;
> > + }
> > +}
> > +
> > +static int dac7612_write_raw(struct iio_dev *iio_dev,
> > + const struct iio_chan_spec *chan,
> > + int val, int val2, long mask)
> > +{
> > + struct dac7612 *priv;
>
> struct dac7612 *priv = iio_priv(iio_dev);
>
> (it's just macro magic to get the right point so normally considered
> fine to be called like this).
>
>
> > + int ret;
> > +
> > + if (mask != IIO_CHAN_INFO_RAW)
> > + return -EINVAL;
> > +
> > + if ((val >= BIT(RESOLUTION)) || val < 0)
> > + return -EINVAL;
>
> As not providing a write_fmt function (which is fine)
> should also sanity check that val2 is 0.
>
> > +
> > + priv = iio_priv(iio_dev);
> > + if (val == priv->cache[chan->channel])
> > + return 0;
> > +
> > + mutex_lock(&iio_dev->mlock);
> > + ret = dac7612_cmd_single(priv, chan->channel, val);
> > + mutex_unlock(&iio_dev->mlock);
> > +
> > + return ret;
> > +}
> > +
> > +static const struct iio_info dac7612_info = {
> > + .read_raw = dac7612_read_raw,
> > + .write_raw = dac7612_write_raw,
> > +};
> > +
> > +static int dac7612_probe(struct spi_device *spi)
> > +{
> > + struct iio_dev *iio_dev;
> > + struct dac7612 *priv;
> > + int i;
> > + int ret;
> > +
> > + iio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*priv));
> > + if (!iio_dev)
> > + return -ENOMEM;
> > +
> > + priv = iio_priv(iio_dev);
> > + priv->nld = devm_gpiod_get_optional(&spi->dev, "nLD", GPIOD_OUT_HIGH);
>
> This isn't a particularly standard gpio name. Hence this driver definitely
> needs a DT binding doc (remember to cc dt list and maintainers). Also
> this should almost certainly be prefixed with a vendor prefix.
>
> It's also not the name I'm seeing on the datasheet, so needs some justifying
> comments.
>
> > + if (IS_ERR(priv->nld))
> > + return PTR_ERR(priv->nld);
> > + priv->spi = spi;
> > + spi_set_drvdata(spi, iio_dev);
> > + iio_dev->dev.parent = &spi->dev;
> > + iio_dev->info = &dac7612_info;
> > + iio_dev->modes = INDIO_DIRECT_MODE;
> > + iio_dev->channels = dac7612_channels;
> > + iio_dev->num_channels = NUM_CHANS;
> ARRAY_SIZE.
> > + iio_dev->name = spi_get_device_id(spi)->name;
> > +
> > + for (i = 0; i < NUM_CHANS; i++) {
> ARRAY_SIZE
> > + ret = dac7612_cmd_single(priv, i, 0);
> > + if (ret)
> > + return ret;
> > + }
> > +
> > + return devm_iio_device_register(&spi->dev, iio_dev);
> > +}
> > +
> > +static const struct spi_device_id dac7612_id[] = {
> > + {"ti-dac7612"},
> > + {}
> > +};
> > +MODULE_DEVICE_TABLE(spi, dac7612_id);
> > +
> > +static struct spi_driver dac7612_driver = {
> > + .driver = {
> > + .name = "ti-dac7612",
> > + },
> > + .probe = dac7612_probe,
> > + .id_table = dac7612_id,
> > +};
> > +module_spi_driver(dac7612_driver);
> > +
> > +MODULE_AUTHOR("Ricardo Ribalda <ricardo@xxxxxxxxxxx>");
> > +MODULE_DESCRIPTION("Texas Instruments DAC7612 DAC driver");
> > +MODULE_LICENSE("GPL v2");
>
--
Ricardo Ribalda