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SubjectRe: [PATCH 2/4] iio: dac: add support for stm32 DAC
On Fri, 31 Mar 2017, Fabrice Gasnier wrote:

> Add support for STMicroelectronics STM32 DAC. It's a 12-bit, voltage
> output digital-to-analog converter. It has two output channels, each
> with its own converter.
> It supports 8 bits or 12bits left/right aligned data format. Only
> 12bits right-aligned is used here. It has built-in noise or
> triangle waveform generator, and supports external triggers for
> conversions.
> Each channel can be used independently, with separate trigger, then
> separate IIO devices are used to handle this. Core driver is intended
> to share common resources such as clock, reset, reference voltage and
> registers.

comments below

> Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
> ---
> drivers/iio/dac/Kconfig | 15 ++
> drivers/iio/dac/Makefile | 2 +
> drivers/iio/dac/stm32-dac-core.c | 180 ++++++++++++++++++++++++
> drivers/iio/dac/stm32-dac-core.h | 51 +++++++
> drivers/iio/dac/stm32-dac.c | 296 +++++++++++++++++++++++++++++++++++++++
> 5 files changed, 544 insertions(+)
> create mode 100644 drivers/iio/dac/stm32-dac-core.c
> create mode 100644 drivers/iio/dac/stm32-dac-core.h
> create mode 100644 drivers/iio/dac/stm32-dac.c
>
> diff --git a/drivers/iio/dac/Kconfig b/drivers/iio/dac/Kconfig
> index d3084028..7198648 100644
> --- a/drivers/iio/dac/Kconfig
> +++ b/drivers/iio/dac/Kconfig
> @@ -274,6 +274,21 @@ config MCP4922
> To compile this driver as a module, choose M here: the module
> will be called mcp4922.
>
> +config STM32_DAC
> + tristate "STMicroelectronics STM32 DAC"
> + depends on (ARCH_STM32 && OF) || COMPILE_TEST
> + depends on REGULATOR
> + select STM32_DAC_CORE
> + help
> + Say yes here to build support for STMicroelectronics STM32 Digital
> + to Analog Converter (DAC).
> +
> + This driver can also be built as a module. If so, the module
> + will be called stm32-dac.
> +
> +config STM32_DAC_CORE
> + tristate
> +
> config VF610_DAC
> tristate "Vybrid vf610 DAC driver"
> depends on OF
> diff --git a/drivers/iio/dac/Makefile b/drivers/iio/dac/Makefile
> index f01bf4a..afe8ae7 100644
> --- a/drivers/iio/dac/Makefile
> +++ b/drivers/iio/dac/Makefile
> @@ -29,4 +29,6 @@ obj-$(CONFIG_MAX517) += max517.o
> obj-$(CONFIG_MAX5821) += max5821.o
> obj-$(CONFIG_MCP4725) += mcp4725.o
> obj-$(CONFIG_MCP4922) += mcp4922.o
> +obj-$(CONFIG_STM32_DAC_CORE) += stm32-dac-core.o
> +obj-$(CONFIG_STM32_DAC) += stm32-dac.o
> obj-$(CONFIG_VF610_DAC) += vf610_dac.o
> diff --git a/drivers/iio/dac/stm32-dac-core.c b/drivers/iio/dac/stm32-dac-core.c
> new file mode 100644
> index 0000000..75e4878
> --- /dev/null
> +++ b/drivers/iio/dac/stm32-dac-core.c
> @@ -0,0 +1,180 @@
> +/*
> + * This file is part of STM32 DAC driver
> + *
> + * Copyright (C) 2017, STMicroelectronics - All Rights Reserved
> + * Author: Fabrice Gasnier <fabrice.gasnier@st.com>.
> + *
> + * License type: GPLv2
> + *
> + * 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.
> + *
> + * This program is distributed in the hope that it will be useful, but
> + * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
> + * or FITNESS FOR A PARTICULAR PURPOSE.
> + * See the GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License along with
> + * this program. If not, see <http://www.gnu.org/licenses/>.
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/delay.h>
> +#include <linux/module.h>
> +#include <linux/of_platform.h>
> +#include <linux/regulator/consumer.h>
> +#include <linux/reset.h>
> +
> +#include "stm32-dac-core.h"
> +
> +/**
> + * struct stm32_dac_priv - stm32 DAC core private data
> + * @pclk: peripheral clock common for all DACs
> + * @rst: peripheral reset control
> + * @vref: regulator reference
> + * @common: Common data for all DAC instances
> + */
> +struct stm32_dac_priv {
> + struct clk *pclk;
> + struct reset_control *rst;
> + struct regulator *vref;
> + struct stm32_dac_common common;
> +};
> +
> +static struct stm32_dac_priv *to_stm32_dac_priv(struct stm32_dac_common *com)
> +{
> + return container_of(com, struct stm32_dac_priv, common);
> +}
> +
> +static const struct regmap_config stm32_dac_regmap_cfg = {
> + .reg_bits = 32,
> + .val_bits = 32,
> + .reg_stride = sizeof(u32),
> + .max_register = 0x3fc,
> +};
> +
> +static int stm32_dac_probe(struct platform_device *pdev)
> +{
> + struct device *dev = &pdev->dev;
> + struct stm32_dac_priv *priv;
> + struct regmap *regmap;
> + struct resource *res;
> + void __iomem *mmio;
> + int ret;
> +
> + if (!dev->of_node)
> + return -ENODEV;
> +
> + priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
> + if (!priv)
> + return -ENOMEM;
> +
> + res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> + mmio = devm_ioremap_resource(dev, res);
> + if (IS_ERR(mmio))
> + return PTR_ERR(mmio);
> +
> + regmap = devm_regmap_init_mmio(dev, mmio, &stm32_dac_regmap_cfg);
> + if (IS_ERR(regmap))
> + return PTR_ERR(regmap);
> + priv->common.regmap = regmap;
> +
> + priv->vref = devm_regulator_get(dev, "vref");
> + if (IS_ERR(priv->vref)) {
> + ret = PTR_ERR(priv->vref);
> + dev_err(dev, "vref get failed, %d\n", ret);
> + return ret;
> + }
> +
> + ret = regulator_enable(priv->vref);
> + if (ret < 0) {
> + dev_err(dev, "vref enable failed\n");
> + return ret;
> + }
> +
> + ret = regulator_get_voltage(priv->vref);
> + if (ret < 0) {
> + dev_err(dev, "vref get voltage failed, %d\n", ret);
> + goto err_vref;
> + }
> + priv->common.vref_mv = ret / 1000;
> + dev_dbg(dev, "vref+=%dmV\n", priv->common.vref_mv);
> +
> + priv->pclk = devm_clk_get(dev, "pclk");
> + if (IS_ERR(priv->pclk)) {
> + ret = PTR_ERR(priv->pclk);
> + dev_err(dev, "pclk get failed\n");
> + goto err_vref;
> + }
> +
> + ret = clk_prepare_enable(priv->pclk);
> + if (ret < 0) {
> + dev_err(dev, "pclk enable failed\n");
> + goto err_vref;
> + }
> +
> + priv->rst = devm_reset_control_get(dev, NULL);
> + if (!IS_ERR(priv->rst)) {
> + reset_control_assert(priv->rst);
> + udelay(2);
> + reset_control_deassert(priv->rst);
> + }
> +
> + /* When clock speed is higher than 80MHz, set HFSEL */
> + priv->common.hfsel = (clk_get_rate(priv->pclk) > 80000000UL);
> + ret = regmap_update_bits(regmap, STM32_DAC_CR, STM32H7_DAC_CR_HFSEL,
> + priv->common.hfsel ? STM32H7_DAC_CR_HFSEL : 0);
> + if (ret)
> + goto err_pclk;
> +
> + platform_set_drvdata(pdev, &priv->common);
> +
> + ret = of_platform_populate(pdev->dev.of_node, NULL, NULL, dev);
> + if (ret < 0) {
> + dev_err(dev, "failed to populate DT children\n");
> + goto err_pclk;
> + }
> +
> + return 0;
> +
> +err_pclk:
> + clk_disable_unprepare(priv->pclk);
> +err_vref:
> + regulator_disable(priv->vref);
> +
> + return ret;
> +}
> +
> +static int stm32_dac_remove(struct platform_device *pdev)
> +{
> + struct stm32_dac_common *common = platform_get_drvdata(pdev);
> + struct stm32_dac_priv *priv = to_stm32_dac_priv(common);
> +
> + of_platform_depopulate(&pdev->dev);
> + clk_disable_unprepare(priv->pclk);
> + regulator_disable(priv->vref);
> +
> + return 0;
> +}
> +
> +static const struct of_device_id stm32_dac_of_match[] = {
> + { .compatible = "st,stm32h7-dac-core", },
> + {},
> +};
> +MODULE_DEVICE_TABLE(of, stm32_dac_of_match);
> +
> +static struct platform_driver stm32_dac_driver = {
> + .probe = stm32_dac_probe,
> + .remove = stm32_dac_remove,
> + .driver = {
> + .name = "stm32-dac-core",
> + .of_match_table = stm32_dac_of_match,
> + },
> +};
> +module_platform_driver(stm32_dac_driver);
> +
> +MODULE_AUTHOR("Fabrice Gasnier <fabrice.gasnier@st.com>");
> +MODULE_DESCRIPTION("STMicroelectronics STM32 DAC core driver");
> +MODULE_LICENSE("GPL v2");
> +MODULE_ALIAS("platform:stm32-dac-core");
> diff --git a/drivers/iio/dac/stm32-dac-core.h b/drivers/iio/dac/stm32-dac-core.h
> new file mode 100644
> index 0000000..d3099f7
> --- /dev/null
> +++ b/drivers/iio/dac/stm32-dac-core.h
> @@ -0,0 +1,51 @@
> +/*
> + * This file is part of STM32 DAC driver
> + *
> + * Copyright (C) 2017, STMicroelectronics - All Rights Reserved
> + * Author: Fabrice Gasnier <fabrice.gasnier@st.com>.
> + *
> + * License type: GPLv2
> + *
> + * 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.
> + *
> + * This program is distributed in the hope that it will be useful, but
> + * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
> + * or FITNESS FOR A PARTICULAR PURPOSE.
> + * See the GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License along with
> + * this program. If not, see <http://www.gnu.org/licenses/>.
> + */
> +
> +#ifndef __STM32_DAC_CORE_H
> +#define __STM32_DAC_CORE_H
> +
> +#include <linux/regmap.h>
> +
> +/* STM32 DAC registers */
> +#define STM32_DAC_CR 0x00
> +#define STM32_DAC_DHR12R1 0x08
> +#define STM32_DAC_DHR12R2 0x14
> +#define STM32_DAC_DOR1 0x2C
> +#define STM32_DAC_DOR2 0x30
> +
> +/* STM32_DAC_CR bit fields */
> +#define STM32_DAC_CR_EN1 BIT(0)
> +#define STM32H7_DAC_CR_HFSEL BIT(15)
> +#define STM32_DAC_CR_EN2 BIT(16)
> +
> +/**
> + * struct stm32_dac_common - stm32 DAC driver common data (for all instances)
> + * @regmap: DAC registers shared via regmap
> + * @vref_mv: reference voltage (mv)
> + * @hfsel: high speed bus clock

probably better "high speed bus clock selected"

> + */
> +struct stm32_dac_common {
> + struct regmap *regmap;
> + int vref_mv;
> + bool hfsel;
> +};
> +
> +#endif
> diff --git a/drivers/iio/dac/stm32-dac.c b/drivers/iio/dac/stm32-dac.c
> new file mode 100644
> index 0000000..ee9711d
> --- /dev/null
> +++ b/drivers/iio/dac/stm32-dac.c
> @@ -0,0 +1,296 @@
> +/*
> + * This file is part of STM32 DAC driver
> + *
> + * Copyright (C) 2017, STMicroelectronics - All Rights Reserved
> + * Authors: Amelie Delaunay <amelie.delaunay@st.com>
> + * Fabrice Gasnier <fabrice.gasnier@st.com>
> + *
> + * License type: GPLv2
> + *
> + * 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.
> + *
> + * This program is distributed in the hope that it will be useful, but
> + * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
> + * or FITNESS FOR A PARTICULAR PURPOSE.
> + * See the GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License along with
> + * this program. If not, see <http://www.gnu.org/licenses/>.
> + */
> +
> +#include <linux/bitfield.h>
> +#include <linux/delay.h>
> +#include <linux/iio/iio.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +
> +#include "stm32-dac-core.h"
> +
> +#define STM32_DAC_CHANNEL_1 1
> +#define STM32_DAC_CHANNEL_2 2
> +
> +/**
> + * struct stm32_dac - private data of DAC driver
> + * @common: reference to DAC common data
> + */
> +struct stm32_dac {
> + struct stm32_dac_common *common;
> +};
> +
> +static int stm32_dac_is_enabled(struct stm32_dac *dac, int channel)
> +{
> + u32 en, val;
> + int ret;
> +
> + ret = regmap_read(dac->common->regmap, STM32_DAC_CR, &val);
> + if (ret < 0)
> + return ret;
> + if (channel == STM32_DAC_CHANNEL_1)
> + en = FIELD_GET(STM32_DAC_CR_EN1, val);
> + else
> + en = FIELD_GET(STM32_DAC_CR_EN2, val);
> +
> + return !!en;
> +}
> +
> +static int stm32_dac_enable(struct iio_dev *indio_dev, int channel)
> +{
> + struct stm32_dac *dac = iio_priv(indio_dev);
> + u32 en = (channel == STM32_DAC_CHANNEL_1) ?
> + STM32_DAC_CR_EN1 : STM32_DAC_CR_EN2;

could #define a macro to select CR_EN1 or CR_EN2 depending on channel; to
use here and above and below

or maybe a table to select all the channel-specific constants indexed by
channel

> + int ret;
> +
> + ret = regmap_update_bits(dac->common->regmap, STM32_DAC_CR, en, en);
> + if (ret < 0) {
> + dev_err(&indio_dev->dev, "Enable failed\n");
> + return ret;
> + }
> +
> + /*
> + * When HFSEL is set, it is not allowed to write the DHRx register
> + * during 8 clock cycles after the ENx bit is set. It is not allowed
> + * to make software/hardware trigger during this period neither.

neither -> either

> + */
> + if (dac->common->hfsel)
> + udelay(1);
> +
> + return 0;
> +}
> +
> +static int stm32_dac_disable(struct iio_dev *indio_dev, int channel)
> +{
> + struct stm32_dac *dac = iio_priv(indio_dev);
> + u32 en = (channel == STM32_DAC_CHANNEL_1) ?
> + STM32_DAC_CR_EN1 : STM32_DAC_CR_EN2;
> + int ret;
> +
> + ret = regmap_update_bits(dac->common->regmap, STM32_DAC_CR, en, 0);
> + if (ret)
> + dev_err(&indio_dev->dev, "Disable failed\n");
> +
> + return ret;
> +}
> +
> +static int stm32_dac_get_value(struct stm32_dac *dac, int channel, int *val)
> +{
> + int ret;
> +
> + if (channel == STM32_DAC_CHANNEL_1)
> + ret = regmap_read(dac->common->regmap, STM32_DAC_DOR1, val);
> + else
> + ret = regmap_read(dac->common->regmap, STM32_DAC_DOR2, val);
> +
> + return ret ? ret : IIO_VAL_INT;
> +}
> +
> +static int stm32_dac_set_value(struct stm32_dac *dac, int channel, int val)
> +{
> + int ret;
> +
> + if (channel == STM32_DAC_CHANNEL_1)
> + ret = regmap_write(dac->common->regmap, STM32_DAC_DHR12R1, val);
> + else
> + ret = regmap_write(dac->common->regmap, STM32_DAC_DHR12R2, val);
> +
> + return ret;
> +}
> +
> +static int stm32_dac_read_raw(struct iio_dev *indio_dev,
> + struct iio_chan_spec const *chan,
> + int *val, int *val2, long mask)
> +{
> + struct stm32_dac *dac = iio_priv(indio_dev);
> + int ret;
> +
> + switch (mask) {
> + case IIO_CHAN_INFO_RAW:
> + return stm32_dac_get_value(dac, chan->channel, val);
> + case IIO_CHAN_INFO_SCALE:
> + *val = dac->common->vref_mv;
> + *val2 = chan->scan_type.realbits;
> + return IIO_VAL_FRACTIONAL_LOG2;
> + case IIO_CHAN_INFO_ENABLE:
> + ret = stm32_dac_is_enabled(dac, chan->channel);
> + if (ret < 0)
> + return ret;
> + *val = ret;
> + return IIO_VAL_INT;
> + default:
> + return -EINVAL;
> + }
> +}
> +
> +static int stm32_dac_write_raw(struct iio_dev *indio_dev,
> + struct iio_chan_spec const *chan,
> + int val, int val2, long mask)
> +{
> + struct stm32_dac *dac = iio_priv(indio_dev);
> +
> + switch (mask) {
> + case IIO_CHAN_INFO_RAW:
> + return stm32_dac_set_value(dac, chan->channel, val);
> + case IIO_CHAN_INFO_ENABLE:
> + if (!!val)
> + return stm32_dac_enable(indio_dev, chan->channel);
> + else
> + return stm32_dac_disable(indio_dev, chan->channel);
> + default:
> + return -EINVAL;
> + }
> +}
> +
> +static int stm32_dac_debugfs_reg_access(struct iio_dev *indio_dev,
> + unsigned reg, unsigned writeval,
> + unsigned *readval)
> +{
> + struct stm32_dac *dac = iio_priv(indio_dev);
> +
> + if (!readval)
> + return regmap_write(dac->common->regmap, reg, writeval);
> + else
> + return regmap_read(dac->common->regmap, reg, readval);
> +}
> +
> +static const struct iio_info stm32_dac_iio_info = {
> + .read_raw = &stm32_dac_read_raw,

no & for functions (matter of taste)

> + .write_raw = &stm32_dac_write_raw,
> + .debugfs_reg_access = &stm32_dac_debugfs_reg_access,
> + .driver_module = THIS_MODULE,
> +};
> +
> +#define STM32_DAC_CHANNEL(chan, name) { \
> + .type = IIO_VOLTAGE, \
> + .indexed = 1, \
> + .output = 1, \
> + .channel = chan, \
> + .info_mask_separate = \
> + BIT(IIO_CHAN_INFO_RAW) | \
> + BIT(IIO_CHAN_INFO_ENABLE) | \
> + BIT(IIO_CHAN_INFO_SCALE), \
> + .scan_type = { \

scan_type is no needed (yet) and scan_index is missing (or always 0 which
becomes clear below, a comment may be helpful)

> + .sign = 'u', \
> + .realbits = 12, \
> + .storagebits = 16, \
> + }, \
> + .datasheet_name = name, \
> +}
> +
> +static const struct iio_chan_spec stm32_dac_channels[] = {
> + STM32_DAC_CHANNEL(STM32_DAC_CHANNEL_1, "out1"),
> + STM32_DAC_CHANNEL(STM32_DAC_CHANNEL_2, "out2"),
> +};
> +
> +static int stm32_dac_chan_of_init(struct iio_dev *indio_dev)
> +{
> + struct device_node *np = indio_dev->dev.of_node;
> + unsigned int i;
> + u32 channel;
> + int ret;
> +
> + ret = of_property_read_u32(np, "st,dac-channel", &channel);
> + if (ret) {
> + dev_err(&indio_dev->dev, "Failed to read st,dac-channel\n");
> + return ret;
> + }
> +
> + for (i = 0; i < ARRAY_SIZE(stm32_dac_channels); i++) {
> + if (stm32_dac_channels[i].channel == channel)
> + break;
> + }
> + if (i >= ARRAY_SIZE(stm32_dac_channels)) {
> + dev_err(&indio_dev->dev, "Invalid st,dac-channel\n");
> + return -EINVAL;
> + }
> +
> + indio_dev->channels = &stm32_dac_channels[i];
> + indio_dev->num_channels = 1;

this is unusual, a comment would be helpful
why not expose both channels?

> +
> + return 0;
> +};
> +
> +static int stm32_dac_probe(struct platform_device *pdev)
> +{
> + struct device_node *np = pdev->dev.of_node;
> + struct iio_dev *indio_dev;
> + struct stm32_dac *dac;
> + int ret;
> +
> + if (!np)
> + return -ENODEV;
> +
> + indio_dev = devm_iio_device_alloc(&pdev->dev, sizeof(*dac));
> + if (!indio_dev)
> + return -ENOMEM;
> + platform_set_drvdata(pdev, indio_dev);
> +
> + dac = iio_priv(indio_dev);
> + dac->common = dev_get_drvdata(pdev->dev.parent);
> + indio_dev->name = dev_name(&pdev->dev);
> + indio_dev->dev.parent = &pdev->dev;
> + indio_dev->dev.of_node = pdev->dev.of_node;
> + indio_dev->info = &stm32_dac_iio_info;
> + indio_dev->modes = INDIO_DIRECT_MODE;
> +
> + ret = stm32_dac_chan_of_init(indio_dev);
> + if (ret < 0)
> + return ret;
> +
> + ret = iio_device_register(indio_dev);

just
return iio_device_register();

candidate for devm_ due to empty _remove()

> + if (ret)
> + return ret;
> +
> + return 0;
> +}
> +
> +static int stm32_dac_remove(struct platform_device *pdev)
> +{
> + struct iio_dev *indio_dev = platform_get_drvdata(pdev);
> +
> + iio_device_unregister(indio_dev);
> +
> + return 0;
> +}
> +
> +static const struct of_device_id stm32_dac_of_match[] = {
> + { .compatible = "st,stm32-dac", },
> + {},
> +};
> +MODULE_DEVICE_TABLE(of, stm32_dac_of_match);
> +
> +static struct platform_driver stm32_dac_driver = {
> + .probe = stm32_dac_probe,
> + .remove = stm32_dac_remove,
> + .driver = {
> + .name = "stm32-dac",
> + .of_match_table = stm32_dac_of_match,
> + },
> +};
> +module_platform_driver(stm32_dac_driver);
> +
> +MODULE_ALIAS("platform:stm32-dac");
> +MODULE_AUTHOR("Amelie Delaunay <amelie.delaunay@st.com>");
> +MODULE_DESCRIPTION("STMicroelectronics STM32 DAC driver");
> +MODULE_LICENSE("GPL v2");
>

--

Peter Meerwald-Stadler
Mobile: +43 664 24 44 418

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