iio: dac: add support for stm32 DAC

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.

Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/dac/Kconfig

@@ -284,6 +284,21 @@ 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

drivers/iio/dac/Makefile

@@ -30,4 +30,6 @@ 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

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");

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 selected
+ */
+struct stm32_dac_common {
+	struct regmap			*regmap;
+	int				vref_mv;
+	bool				hfsel;
+};
+
+#endif