iio: adc: Add support for STM32 ADC core

Add core driver for STMicroelectronics STM32 ADC (Analog to Digital
Converter). STM32 ADC can be composed of up to 3 ADCs with shared
resources like clock prescaler, common interrupt line and analog
reference voltage.
This core driver basically manages shared resources.

Signed-off-by: Fabrice Gasnier <[e-mail]>
Signed-off-by: Jonathan Cameron <[e-mail]>

drivers/iio/adc/Kconfig

···
 	  To compile this driver as a module, choose M here: the
 	  module will be called rockchip_saradc.
 
+config STM32_ADC_CORE
+	tristate "STMicroelectronics STM32 adc core"
+	depends on ARCH_STM32 || COMPILE_TEST
+	depends on OF
+	depends on REGULATOR
+	help
+	  Select this option to enable the core driver for STMicroelectronics
+	  STM32 analog-to-digital converter (ADC).
+
+	  This driver can also be built as a module.  If so, the module
+	  will be called stm32-adc-core.
+
 config STX104
 	tristate "Apex Embedded Systems STX104 driver"
 	depends on X86 && ISA_BUS_API

drivers/iio/adc/Makefile

···
 obj-$(CONFIG_QCOM_SPMI_VADC) += qcom-spmi-vadc.o
 obj-$(CONFIG_ROCKCHIP_SARADC) += rockchip_saradc.o
 obj-$(CONFIG_STX104) += stx104.o
+obj-$(CONFIG_STM32_ADC_CORE) += stm32-adc-core.o
 obj-$(CONFIG_TI_ADC081C) += ti-adc081c.o
 obj-$(CONFIG_TI_ADC0832) += ti-adc0832.o
 obj-$(CONFIG_TI_ADC12138) += ti-adc12138.o

drivers/iio/adc/stm32-adc-core.c

···
+/*
+ * This file is part of STM32 ADC driver
+ *
+ * Copyright (C) 2016, STMicroelectronics - All Rights Reserved
+ * Author: Fabrice Gasnier <[e-mail]>.
+ *
+ * Inspired from: fsl-imx25-tsadc
+ *
+ * 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/interrupt.h>
+#include <linux/irqchip/chained_irq.h>
+#include <linux/irqdesc.h>
+#include <linux/irqdomain.h>
+#include <linux/module.h>
+#include <linux/of_device.h>
+#include <linux/regulator/consumer.h>
+#include <linux/slab.h>
+
+#include "stm32-adc-core.h"
+
+/* STM32F4 - common registers for all ADC instances: 1, 2 & 3 */
+#define STM32F4_ADC_CSR			(STM32_ADCX_COMN_OFFSET + 0x00)
+#define STM32F4_ADC_CCR			(STM32_ADCX_COMN_OFFSET + 0x04)
+
+/* STM32F4_ADC_CSR - bit fields */
+#define STM32F4_EOC3			BIT(17)
+#define STM32F4_EOC2			BIT(9)
+#define STM32F4_EOC1			BIT(1)
+
+/* STM32F4_ADC_CCR - bit fields */
+#define STM32F4_ADC_ADCPRE_SHIFT	16
+#define STM32F4_ADC_ADCPRE_MASK		GENMASK(17, 16)
+
+/* STM32 F4 maximum analog clock rate (from datasheet) */
+#define STM32F4_ADC_MAX_CLK_RATE	36000000
+
+/**
+ * struct stm32_adc_priv - stm32 ADC core private data
+ * @irq:		irq for ADC block
+ * @domain:		irq domain reference
+ * @aclk:		clock reference for the analog circuitry
+ * @vref:		regulator reference
+ * @common:		common data for all ADC instances
+ */
+struct stm32_adc_priv {
+	int				irq;
+	struct irq_domain		*domain;
+	struct clk			*aclk;
+	struct regulator		*vref;
+	struct stm32_adc_common		common;
+};
+
+static struct stm32_adc_priv *to_stm32_adc_priv(struct stm32_adc_common *com)
+{
+	return container_of(com, struct stm32_adc_priv, common);
+}
+
+/* STM32F4 ADC internal common clock prescaler division ratios */
+static int stm32f4_pclk_div[] = {2, 4, 6, 8};
+
+/**
+ * stm32f4_adc_clk_sel() - Select stm32f4 ADC common clock prescaler
+ * @priv: stm32 ADC core private data
+ * Select clock prescaler used for analog conversions, before using ADC.
+ */
+static int stm32f4_adc_clk_sel(struct platform_device *pdev,
+			       struct stm32_adc_priv *priv)
+{
+	unsigned long rate;
+	u32 val;
+	int i;
+
+	rate = clk_get_rate(priv->aclk);
+	for (i = 0; i < ARRAY_SIZE(stm32f4_pclk_div); i++) {
+		if ((rate / stm32f4_pclk_div[i]) <= STM32F4_ADC_MAX_CLK_RATE)
+			break;
+	}
+	if (i >= ARRAY_SIZE(stm32f4_pclk_div))
+		return -EINVAL;
+
+	val = readl_relaxed(priv->common.base + STM32F4_ADC_CCR);
+	val &= ~STM32F4_ADC_ADCPRE_MASK;
+	val |= i << STM32F4_ADC_ADCPRE_SHIFT;
+	writel_relaxed(val, priv->common.base + STM32F4_ADC_CCR);
+
+	dev_dbg(&pdev->dev, "Using analog clock source at %ld kHz\n",
+		rate / (stm32f4_pclk_div[i] * 1000));
+
+	return 0;
+}
+
+/* ADC common interrupt for all instances */
+static void stm32_adc_irq_handler(struct irq_desc *desc)
+{
+	struct stm32_adc_priv *priv = irq_desc_get_handler_data(desc);
+	struct irq_chip *chip = irq_desc_get_chip(desc);
+	u32 status;
+
+	chained_irq_enter(chip, desc);
+	status = readl_relaxed(priv->common.base + STM32F4_ADC_CSR);
+
+	if (status & STM32F4_EOC1)
+		generic_handle_irq(irq_find_mapping(priv->domain, 0));
+
+	if (status & STM32F4_EOC2)
+		generic_handle_irq(irq_find_mapping(priv->domain, 1));
+
+	if (status & STM32F4_EOC3)
+		generic_handle_irq(irq_find_mapping(priv->domain, 2));
+
+	chained_irq_exit(chip, desc);
+};
+
+static int stm32_adc_domain_map(struct irq_domain *d, unsigned int irq,
+				irq_hw_number_t hwirq)
+{
+	irq_set_chip_data(irq, d->host_data);
+	irq_set_chip_and_handler(irq, &dummy_irq_chip, handle_level_irq);
+
+	return 0;
+}
+
+static void stm32_adc_domain_unmap(struct irq_domain *d, unsigned int irq)
+{
+	irq_set_chip_and_handler(irq, NULL, NULL);
+	irq_set_chip_data(irq, NULL);
+}
+
+static const struct irq_domain_ops stm32_adc_domain_ops = {
+	.map = stm32_adc_domain_map,
+	.unmap  = stm32_adc_domain_unmap,
+	.xlate = irq_domain_xlate_onecell,
+};
+
+static int stm32_adc_irq_probe(struct platform_device *pdev,
+			       struct stm32_adc_priv *priv)
+{
+	struct device_node *np = pdev->dev.of_node;
+
+	priv->irq = platform_get_irq(pdev, 0);
+	if (priv->irq < 0) {
+		dev_err(&pdev->dev, "failed to get irq\n");
+		return priv->irq;
+	}
+
+	priv->domain = irq_domain_add_simple(np, STM32_ADC_MAX_ADCS, 0,
+					     &stm32_adc_domain_ops,
+					     priv);
+	if (!priv->domain) {
+		dev_err(&pdev->dev, "Failed to add irq domain\n");
+		return -ENOMEM;
+	}
+
+	irq_set_chained_handler(priv->irq, stm32_adc_irq_handler);
+	irq_set_handler_data(priv->irq, priv);
+
+	return 0;
+}
+
+static void stm32_adc_irq_remove(struct platform_device *pdev,
+				 struct stm32_adc_priv *priv)
+{
+	int hwirq;
+
+	for (hwirq = 0; hwirq < STM32_ADC_MAX_ADCS; hwirq++)
+		irq_dispose_mapping(irq_find_mapping(priv->domain, hwirq));
+	irq_domain_remove(priv->domain);
+	irq_set_chained_handler(priv->irq, NULL);
+}
+
+static int stm32_adc_probe(struct platform_device *pdev)
+{
+	struct stm32_adc_priv *priv;
+	struct device_node *np = pdev->dev.of_node;
+	struct resource *res;
+	int ret;
+
+	if (!pdev->dev.of_node)
+		return -ENODEV;
+
+	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	priv->common.base = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(priv->common.base))
+		return PTR_ERR(priv->common.base);
+
+	priv->vref = devm_regulator_get(&pdev->dev, "vref");
+	if (IS_ERR(priv->vref)) {
+		ret = PTR_ERR(priv->vref);
+		dev_err(&pdev->dev, "vref get failed, %d\n", ret);
+		return ret;
+	}
+
+	ret = regulator_enable(priv->vref);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "vref enable failed\n");
+		return ret;
+	}
+
+	ret = regulator_get_voltage(priv->vref);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "vref get voltage failed, %d\n", ret);
+		goto err_regulator_disable;
+	}
+	priv->common.vref_mv = ret / 1000;
+	dev_dbg(&pdev->dev, "vref+=%dmV\n", priv->common.vref_mv);
+
+	priv->aclk = devm_clk_get(&pdev->dev, "adc");
+	if (IS_ERR(priv->aclk)) {
+		ret = PTR_ERR(priv->aclk);
+		dev_err(&pdev->dev, "Can't get 'adc' clock\n");
+		goto err_regulator_disable;
+	}
+
+	ret = clk_prepare_enable(priv->aclk);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "adc clk enable failed\n");
+		goto err_regulator_disable;
+	}
+
+	ret = stm32f4_adc_clk_sel(pdev, priv);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "adc clk selection failed\n");
+		goto err_clk_disable;
+	}
+
+	ret = stm32_adc_irq_probe(pdev, priv);
+	if (ret < 0)
+		goto err_clk_disable;
+
+	platform_set_drvdata(pdev, &priv->common);
+
+	ret = of_platform_populate(np, NULL, NULL, &pdev->dev);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "failed to populate DT children\n");
+		goto err_irq_remove;
+	}
+
+	return 0;
+
+err_irq_remove:
+	stm32_adc_irq_remove(pdev, priv);
+
+err_clk_disable:
+	clk_disable_unprepare(priv->aclk);
+
+err_regulator_disable:
+	regulator_disable(priv->vref);
+
+	return ret;
+}
+
+static int stm32_adc_remove(struct platform_device *pdev)
+{
+	struct stm32_adc_common *common = platform_get_drvdata(pdev);
+	struct stm32_adc_priv *priv = to_stm32_adc_priv(common);
+
+	of_platform_depopulate(&pdev->dev);
+	stm32_adc_irq_remove(pdev, priv);
+	clk_disable_unprepare(priv->aclk);
+	regulator_disable(priv->vref);
+
+	return 0;
+}
+
+static const struct of_device_id stm32_adc_of_match[] = {
+	{ .compatible = "st,stm32f4-adc-core" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, stm32_adc_of_match);
+
+static struct platform_driver stm32_adc_driver = {
+	.probe = stm32_adc_probe,
+	.remove = stm32_adc_remove,
+	.driver = {
+		.name = "stm32-adc-core",
+		.of_match_table = stm32_adc_of_match,
+	},
+};
+module_platform_driver(stm32_adc_driver);
+
+MODULE_AUTHOR("Fabrice Gasnier <[e-mail]>");
+MODULE_DESCRIPTION("STMicroelectronics STM32 ADC core driver");
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS("platform:stm32-adc-core");

drivers/iio/adc/stm32-adc-core.h

···
+/*
+ * This file is part of STM32 ADC driver
+ *
+ * Copyright (C) 2016, STMicroelectronics - All Rights Reserved
+ * Author: Fabrice Gasnier <[e-mail]>.
+ *
+ * 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_ADC_H
+#define __STM32_ADC_H
+
+/*
+ * STM32 - ADC global register map
+ * ________________________________________________________
+ * | Offset |                 Register                    |
+ * --------------------------------------------------------
+ * | 0x000  |                Master ADC1                  |
+ * --------------------------------------------------------
+ * | 0x100  |                Slave ADC2                   |
+ * --------------------------------------------------------
+ * | 0x200  |                Slave ADC3                   |
+ * --------------------------------------------------------
+ * | 0x300  |         Master & Slave common regs          |
+ * --------------------------------------------------------
+ */
+#define STM32_ADC_MAX_ADCS		3
+#define STM32_ADCX_COMN_OFFSET		0x300
+
+/**
+ * struct stm32_adc_common - stm32 ADC driver common data (for all instances)
+ * @base:		control registers base cpu addr
+ * @vref_mv:		vref voltage (mv)
+ */
+struct stm32_adc_common {
+	void __iomem			*base;
+	int				vref_mv;
+};
+
+#endif