IIO: ADC: add stm32 DFSDM core support

Add driver for stm32 DFSDM pheripheral. Its converts a sigma delta
stream in n bit samples through a low pass filter and an integrator.
stm32-dfsdm-core driver is the core part supporting the filter
instances dedicated to sigma-delta ADC or audio PDM microphone purpose.
Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@st.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/iio/adc/Kconfig

@@ -668,6 +668,18 @@ config STM32_ADC
 	  This driver can also be built as a module.  If so, the module
 	  will be called stm32-adc.
 
+config STM32_DFSDM_CORE
+	tristate "STMicroelectronics STM32 DFSDM core"
+	depends on (ARCH_STM32 && OF) || COMPILE_TEST
+	select REGMAP
+	select REGMAP_MMIO
+	help
+	  Select this option to enable the  driver for STMicroelectronics
+	  STM32 digital filter for sigma delta converter.
+
+	  This driver can also be built as a module.  If so, the module
+	  will be called stm32-dfsdm-core.
+
 config STX104
 	tristate "Apex Embedded Systems STX104 driver"
 	depends on PC104 && X86 && ISA_BUS_API

drivers/iio/adc/Makefile

@@ -64,6 +64,7 @@ obj-$(CONFIG_STX104) += stx104.o
 obj-$(CONFIG_SUN4I_GPADC) += sun4i-gpadc-iio.o
 obj-$(CONFIG_STM32_ADC_CORE) += stm32-adc-core.o
 obj-$(CONFIG_STM32_ADC) += stm32-adc.o
+obj-$(CONFIG_STM32_DFSDM_CORE) += stm32-dfsdm-core.o
 obj-$(CONFIG_TI_ADC081C) += ti-adc081c.o
 obj-$(CONFIG_TI_ADC0832) += ti-adc0832.o
 obj-$(CONFIG_TI_ADC084S021) += ti-adc084s021.o

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

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * This file is part the core part STM32 DFSDM driver
+ *
+ * Copyright (C) 2017, STMicroelectronics - All Rights Reserved
+ * Author(s): Arnaud Pouliquen <arnaud.pouliquen@st.com> for STMicroelectronics.
+ */
+
+#include <linux/clk.h>
+#include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
+#include <linux/interrupt.h>
+#include <linux/module.h>
+#include <linux/of_device.h>
+#include <linux/regmap.h>
+#include <linux/slab.h>
+
+#include "stm32-dfsdm.h"
+
+struct stm32_dfsdm_dev_data {
+	unsigned int num_filters;
+	unsigned int num_channels;
+	const struct regmap_config *regmap_cfg;
+};
+
+#define STM32H7_DFSDM_NUM_FILTERS	4
+#define STM32H7_DFSDM_NUM_CHANNELS	8
+
+static bool stm32_dfsdm_volatile_reg(struct device *dev, unsigned int reg)
+{
+	if (reg < DFSDM_FILTER_BASE_ADR)
+		return false;
+
+	/*
+	 * Mask is done on register to avoid to list registers of all
+	 * filter instances.
+	 */
+	switch (reg & DFSDM_FILTER_REG_MASK) {
+	case DFSDM_CR1(0) & DFSDM_FILTER_REG_MASK:
+	case DFSDM_ISR(0) & DFSDM_FILTER_REG_MASK:
+	case DFSDM_JDATAR(0) & DFSDM_FILTER_REG_MASK:
+	case DFSDM_RDATAR(0) & DFSDM_FILTER_REG_MASK:
+		return true;
+	}
+
+	return false;
+}
+
+static const struct regmap_config stm32h7_dfsdm_regmap_cfg = {
+	.reg_bits = 32,
+	.val_bits = 32,
+	.reg_stride = sizeof(u32),
+	.max_register = 0x2B8,
+	.volatile_reg = stm32_dfsdm_volatile_reg,
+	.fast_io = true,
+};
+
+static const struct stm32_dfsdm_dev_data stm32h7_dfsdm_data = {
+	.num_filters = STM32H7_DFSDM_NUM_FILTERS,
+	.num_channels = STM32H7_DFSDM_NUM_CHANNELS,
+	.regmap_cfg = &stm32h7_dfsdm_regmap_cfg,
+};
+
+struct dfsdm_priv {
+	struct platform_device *pdev; /* platform device */
+
+	struct stm32_dfsdm dfsdm; /* common data exported for all instances */
+
+	unsigned int spi_clk_out_div; /* SPI clkout divider value */
+	atomic_t n_active_ch;	/* number of current active channels */
+
+	struct clk *clk; /* DFSDM clock */
+	struct clk *aclk; /* audio clock */
+};
+
+/**
+ * stm32_dfsdm_start_dfsdm - start global dfsdm interface.
+ *
+ * Enable interface if n_active_ch is not null.
+ * @dfsdm: Handle used to retrieve dfsdm context.
+ */
+int stm32_dfsdm_start_dfsdm(struct stm32_dfsdm *dfsdm)
+{
+	struct dfsdm_priv *priv = container_of(dfsdm, struct dfsdm_priv, dfsdm);
+	struct device *dev = &priv->pdev->dev;
+	unsigned int clk_div = priv->spi_clk_out_div;
+	int ret;
+
+	if (atomic_inc_return(&priv->n_active_ch) == 1) {
+		ret = clk_prepare_enable(priv->clk);
+		if (ret < 0) {
+			dev_err(dev, "Failed to start clock\n");
+			goto error_ret;
+		}
+		if (priv->aclk) {
+			ret = clk_prepare_enable(priv->aclk);
+			if (ret < 0) {
+				dev_err(dev, "Failed to start audio clock\n");
+				goto disable_clk;
+			}
+		}
+
+		/* Output the SPI CLKOUT (if clk_div == 0 clock if OFF) */
+		ret = regmap_update_bits(dfsdm->regmap, DFSDM_CHCFGR1(0),
+					 DFSDM_CHCFGR1_CKOUTDIV_MASK,
+					 DFSDM_CHCFGR1_CKOUTDIV(clk_div));
+		if (ret < 0)
+			goto disable_aclk;
+
+		/* Global enable of DFSDM interface */
+		ret = regmap_update_bits(dfsdm->regmap, DFSDM_CHCFGR1(0),
+					 DFSDM_CHCFGR1_DFSDMEN_MASK,
+					 DFSDM_CHCFGR1_DFSDMEN(1));
+		if (ret < 0)
+			goto disable_aclk;
+	}
+
+	dev_dbg(dev, "%s: n_active_ch %d\n", __func__,
+		atomic_read(&priv->n_active_ch));
+
+	return 0;
+
+disable_aclk:
+	clk_disable_unprepare(priv->aclk);
+disable_clk:
+	clk_disable_unprepare(priv->clk);
+
+error_ret:
+	atomic_dec(&priv->n_active_ch);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(stm32_dfsdm_start_dfsdm);
+
+/**
+ * stm32_dfsdm_stop_dfsdm - stop global DFSDM interface.
+ *
+ * Disable interface if n_active_ch is null
+ * @dfsdm: Handle used to retrieve dfsdm context.
+ */
+int stm32_dfsdm_stop_dfsdm(struct stm32_dfsdm *dfsdm)
+{
+	struct dfsdm_priv *priv = container_of(dfsdm, struct dfsdm_priv, dfsdm);
+	int ret;
+
+	if (atomic_dec_and_test(&priv->n_active_ch)) {
+		/* Global disable of DFSDM interface */
+		ret = regmap_update_bits(dfsdm->regmap, DFSDM_CHCFGR1(0),
+					 DFSDM_CHCFGR1_DFSDMEN_MASK,
+					 DFSDM_CHCFGR1_DFSDMEN(0));
+		if (ret < 0)
+			return ret;
+
+		/* Stop SPI CLKOUT */
+		ret = regmap_update_bits(dfsdm->regmap, DFSDM_CHCFGR1(0),
+					 DFSDM_CHCFGR1_CKOUTDIV_MASK,
+					 DFSDM_CHCFGR1_CKOUTDIV(0));
+		if (ret < 0)
+			return ret;
+
+		clk_disable_unprepare(priv->clk);
+		if (priv->aclk)
+			clk_disable_unprepare(priv->aclk);
+	}
+	dev_dbg(&priv->pdev->dev, "%s: n_active_ch %d\n", __func__,
+		atomic_read(&priv->n_active_ch));
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(stm32_dfsdm_stop_dfsdm);
+
+static int stm32_dfsdm_parse_of(struct platform_device *pdev,
+				struct dfsdm_priv *priv)
+{
+	struct device_node *node = pdev->dev.of_node;
+	struct resource *res;
+	unsigned long clk_freq;
+	unsigned int spi_freq, rem;
+	int ret;
+
+	if (!node)
+		return -EINVAL;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!res) {
+		dev_err(&pdev->dev, "Failed to get memory resource\n");
+		return -ENODEV;
+	}
+	priv->dfsdm.phys_base = res->start;
+	priv->dfsdm.base = devm_ioremap_resource(&pdev->dev, res);
+
+	/*
+	 * "dfsdm" clock is mandatory for DFSDM peripheral clocking.
+	 * "dfsdm" or "audio" clocks can be used as source clock for
+	 * the SPI clock out signal and internal processing, depending
+	 * on use case.
+	 */
+	priv->clk = devm_clk_get(&pdev->dev, "dfsdm");
+	if (IS_ERR(priv->clk)) {
+		dev_err(&pdev->dev, "No stm32_dfsdm_clk clock found\n");
+		return -EINVAL;
+	}
+
+	priv->aclk = devm_clk_get(&pdev->dev, "audio");
+	if (IS_ERR(priv->aclk))
+		priv->aclk = NULL;
+
+	if (priv->aclk)
+		clk_freq = clk_get_rate(priv->aclk);
+	else
+		clk_freq = clk_get_rate(priv->clk);
+
+	/* SPI clock out frequency */
+	ret = of_property_read_u32(pdev->dev.of_node, "spi-max-frequency",
+				   &spi_freq);
+	if (ret < 0) {
+		/* No SPI master mode */
+		return 0;
+	}
+
+	priv->spi_clk_out_div = div_u64_rem(clk_freq, spi_freq, &rem) - 1;
+	priv->dfsdm.spi_master_freq = spi_freq;
+
+	if (rem) {
+		dev_warn(&pdev->dev, "SPI clock not accurate\n");
+		dev_warn(&pdev->dev, "%ld = %d * %d + %d\n",
+			 clk_freq, spi_freq, priv->spi_clk_out_div + 1, rem);
+	}
+
+	return 0;
+};
+
+static const struct of_device_id stm32_dfsdm_of_match[] = {
+	{
+		.compatible = "st,stm32h7-dfsdm",
+		.data = &stm32h7_dfsdm_data,
+	},
+	{}
+};
+MODULE_DEVICE_TABLE(of, stm32_dfsdm_of_match);
+
+static int stm32_dfsdm_probe(struct platform_device *pdev)
+{
+	struct dfsdm_priv *priv;
+	struct device_node *pnode = pdev->dev.of_node;
+	const struct of_device_id *of_id;
+	const struct stm32_dfsdm_dev_data *dev_data;
+	struct stm32_dfsdm *dfsdm;
+	int ret;
+
+	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->pdev = pdev;
+
+	of_id = of_match_node(stm32_dfsdm_of_match, pnode);
+	if (!of_id->data) {
+		dev_err(&pdev->dev, "Data associated to device is missing\n");
+		return -EINVAL;
+	}
+
+	dev_data = (const struct stm32_dfsdm_dev_data *)of_id->data;
+	dfsdm = &priv->dfsdm;
+	dfsdm->fl_list = devm_kcalloc(&pdev->dev, dev_data->num_filters,
+				      sizeof(*dfsdm->fl_list), GFP_KERNEL);
+	if (!dfsdm->fl_list)
+		return -ENOMEM;
+
+	dfsdm->num_fls = dev_data->num_filters;
+	dfsdm->ch_list = devm_kcalloc(&pdev->dev, dev_data->num_channels,
+				      sizeof(*dfsdm->ch_list),
+				      GFP_KERNEL);
+	if (!dfsdm->ch_list)
+		return -ENOMEM;
+	dfsdm->num_chs = dev_data->num_channels;
+
+	ret = stm32_dfsdm_parse_of(pdev, priv);
+	if (ret < 0)
+		return ret;
+
+	dfsdm->regmap = devm_regmap_init_mmio_clk(&pdev->dev, "dfsdm",
+						  dfsdm->base,
+						  &stm32h7_dfsdm_regmap_cfg);
+	if (IS_ERR(dfsdm->regmap)) {
+		ret = PTR_ERR(dfsdm->regmap);
+		dev_err(&pdev->dev, "%s: Failed to allocate regmap: %d\n",
+			__func__, ret);
+		return ret;
+	}
+
+	platform_set_drvdata(pdev, dfsdm);
+
+	return devm_of_platform_populate(&pdev->dev);
+}
+
+static struct platform_driver stm32_dfsdm_driver = {
+	.probe = stm32_dfsdm_probe,
+	.driver = {
+		.name = "stm32-dfsdm",
+		.of_match_table = stm32_dfsdm_of_match,
+	},
+};
+
+module_platform_driver(stm32_dfsdm_driver);
+
+MODULE_AUTHOR("Arnaud Pouliquen <arnaud.pouliquen@st.com>");
+MODULE_DESCRIPTION("STMicroelectronics STM32 dfsdm driver");
+MODULE_LICENSE("GPL v2");