[v2,12/16] hwmon: add support for the sl28cpld hardware monitoring controller

diff --git a/Documentation/hwmon/sl28cpld.rst b/Documentation/hwmon/sl28cpld.rst
new file mode 100644
index 000000000000..7ed65f78250c
--- /dev/null
+++ b/Documentation/hwmon/sl28cpld.rst
@@ -0,0 +1,36 @@ 
+.. SPDX-License-Identifier: GPL-2.0-only
+
+Kernel driver sl28cpld
+======================
+
+Supported chips:
+
+   * Kontron sl28cpld
+
+     Prefix: 'sl28cpld'
+
+     Datasheet: not available
+
+Authors: Michael Walle <michael@walle.cc>
+
+Description
+-----------
+
+The sl28cpld is a board management controller which also exposes a hardware
+monitoring controller. At the moment this controller supports a single fan
+supervisor. In the future there might be other flavours and additional
+hardware monitoring might be supported.
+
+The fan supervisor has a 7 bit counter register and a counter period of 1
+second. If the 7 bit counter overflows, the supervisor will automatically
+switch to x8 mode to support a wider input range at the loss of
+granularity.
+
+Sysfs entries
+-------------
+
+The following attributes are supported.
+
+======================= ========================================================
+fan1_input		Fan RPM. Assuming 2 pulses per revolution.
+======================= ========================================================
diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index 05a30832c6ba..c98716f78cfa 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -1412,6 +1412,16 @@  config SENSORS_RASPBERRYPI_HWMON
 	  This driver can also be built as a module. If so, the module
 	  will be called raspberrypi-hwmon.
 
+config SENSORS_SL28CPLD
+	tristate "Kontron's SMARC-sAL28 hardware monitoring driver"
+	depends on MFD_SL28CPLD
+	help
+	  If you say yes here you get support for a fan connected to the
+	  input of the SMARC connector of Kontron's SMARC-sAL28 module.
+
+	  This driver can also be built as a module.  If so, the module
+	  will be called sl28cpld-hwmon.
+
 config SENSORS_SHT15
 	tristate "Sensiron humidity and temperature sensors. SHT15 and compat."
 	depends on GPIOLIB || COMPILE_TEST
diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
index b0b9c8e57176..dfb0f8cda2dd 100644
--- a/drivers/hwmon/Makefile
+++ b/drivers/hwmon/Makefile
@@ -155,6 +155,7 @@  obj-$(CONFIG_SENSORS_S3C)	+= s3c-hwmon.o
 obj-$(CONFIG_SENSORS_SCH56XX_COMMON)+= sch56xx-common.o
 obj-$(CONFIG_SENSORS_SCH5627)	+= sch5627.o
 obj-$(CONFIG_SENSORS_SCH5636)	+= sch5636.o
+obj-$(CONFIG_SENSORS_SL28CPLD)	+= sl28cpld-hwmon.o
 obj-$(CONFIG_SENSORS_SHT15)	+= sht15.o
 obj-$(CONFIG_SENSORS_SHT21)	+= sht21.o
 obj-$(CONFIG_SENSORS_SHT3x)	+= sht3x.o
diff --git a/drivers/hwmon/sl28cpld-hwmon.c b/drivers/hwmon/sl28cpld-hwmon.c
new file mode 100644
index 000000000000..c79bdfed8332
--- /dev/null
+++ b/drivers/hwmon/sl28cpld-hwmon.c
@@ -0,0 +1,151 @@ 
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * sl28cpld hardware monitoring driver.
+ *
+ * Copyright 2019 Kontron Europe GmbH
+ */
+
+#include <linux/bitfield.h>
+#include <linux/hwmon.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+
+#define FAN_INPUT		0x00
+#define   FAN_SCALE_X8		BIT(7)
+#define   FAN_VALUE_MASK	GENMASK(6, 0)
+
+struct sl28cpld_hwmon {
+	struct regmap *regmap;
+	u32 offset;
+};
+
+static umode_t sl28cpld_hwmon_is_visible(const void *data,
+					 enum hwmon_sensor_types type,
+					 u32 attr, int channel)
+{
+	return 0444;
+}
+
+static int sl28cpld_hwmon_read(struct device *dev,
+			       enum hwmon_sensor_types type, u32 attr,
+			       int channel, long *input)
+{
+	struct sl28cpld_hwmon *hwmon = dev_get_drvdata(dev);
+	unsigned int value;
+	int ret;
+
+	switch (attr) {
+	case hwmon_fan_input:
+		ret = regmap_read(hwmon->regmap, hwmon->offset + FAN_INPUT,
+				  &value);
+		if (ret)
+			return ret;
+		/*
+		 * The register has a 7 bit value and 1 bit which indicates the
+		 * scale. If the MSB is set, then the lower 7 bit has to be
+		 * multiplied by 8, to get the correct reading.
+		 */
+		if (value & FAN_SCALE_X8)
+			value = FIELD_GET(FAN_VALUE_MASK, value) << 3;
+
+		/*
+		 * The counter period is 1000ms and the sysfs specification
+		 * says we should asssume 2 pulses per revolution.
+		 */
+		value *= 60 / 2;
+
+		break;
+	default:
+		return -EOPNOTSUPP;
+	}
+
+	*input = value;
+	return 0;
+}
+
+static const u32 sl28cpld_hwmon_fan_config[] = {
+	HWMON_F_INPUT,
+	0
+};
+
+static const struct hwmon_channel_info sl28cpld_hwmon_fan = {
+	.type = hwmon_fan,
+	.config = sl28cpld_hwmon_fan_config,
+};
+
+static const struct hwmon_channel_info *sl28cpld_hwmon_info[] = {
+	&sl28cpld_hwmon_fan,
+	NULL
+};
+
+static const struct hwmon_ops sl28cpld_hwmon_ops = {
+	.is_visible = sl28cpld_hwmon_is_visible,
+	.read = sl28cpld_hwmon_read,
+};
+
+static const struct hwmon_chip_info sl28cpld_hwmon_chip_info = {
+	.ops = &sl28cpld_hwmon_ops,
+	.info = sl28cpld_hwmon_info,
+};
+
+static int sl28cpld_hwmon_probe(struct platform_device *pdev)
+{
+	struct device *hwmon_dev;
+	struct sl28cpld_hwmon *hwmon;
+	struct resource *res;
+
+	if (!pdev->dev.parent)
+		return -ENODEV;
+
+	hwmon = devm_kzalloc(&pdev->dev, sizeof(*hwmon), GFP_KERNEL);
+	if (!hwmon)
+		return -ENOMEM;
+
+	hwmon->regmap = dev_get_regmap(pdev->dev.parent, NULL);
+	if (!hwmon->regmap)
+		return -ENODEV;
+
+	res = platform_get_resource(pdev, IORESOURCE_REG, 0);
+	if (!res)
+		return -EINVAL;
+	hwmon->offset = res->start;
+
+	hwmon_dev = devm_hwmon_device_register_with_info(&pdev->dev,
+				"sl28cpld_hwmon", hwmon,
+				&sl28cpld_hwmon_chip_info, NULL);
+	if (IS_ERR(hwmon_dev)) {
+		dev_err(&pdev->dev, "failed to register as hwmon device");
+		return PTR_ERR(hwmon_dev);
+	}
+
+	return 0;
+}
+
+static const struct of_device_id sl28cpld_hwmon_of_match[] = {
+	{ .compatible = "kontron,sl28cpld-fan" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, sl28cpld_hwmon_of_match);
+
+static const struct platform_device_id sl28cpld_hwmon_id_table[] = {
+	{ "sl28cpld-fan" },
+	{}
+};
+MODULE_DEVICE_TABLE(platform, sl28cpld_hwmon_id_table);
+
+static struct platform_driver sl28cpld_hwmon_driver = {
+	.probe = sl28cpld_hwmon_probe,
+	.id_table = sl28cpld_hwmon_id_table,
+	.driver = {
+		.name = KBUILD_MODNAME,
+		.of_match_table = sl28cpld_hwmon_of_match,
+	},
+};
+module_platform_driver(sl28cpld_hwmon_driver);
+
+MODULE_DESCRIPTION("sl28cpld Hardware Monitoring Driver");
+MODULE_AUTHOR("Michael Walle <michael@walle.cc>");
+MODULE_LICENSE("GPL");