[RFC 3/8] hwmon: add support for the MCU controlled FAN on Khadas boards

[Neil Armstrong]

The new Khadas VIM2 and VIM3 boards controls the cooling fan via the
on-board microcontroller.

This implements the FAN control as HWMON devices as cell of the Khadas
MCU MFD driver.

Signed-off-by: Neil Armstrong <narmstrong@xxxxxxxxxxxx>
---
 drivers/hwmon/Kconfig          |   9 ++
 drivers/hwmon/Makefile         |   1 +
 drivers/hwmon/khadas-mcu-fan.c | 230 +++++++++++++++++++++++++++++++++
 3 files changed, 240 insertions(+)
 create mode 100644 drivers/hwmon/khadas-mcu-fan.c

diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index 4c62f900bf7e..7f63ff7bb732 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -1997,6 +1997,15 @@ config SENSORS_XGENE
 	  If you say yes here you get support for the temperature
 	  and power sensors for APM X-Gene SoC.
 
+config SENSORS_KHADAS_MCU_FAN
+	tristate "Khadas MCU controller FAN driver"
+	depends on OF || COMPILE_TEST
+	select MFD_CORE
+	select REGMAP
+	help
+	  If you say yes here you get support for the FAN controlled
+	  by the Microcontroller found on the Khadas VIM boards.
+
 if ACPI
 
 comment "ACPI drivers"
diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
index b0b9c8e57176..20db40f6d57f 100644
--- a/drivers/hwmon/Makefile
+++ b/drivers/hwmon/Makefile
@@ -185,6 +185,7 @@ obj-$(CONFIG_SENSORS_W83L786NG)	+= w83l786ng.o
 obj-$(CONFIG_SENSORS_WM831X)	+= wm831x-hwmon.o
 obj-$(CONFIG_SENSORS_WM8350)	+= wm8350-hwmon.o
 obj-$(CONFIG_SENSORS_XGENE)	+= xgene-hwmon.o
+obj-$(CONFIG_SENSORS_KHADAS_MCU_FAN)	+= khadas-mcu-fan.o
 
 obj-$(CONFIG_SENSORS_OCC)	+= occ/
 obj-$(CONFIG_PMBUS)		+= pmbus/
diff --git a/drivers/hwmon/khadas-mcu-fan.c b/drivers/hwmon/khadas-mcu-fan.c
new file mode 100644
index 000000000000..dd92b2bcb7e3
--- /dev/null
+++ b/drivers/hwmon/khadas-mcu-fan.c
@@ -0,0 +1,230 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Khadas MCU Controlled FAN driver
+ *
+ * Copyright (C) 2020 BayLibre SAS
+ * Author(s): Neil Armstrong <narmstrong@xxxxxxxxxxxx>
+ */
+
+#include <linux/hwmon.h>
+#include <linux/hwmon-sysfs.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/regulator/consumer.h>
+#include <linux/mfd/khadas-mcu.h>
+#include <linux/regmap.h>
+#include <linux/sysfs.h>
+#include <linux/thermal.h>
+
+#define MAX_LEVEL 3
+
+struct khadas_mcu_fan_ctx {
+	struct khadas_mcu *mcu;
+	unsigned int level;
+	struct thermal_cooling_device *cdev;
+};
+
+static int khadas_mcu_fan_set_level(struct khadas_mcu_fan_ctx *ctx,
+				    unsigned int level)
+{
+	int ret;
+
+	ret = regmap_write(ctx->mcu->map, KHADAS_MCU_CMD_FAN_STATUS_CTRL_REG,
+			   level);
+	if (ret)
+		return ret;
+
+	ctx->level = level;
+
+	return 0;
+}
+
+static ssize_t level_store(struct device *dev, struct device_attribute *attr,
+			   const char *buf, size_t count)
+{
+	struct khadas_mcu_fan_ctx *ctx = dev_get_drvdata(dev);
+	unsigned long level;
+	int ret;
+
+	if (kstrtoul(buf, 10, &level) || level > MAX_LEVEL)
+		return -EINVAL;
+
+	ret = khadas_mcu_fan_set_level(ctx, level);
+	if (ret < 0)
+		return ret;
+
+	return count;
+}
+
+static ssize_t level_show(struct device *dev, struct device_attribute *attr,
+			  char *buf)
+{
+	struct khadas_mcu_fan_ctx *ctx = dev_get_drvdata(dev);
+
+	return sprintf(buf, "%u\n", ctx->level);
+}
+
+static SENSOR_DEVICE_ATTR_RW(level1, level, 0);
+
+static struct attribute *khadas_mcu_fan_attrs[] = {
+	&sensor_dev_attr_level1.dev_attr.attr,
+	NULL,
+};
+
+static const struct attribute_group khadas_mcu_fan_group = {
+	.attrs = khadas_mcu_fan_attrs,
+};
+
+static const struct attribute_group *khadas_mcu_fan_groups[] = {
+	&khadas_mcu_fan_group,
+	NULL,
+};
+
+/* thermal cooling device callbacks */
+static int khadas_mcu_fan_get_max_state(struct thermal_cooling_device *cdev,
+					unsigned long *state)
+{
+	struct khadas_mcu_fan_ctx *ctx = cdev->devdata;
+
+	if (!ctx)
+		return -EINVAL;
+
+	*state = MAX_LEVEL;
+
+	return 0;
+}
+
+static int khadas_mcu_fan_get_cur_state(struct thermal_cooling_device *cdev,
+					unsigned long *state)
+{
+	struct khadas_mcu_fan_ctx *ctx = cdev->devdata;
+
+	if (!ctx)
+		return -EINVAL;
+
+	*state = ctx->level;
+
+	return 0;
+}
+
+static int
+khadas_mcu_fan_set_cur_state(struct thermal_cooling_device *cdev,
+			     unsigned long state)
+{
+	struct khadas_mcu_fan_ctx *ctx = cdev->devdata;
+
+	if (!ctx || (state > MAX_LEVEL))
+		return -EINVAL;
+
+	if (state == ctx->level)
+		return 0;
+
+	return khadas_mcu_fan_set_level(ctx, state);
+}
+
+static const struct thermal_cooling_device_ops khadas_mcu_fan_cooling_ops = {
+	.get_max_state = khadas_mcu_fan_get_max_state,
+	.get_cur_state = khadas_mcu_fan_get_cur_state,
+	.set_cur_state = khadas_mcu_fan_set_cur_state,
+};
+
+static int khadas_mcu_fan_probe(struct platform_device *pdev)
+{
+	struct khadas_mcu *mcu = dev_get_drvdata(pdev->dev.parent);
+	struct thermal_cooling_device *cdev;
+	struct device *dev = &pdev->dev;
+	struct khadas_mcu_fan_ctx *ctx;
+	struct device *hwmon;
+	int ret;
+
+	ctx = devm_kzalloc(dev, sizeof(*ctx), GFP_KERNEL);
+	if (!ctx)
+		return -ENOMEM;
+	ctx->mcu = mcu;
+	platform_set_drvdata(pdev, ctx);
+
+	hwmon = devm_hwmon_device_register_with_groups(dev, "khadas-mcu-fan",
+						       ctx,
+						       khadas_mcu_fan_groups);
+	if (IS_ERR(hwmon)) {
+		dev_err(dev, "Failed to register hwmon device\n");
+		return PTR_ERR(hwmon);
+	}
+
+	if (IS_ENABLED(CONFIG_THERMAL)) {
+		cdev = devm_thermal_of_cooling_device_register(dev->parent,
+			dev->parent->of_node, "khadas-mcu-fan", ctx,
+			&khadas_mcu_fan_cooling_ops);
+		if (IS_ERR(cdev)) {
+			ret = PTR_ERR(cdev);
+			dev_err(dev,
+				"Failed to register khadas-mcu-fan as cooling device: %d\n",
+				ret);
+			return ret;
+		}
+		ctx->cdev = cdev;
+		thermal_cdev_update(cdev);
+	}
+
+	return 0;
+}
+
+static int khadas_mcu_fan_disable(struct device *dev)
+{
+	struct khadas_mcu_fan_ctx *ctx = dev_get_drvdata(dev);
+	unsigned int level_save = ctx->level;
+	int ret;
+
+	ret = khadas_mcu_fan_set_level(ctx, 0);
+	if (ret)
+		return ret;
+
+	ctx->level = level_save;
+
+	return 0;
+}
+
+static void khadas_mcu_fan_shutdown(struct platform_device *pdev)
+{
+	khadas_mcu_fan_disable(&pdev->dev);
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int khadas_mcu_fan_suspend(struct device *dev)
+{
+	return khadas_mcu_fan_disable(dev);
+}
+
+static int khadas_mcu_fan_resume(struct device *dev)
+{
+	struct khadas_mcu_fan_ctx *ctx = dev_get_drvdata(dev);
+
+	return khadas_mcu_fan_set_level(ctx, ctx->level);
+}
+#endif
+
+static SIMPLE_DEV_PM_OPS(khadas_mcu_fan_pm, khadas_mcu_fan_suspend,
+			 khadas_mcu_fan_resume);
+
+static const struct platform_device_id khadas_mcu_fan_id_table[] = {
+	{ .name = "khadas-mcu-fan-ctrl", },
+	{},
+};
+MODULE_DEVICE_TABLE(platform, khadas_mcu_fan_id_table);
+
+static struct platform_driver khadas_mcu_fan_driver = {
+	.probe		= khadas_mcu_fan_probe,
+	.shutdown	= khadas_mcu_fan_shutdown,
+	.driver	= {
+		.name		= "khadas-mcu-fan-ctrl",
+		.pm		= &khadas_mcu_fan_pm,
+	},
+	.id_table	= khadas_mcu_fan_id_table,
+};
+
+module_platform_driver(khadas_mcu_fan_driver);
+
+MODULE_AUTHOR("Neil Armstrong <narmstrong@xxxxxxxxxxxx>");
+MODULE_DESCRIPTION("Khadas MCU FAN driver");
+MODULE_LICENSE("GPL");
-- 
2.22.0