thermal: Add support for the MCU controlled FAN on Khadas boards

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

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

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Reviewed-by: Amit Kucheria <amit.kucheria@linaro.org>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

drivers/thermal/Kconfig

@@ -500,4 +500,15 @@ config SPRD_THERMAL
 	help
 	  Support for the Spreadtrum thermal sensor driver in the Linux thermal
 	  framework.
+
+config KHADAS_MCU_FAN_THERMAL
+	tristate "Khadas MCU controller FAN cooling support"
+	depends on OF || COMPILE_TEST
+	depends on MFD_KHADAS_MCU
+	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.
+
 endif

drivers/thermal/Makefile

@@ -61,3 +61,4 @@ obj-$(CONFIG_ZX2967_THERMAL)	+= zx2967_thermal.o
 obj-$(CONFIG_UNIPHIER_THERMAL)	+= uniphier_thermal.o
 obj-$(CONFIG_AMLOGIC_THERMAL)     += amlogic_thermal.o
 obj-$(CONFIG_SPRD_THERMAL)	+= sprd_thermal.o
+obj-$(CONFIG_KHADAS_MCU_FAN_THERMAL)	+= khadas_mcu_fan.o

drivers/thermal/khadas_mcu_fan.c

@@ -0,0 +1,162 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Khadas MCU Controlled FAN driver
+ *
+ * Copyright (C) 2020 BayLibre SAS
+ * Author(s): Neil Armstrong <narmstrong@baylibre.com>
+ */
+
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.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->regmap, KHADAS_MCU_CMD_FAN_STATUS_CTRL_REG,
+			   level);
+	if (ret)
+		return ret;
+
+	ctx->level = level;
+
+	return 0;
+}
+
+static int khadas_mcu_fan_get_max_state(struct thermal_cooling_device *cdev,
+					unsigned long *state)
+{
+	*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;
+
+	*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 (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;
+	int ret;
+
+	ctx = devm_kzalloc(dev, sizeof(*ctx), GFP_KERNEL);
+	if (!ctx)
+		return -ENOMEM;
+	ctx->mcu = mcu;
+	platform_set_drvdata(pdev, ctx);
+
+	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 void khadas_mcu_fan_shutdown(struct platform_device *pdev)
+{
+	struct khadas_mcu_fan_ctx *ctx = platform_get_drvdata(pdev);
+
+	khadas_mcu_fan_set_level(ctx, 0);
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int khadas_mcu_fan_suspend(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 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@baylibre.com>");
+MODULE_DESCRIPTION("Khadas MCU FAN driver");
+MODULE_LICENSE("GPL");