[PATCH RFC 2/2] hwmon: Add RPi PoE HAT fan driver

[Stefan Wahren]

From: Serge Schneider <serge@xxxxxxxxxxxxxxx>

This adds support for the fan located on the Raspberry Pi Power over
Ethernet HAT. The driver passes commands the Raspberry Pi firmware
through the mailbox property interface. The firmware then forwards
the commands to the board over I2C on the ID_EEPROM pins.

Signed-off-by: Serge Schneider <serge@xxxxxxxxxxxxxxx>
Signed-off-by: Stefan Wahren <stefan.wahren@xxxxxxxx>
---
 Documentation/hwmon/rpi-poe-fan            |  15 ++
 drivers/hwmon/Kconfig                      |  11 +
 drivers/hwmon/Makefile                     |   1 +
 drivers/hwmon/rpi-poe-fan.c                | 414 +++++++++++++++++++++++++++++
 include/soc/bcm2835/raspberrypi-firmware.h |   2 +
 5 files changed, 443 insertions(+)
 create mode 100644 Documentation/hwmon/rpi-poe-fan
 create mode 100644 drivers/hwmon/rpi-poe-fan.c

diff --git a/Documentation/hwmon/rpi-poe-fan b/Documentation/hwmon/rpi-poe-fan
new file mode 100644
index 0000000..9182ab6
--- /dev/null
+++ b/Documentation/hwmon/rpi-poe-fan
@@ -0,0 +1,15 @@
+Kernel driver rpi-poe-fan
+=====================
+
+This driver enables the use of the Raspberry Pi PoE HAT fan.
+
+Author: Serge Schneider <serge@xxxxxxxxxxxxxxx>
+
+Description
+-----------
+
+The driver implements a simple interface for driving the Raspberry Pi PoE
+(Power over Ethernet) HAT fan. The driver passes commands to the Raspberry Pi
+firmware through the mailbox property interface. The firmware then forwards
+the commands to the board over I2C on the ID_EEPROM pins. The driver exposes
+the fan to the user space through the hwmon sysfs interface.
diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index 81da17a..f8b5572 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -1330,6 +1330,17 @@ config SENSORS_RASPBERRYPI_HWMON
 	  This driver can also be built as a module. If so, the module
 	  will be called raspberrypi-hwmon.
 
+config SENSORS_RPI_POE_FAN
+	tristate "Raspberry Pi PoE HAT fan"
+	depends on RASPBERRYPI_FIRMWARE || (COMPILE_TEST && !RASPBERRYPI_FIRMWARE)
+	depends on THERMAL || THERMAL=n
+	help
+	  If you say yes here you get support for Raspberry Pi PoE (Power over
+	  Ethernet) HAT fan.
+
+	  This driver can also be built as a module.  If so, the module
+	  will be called rpi-poe-fan.
+
 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 93f7f41..3e2a504 100644
--- a/drivers/hwmon/Makefile
+++ b/drivers/hwmon/Makefile
@@ -144,6 +144,7 @@ obj-$(CONFIG_SENSORS_PCF8591)	+= pcf8591.o
 obj-$(CONFIG_SENSORS_POWR1220)  += powr1220.o
 obj-$(CONFIG_SENSORS_PWM_FAN)	+= pwm-fan.o
 obj-$(CONFIG_SENSORS_RASPBERRYPI_HWMON)	+= raspberrypi-hwmon.o
+obj-$(CONFIG_SENSORS_RPI_POE_FAN)	+= rpi-poe-fan.o
 obj-$(CONFIG_SENSORS_S3C)	+= s3c-hwmon.o
 obj-$(CONFIG_SENSORS_SCH56XX_COMMON)+= sch56xx-common.o
 obj-$(CONFIG_SENSORS_SCH5627)	+= sch5627.o
diff --git a/drivers/hwmon/rpi-poe-fan.c b/drivers/hwmon/rpi-poe-fan.c
new file mode 100644
index 0000000..192afa4
--- /dev/null
+++ b/drivers/hwmon/rpi-poe-fan.c
@@ -0,0 +1,414 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * rpi-poe-fan.c - Hwmon driver for Raspberry Pi PoE HAT fan.
+ *
+ * Copyright (C) 2018 Raspberry Pi (Trading) Ltd.
+ * Based on pwm-fan.c by Kamil Debski <k.debski@xxxxxxxxxxx>
+ *
+ * Author: Serge Schneider <serge@xxxxxxxxxxxxxxx>
+ */
+
+#include <linux/hwmon.h>
+#include <linux/hwmon-sysfs.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/sysfs.h>
+#include <linux/thermal.h>
+#include <soc/bcm2835/raspberrypi-firmware.h>
+
+#define MAX_PWM 255
+
+#define POE_CUR_PWM 0x0
+#define POE_DEF_PWM 0x1
+
+struct rpi_poe_fan_ctx {
+	struct mutex lock;
+	struct rpi_firmware *fw;
+	unsigned int pwm_value;
+	unsigned int def_pwm_value;
+	unsigned int rpi_poe_fan_state;
+	unsigned int rpi_poe_fan_max_state;
+	unsigned int *rpi_poe_fan_cooling_levels;
+	struct thermal_cooling_device *cdev;
+};
+
+struct fw_tag_data_s {
+	u32 reg;
+	u32 val;
+	u32 ret;
+};
+
+static int write_reg(struct rpi_firmware *fw, u32 reg, u32 *val)
+{
+	struct fw_tag_data_s fw_tag_data = {
+		.reg = reg,
+		.val = *val
+	};
+	int ret;
+
+	ret = rpi_firmware_property(fw, RPI_FIRMWARE_SET_POE_HAT_VAL,
+				    &fw_tag_data, sizeof(fw_tag_data));
+	if (ret)
+		return ret;
+	else if (fw_tag_data.ret)
+		return -EIO;
+
+	return 0;
+}
+
+static int read_reg(struct rpi_firmware *fw, u32 reg, u32 *val)
+{
+	struct fw_tag_data_s fw_tag_data = {
+		.reg = reg,
+	};
+	int ret;
+
+	ret = rpi_firmware_property(fw, RPI_FIRMWARE_GET_POE_HAT_VAL,
+				    &fw_tag_data, sizeof(fw_tag_data));
+	if (ret)
+		return ret;
+	else if (fw_tag_data.ret)
+		return -EIO;
+
+	*val = fw_tag_data.val;
+	return 0;
+}
+
+static int  __set_pwm(struct rpi_poe_fan_ctx *ctx, u32 pwm)
+{
+	int ret = 0;
+
+	mutex_lock(&ctx->lock);
+	if (ctx->pwm_value == pwm)
+		goto exit_set_pwm_err;
+
+	ret = write_reg(ctx->fw, POE_CUR_PWM, &pwm);
+	if (!ret)
+		ctx->pwm_value = pwm;
+exit_set_pwm_err:
+	mutex_unlock(&ctx->lock);
+	return ret;
+}
+
+static int  __set_def_pwm(struct rpi_poe_fan_ctx *ctx, u32 def_pwm)
+{
+	int ret = 0;
+
+	mutex_lock(&ctx->lock);
+	if (ctx->def_pwm_value == def_pwm)
+		goto exit_set_def_pwm_err;
+
+	ret = write_reg(ctx->fw, POE_CUR_PWM, &def_pwm);
+	if (!ret)
+		ctx->def_pwm_value = def_pwm;
+exit_set_def_pwm_err:
+	mutex_unlock(&ctx->lock);
+	return ret;
+}
+
+static void rpi_poe_fan_update_state(struct rpi_poe_fan_ctx *ctx,
+				     unsigned long pwm)
+{
+	int i;
+
+	for (i = 0; i < ctx->rpi_poe_fan_max_state; ++i)
+		if (pwm < ctx->rpi_poe_fan_cooling_levels[i + 1])
+			break;
+
+	ctx->rpi_poe_fan_state = i;
+}
+
+static ssize_t set_pwm(struct device *dev, struct device_attribute *attr,
+		       const char *buf, size_t count)
+{
+	struct rpi_poe_fan_ctx *ctx = dev_get_drvdata(dev);
+	unsigned long pwm;
+	int ret;
+
+	if (kstrtoul(buf, 10, &pwm) || pwm > MAX_PWM)
+		return -EINVAL;
+
+	ret = __set_pwm(ctx, pwm);
+	if (ret)
+		return ret;
+
+	rpi_poe_fan_update_state(ctx, pwm);
+	return count;
+}
+
+static ssize_t set_def_pwm(struct device *dev, struct device_attribute *attr,
+			   const char *buf, size_t count)
+{
+	struct rpi_poe_fan_ctx *ctx = dev_get_drvdata(dev);
+	unsigned long def_pwm;
+	int ret;
+
+	if (kstrtoul(buf, 10, &def_pwm) || def_pwm > MAX_PWM)
+		return -EINVAL;
+
+	ret = __set_def_pwm(ctx, def_pwm);
+	if (ret)
+		return ret;
+	return count;
+}
+
+static ssize_t show_pwm(struct device *dev,
+			struct device_attribute *attr, char *buf)
+{
+	struct rpi_poe_fan_ctx *ctx = dev_get_drvdata(dev);
+
+	return sprintf(buf, "%u\n", ctx->pwm_value);
+}
+
+static ssize_t show_def_pwm(struct device *dev,
+			struct device_attribute *attr, char *buf)
+{
+	struct rpi_poe_fan_ctx *ctx = dev_get_drvdata(dev);
+
+	return sprintf(buf, "%u\n", ctx->def_pwm_value);
+}
+
+
+static SENSOR_DEVICE_ATTR(pwm1, 0644, show_pwm, set_pwm, 0);
+static SENSOR_DEVICE_ATTR(def_pwm1, 0644, show_def_pwm, set_def_pwm, 1);
+
+static struct attribute *rpi_poe_fan_attrs[] = {
+	&sensor_dev_attr_pwm1.dev_attr.attr,
+	&sensor_dev_attr_def_pwm1.dev_attr.attr,
+	NULL,
+};
+
+ATTRIBUTE_GROUPS(rpi_poe_fan);
+
+/* thermal cooling device callbacks */
+static int rpi_poe_fan_get_max_state(struct thermal_cooling_device *cdev,
+				     unsigned long *state)
+{
+	struct rpi_poe_fan_ctx *ctx = cdev->devdata;
+
+	if (!ctx)
+		return -EINVAL;
+
+	*state = ctx->rpi_poe_fan_max_state;
+
+	return 0;
+}
+
+static int rpi_poe_fan_get_cur_state(struct thermal_cooling_device *cdev,
+				     unsigned long *state)
+{
+	struct rpi_poe_fan_ctx *ctx = cdev->devdata;
+
+	if (!ctx)
+		return -EINVAL;
+
+	*state = ctx->rpi_poe_fan_state;
+
+	return 0;
+}
+
+static int rpi_poe_fan_set_cur_state(struct thermal_cooling_device *cdev,
+				     unsigned long state)
+{
+	struct rpi_poe_fan_ctx *ctx = cdev->devdata;
+	int ret;
+
+	if (!ctx || (state > ctx->rpi_poe_fan_max_state))
+		return -EINVAL;
+
+	if (state == ctx->rpi_poe_fan_state)
+		return 0;
+
+	ret = __set_pwm(ctx, ctx->rpi_poe_fan_cooling_levels[state]);
+	if (ret) {
+		dev_err(&cdev->device, "Cannot set pwm!\n");
+		return ret;
+	}
+
+	ctx->rpi_poe_fan_state = state;
+
+	return ret;
+}
+
+static const struct thermal_cooling_device_ops rpi_poe_fan_cooling_ops = {
+	.get_max_state = rpi_poe_fan_get_max_state,
+	.get_cur_state = rpi_poe_fan_get_cur_state,
+	.set_cur_state = rpi_poe_fan_set_cur_state,
+};
+
+static int rpi_poe_fan_of_get_cooling_data(struct device *dev,
+				       struct rpi_poe_fan_ctx *ctx)
+{
+	struct device_node *np = dev->of_node;
+	int num, i, ret;
+
+	if (!of_find_property(np, "cooling-levels", NULL))
+		return 0;
+
+	ret = of_property_count_u32_elems(np, "cooling-levels");
+	if (ret <= 0) {
+		dev_err(dev, "cooling-levels property missing or invalid: %d\n",
+			ret);
+		return ret ? : -EINVAL;
+	}
+
+	num = ret;
+	ctx->rpi_poe_fan_cooling_levels = devm_kzalloc(dev, num * sizeof(u32),
+						   GFP_KERNEL);
+	if (!ctx->rpi_poe_fan_cooling_levels)
+		return -ENOMEM;
+
+	ret = of_property_read_u32_array(np, "cooling-levels",
+					 ctx->rpi_poe_fan_cooling_levels, num);
+	if (ret) {
+		dev_err(dev, "Property 'cooling-levels' cannot be read!\n");
+		return ret;
+	}
+
+	for (i = 0; i < num; i++) {
+		if (ctx->rpi_poe_fan_cooling_levels[i] > MAX_PWM) {
+			dev_err(dev, "PWM fan state[%d]:%d > %d\n", i,
+				ctx->rpi_poe_fan_cooling_levels[i], MAX_PWM);
+			return -EINVAL;
+		}
+	}
+
+	ctx->rpi_poe_fan_max_state = num - 1;
+
+	return 0;
+}
+
+static int rpi_poe_fan_probe(struct platform_device *pdev)
+{
+	struct thermal_cooling_device *cdev;
+	struct rpi_poe_fan_ctx *ctx;
+	struct device *hwmon;
+	struct device_node *np = pdev->dev.of_node;
+	struct device_node *fw_node;
+	int ret;
+
+	fw_node = of_parse_phandle(np, "firmware", 0);
+	if (!fw_node) {
+		dev_err(&pdev->dev, "Missing firmware node\n");
+		return -ENOENT;
+	}
+
+	ctx = devm_kzalloc(&pdev->dev, sizeof(*ctx), GFP_KERNEL);
+	if (!ctx)
+		return -ENOMEM;
+
+	mutex_init(&ctx->lock);
+
+	ctx->fw = rpi_firmware_get(fw_node);
+	if (!ctx->fw)
+		return -EPROBE_DEFER;
+
+	platform_set_drvdata(pdev, ctx);
+
+	ret = read_reg(ctx->fw, POE_DEF_PWM, &ctx->def_pwm_value);
+	if (ret) {
+		dev_err(&pdev->dev, "Failed to get default PWM value: %i\n",
+			ret);
+		return ret;
+	}
+	ret = read_reg(ctx->fw, POE_CUR_PWM, &ctx->pwm_value);
+	if (ret) {
+		dev_err(&pdev->dev, "Failed to get current PWM value: %i\n",
+			ret);
+		return ret;
+	}
+
+	hwmon = devm_hwmon_device_register_with_groups(&pdev->dev, "rpipoefan",
+						       ctx, rpi_poe_fan_groups);
+	if (IS_ERR(hwmon)) {
+		dev_err(&pdev->dev, "Failed to register hwmon device\n");
+		return PTR_ERR(hwmon);
+	}
+
+	ret = rpi_poe_fan_of_get_cooling_data(&pdev->dev, ctx);
+	if (ret)
+		return ret;
+
+	rpi_poe_fan_update_state(ctx, ctx->pwm_value);
+	if (!IS_ENABLED(CONFIG_THERMAL))
+		return 0;
+
+	cdev = thermal_of_cooling_device_register(np,
+						  "rpi-poe-fan", ctx,
+						  &rpi_poe_fan_cooling_ops);
+	if (IS_ERR(cdev)) {
+		dev_err(&pdev->dev,
+			"Failed to register rpi-poe-fan as cooling device");
+		return PTR_ERR(cdev);
+	}
+	ctx->cdev = cdev;
+	thermal_cdev_update(cdev);
+
+	return 0;
+}
+
+static int rpi_poe_fan_remove(struct platform_device *pdev)
+{
+	struct rpi_poe_fan_ctx *ctx = platform_get_drvdata(pdev);
+	u32 value = ctx->def_pwm_value;
+
+	thermal_cooling_device_unregister(ctx->cdev);
+	if (ctx->pwm_value != value)
+		write_reg(ctx->fw, POE_CUR_PWM, &value);
+
+	return 0;
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int rpi_poe_fan_suspend(struct device *dev)
+{
+	struct rpi_poe_fan_ctx *ctx = dev_get_drvdata(dev);
+	u32 value = 0;
+	int ret = 0;
+
+	if (ctx->pwm_value != value)
+		ret = write_reg(ctx->fw, POE_CUR_PWM, &value);
+
+	return ret;
+}
+
+static int rpi_poe_fan_resume(struct device *dev)
+{
+	struct rpi_poe_fan_ctx *ctx = dev_get_drvdata(dev);
+	u32 value = ctx->pwm_value;
+	int ret = 0;
+
+	if (value != 0)
+		ret = write_reg(ctx->fw, POE_CUR_PWM, &value);
+
+	return ret;
+}
+#endif
+
+static SIMPLE_DEV_PM_OPS(rpi_poe_fan_pm, rpi_poe_fan_suspend,
+			 rpi_poe_fan_resume);
+
+static const struct of_device_id of_rpi_poe_fan_match[] = {
+	{ .compatible = "raspberrypi,rpi-poe-fan", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, of_rpi_poe_fan_match);
+
+static struct platform_driver rpi_poe_fan_driver = {
+	.probe		= rpi_poe_fan_probe,
+	.remove		= rpi_poe_fan_remove,
+	.driver	= {
+		.name		= "rpi-poe-fan",
+		.pm		= &rpi_poe_fan_pm,
+		.of_match_table	= of_rpi_poe_fan_match,
+	},
+};
+
+module_platform_driver(rpi_poe_fan_driver);
+
+MODULE_AUTHOR("Serge Schneider <serge@xxxxxxxxxxxxxxx>");
+MODULE_ALIAS("platform:rpi-poe-fan");
+MODULE_DESCRIPTION("Raspberry Pi PoE HAT fan driver");
+MODULE_LICENSE("GPL");
diff --git a/include/soc/bcm2835/raspberrypi-firmware.h b/include/soc/bcm2835/raspberrypi-firmware.h
index c4a5c9e..f70d08a 100644
--- a/include/soc/bcm2835/raspberrypi-firmware.h
+++ b/include/soc/bcm2835/raspberrypi-firmware.h
@@ -89,6 +89,8 @@ enum rpi_firmware_property_tag {
 	RPI_FIRMWARE_SET_GPIO_CONFIG =                        0x00038043,
 	RPI_FIRMWARE_GET_PERIPH_REG =                         0x00030045,
 	RPI_FIRMWARE_SET_PERIPH_REG =                         0x00038045,
+	RPI_FIRMWARE_GET_POE_HAT_VAL =                        0x00030049,
+	RPI_FIRMWARE_SET_POE_HAT_VAL =                        0x00030050,
 
 
 	/* Dispmanx TAGS */
-- 
2.7.4