[PATCH 3/3] hwmon: cros-ec-hwmon: Add Chromium-EC HWMON driver

[Moritz Fischer <moritz.fischer@ettus.com>]

From: Moritz Fischer <mdf@kernel.org>

This adds a hwmon driver for the Chromium EC's fans
and temperature sensors.

Signed-off-by: Moritz Fischer <mdf@kernel.org>
---

This one still needs some work, but I figured some early feedback might not hurt.
Specifically I was wondering if using the devm_hwmon_register_with_info() is
preferable to the devm_hwmon_register_with_groups().

The EC has a bunch of additional features such as setting thermal limits etc,
which I'd still like to add but I figured I'll get some feedback on what I got so far.

Thanks,

Moritz

---
 drivers/hwmon/Kconfig         |   8 ++
 drivers/hwmon/Makefile        |   1 +
 drivers/hwmon/cros-ec-hwmon.c | 244 ++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 253 insertions(+)
 create mode 100644 drivers/hwmon/cros-ec-hwmon.c

diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index 0649d53f3..3b9155f 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -1254,6 +1254,14 @@ config SENSORS_PCF8591
 	  These devices are hard to detect and rarely found on mainstream
 	  hardware.  If unsure, say N.
 
+config SENSORS_CROS_EC
+	tristate "ChromeOS EC hwmon"
+	depends on MFD_CROS_EC
+	help
+	  If you say yes here you get hwmon support that will expose the
+	  ChromeOS internal sensors for fanspeed and temperature to the
+	  Linux hwmon subsystem.
+
 source drivers/hwmon/pmbus/Kconfig
 
 config SENSORS_PWM_FAN
diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
index 5509edf..e59b5da 100644
--- a/drivers/hwmon/Makefile
+++ b/drivers/hwmon/Makefile
@@ -134,6 +134,7 @@ obj-$(CONFIG_SENSORS_PC87360)	+= pc87360.o
 obj-$(CONFIG_SENSORS_PC87427)	+= pc87427.o
 obj-$(CONFIG_SENSORS_PCF8591)	+= pcf8591.o
 obj-$(CONFIG_SENSORS_POWR1220)  += powr1220.o
+obj-$(CONFIG_SENSORS_CROS_EC)   += cros-ec-hwmon.o
 obj-$(CONFIG_SENSORS_PWM_FAN)	+= pwm-fan.o
 obj-$(CONFIG_SENSORS_S3C)	+= s3c-hwmon.o
 obj-$(CONFIG_SENSORS_SCH56XX_COMMON)+= sch56xx-common.o
diff --git a/drivers/hwmon/cros-ec-hwmon.c b/drivers/hwmon/cros-ec-hwmon.c
new file mode 100644
index 0000000..29d8b06
--- /dev/null
+++ b/drivers/hwmon/cros-ec-hwmon.c
@@ -0,0 +1,244 @@
+/*
+ * Copyright (c) 2017, National Instruments Corp.
+ *
+ * Chromium EC Fan speed and temperature sensor driver
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/device.h>
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/sysfs.h>
+#include <linux/spi/spi.h>
+#include <linux/module.h>
+#include <linux/err.h>
+#include <linux/of_platform.h>
+#include <linux/hwmon.h>
+#include <linux/hwmon-sysfs.h>
+#include <linux/bitops.h>
+#include <linux/mfd/cros_ec.h>
+
+struct cros_ec_hwmon_priv {
+	struct cros_ec_device *ec;
+	struct device *hwmon_dev;
+
+	struct attribute **attrs;
+
+	struct attribute_group attr_group;
+	const struct attribute_group *groups[2];
+};
+
+#define KELVIN_TO_MILLICELSIUS(x) (((x) - 273) * 1000)
+
+static int __cros_ec_hwmon_probe_fans(struct cros_ec_hwmon_priv *priv)
+{
+	int err, idx;
+	uint16_t data;
+
+	for (idx = 0; idx < EC_FAN_SPEED_ENTRIES; idx++) {
+		err = cros_ec_read_mapped_mem16(priv->ec,
+					       EC_MEMMAP_FAN + 2 * idx,
+					       &data);
+		if (err)
+			return err;
+
+		if (data == EC_FAN_SPEED_NOT_PRESENT)
+			break;
+	}
+
+	return idx;
+}
+
+static int __cros_ec_hwmon_probe_temps(struct cros_ec_hwmon_priv *priv)
+{
+	uint8_t data;
+	int err, idx;
+
+	err = cros_ec_read_mapped_mem8(priv->ec, EC_MEMMAP_THERMAL_VERSION,
+				       &data);
+
+	/* if we have a read error, or EC_MEMMAP_THERMAL_VERSION is not set,
+	 * most likely we don't have temperature sensors ...
+	 */
+	if (err || !data)
+		return 0;
+
+	for (idx = 0; idx < EC_TEMP_SENSOR_ENTRIES; idx++) {
+		err = cros_ec_read_mapped_mem8(priv->ec,
+					       EC_MEMMAP_TEMP_SENSOR + idx,
+					       &data);
+		if (err)
+			return idx;
+
+		/* this assumes that they're all good up to idx */
+		switch (data) {
+		case EC_TEMP_SENSOR_NOT_PRESENT:
+		case EC_TEMP_SENSOR_ERROR:
+		case EC_TEMP_SENSOR_NOT_POWERED:
+		case EC_TEMP_SENSOR_NOT_CALIBRATED:
+			return idx;
+		default:
+			continue;
+		};
+	}
+
+	return idx;
+}
+
+static ssize_t cros_ec_hwmon_read_fan_rpm(struct device *dev,
+				  struct device_attribute *attr,
+				  char *buf)
+{
+	uint16_t data;
+	int err;
+	struct sensor_device_attribute *sattr = to_sensor_dev_attr(attr);
+	struct cros_ec_hwmon_priv *priv = dev_get_drvdata(dev);
+
+	err = cros_ec_read_mapped_mem16(priv->ec,
+					EC_MEMMAP_FAN + 2 * sattr->index,
+					&data);
+	if (err)
+		return err;
+
+	return sprintf(buf, "%d\n", data);
+}
+
+static ssize_t cros_ec_hwmon_read_temp(struct device *dev,
+				  struct device_attribute *attr,
+				  char *buf)
+{
+	uint8_t data;
+	int err, tmp;
+
+	struct sensor_device_attribute *sattr = to_sensor_dev_attr(attr);
+	struct cros_ec_hwmon_priv *priv = dev_get_drvdata(dev);
+
+	err = cros_ec_read_mapped_mem8(priv->ec,
+				       EC_MEMMAP_TEMP_SENSOR + 1 * sattr->index,
+				       &data);
+	if (err)
+		return err;
+
+	switch (data) {
+	case EC_TEMP_SENSOR_NOT_PRESENT:
+	case EC_TEMP_SENSOR_ERROR:
+	case EC_TEMP_SENSOR_NOT_POWERED:
+	case EC_TEMP_SENSOR_NOT_CALIBRATED:
+		dev_info(priv->ec->dev, "Failure: result=%d\n", data);
+		return -EIO;
+	}
+
+	/* make sure we don't overflow when adding offset*/
+	tmp = data + EC_TEMP_SENSOR_OFFSET;
+
+	return sprintf(buf, "%d\n", KELVIN_TO_MILLICELSIUS(tmp));
+}
+
+static int cros_ec_hwmon_probe(struct platform_device *pdev)
+{
+	struct cros_ec_device *ec = dev_get_drvdata(pdev->dev.parent);
+	struct cros_ec_hwmon_priv *ec_hwmon;
+	struct sensor_device_attribute *attr;
+	int num_fans, num_temps, i;
+
+	ec_hwmon = devm_kzalloc(&pdev->dev, sizeof(*ec_hwmon), GFP_KERNEL);
+	if (!ec_hwmon)
+		return -ENOMEM;
+	ec_hwmon->ec = ec;
+
+	num_fans = __cros_ec_hwmon_probe_fans(ec_hwmon);
+	if (num_fans < 0)
+		return num_fans;
+
+	num_temps = __cros_ec_hwmon_probe_temps(ec_hwmon);
+	if (num_fans < 0)
+		return num_temps;
+
+	ec_hwmon->attrs = devm_kzalloc(&pdev->dev,
+				       sizeof(*ec_hwmon->attrs) *
+				       (num_fans + num_temps + 1),
+				       GFP_KERNEL);
+	if (!ec_hwmon->attrs)
+		return -ENOMEM;
+
+	for (i = 0; i < num_fans; i++) {
+		attr = devm_kzalloc(&pdev->dev, sizeof(*attr), GFP_KERNEL);
+		if (!attr)
+			return -ENOMEM;
+		sysfs_attr_init(&attr->dev_attr.attr);
+		attr->dev_attr.attr.name = devm_kasprintf(&pdev->dev,
+							  GFP_KERNEL,
+							  "fan%d_input",
+							  i);
+		if (!attr->dev_attr.attr.name)
+			return -ENOMEM;
+
+		attr->dev_attr.show = cros_ec_hwmon_read_fan_rpm;
+		attr->dev_attr.attr.mode = S_IRUGO;
+		attr->index = i;
+		ec_hwmon->attrs[i] = &attr->dev_attr.attr;
+
+	}
+
+	for (i = 0; i < num_temps; i++) {
+		attr = devm_kzalloc(&pdev->dev, sizeof(*attr), GFP_KERNEL);
+		if (!attr)
+			return -ENOMEM;
+		sysfs_attr_init(&attr->dev_attr.attr);
+		attr->dev_attr.attr.name = devm_kasprintf(&pdev->dev,
+							  GFP_KERNEL,
+							  "temp%d_input",
+							  i);
+		if (!attr->dev_attr.attr.name)
+			return -ENOMEM;
+
+		attr->dev_attr.show = cros_ec_hwmon_read_temp;
+		attr->dev_attr.attr.mode = S_IRUGO;
+		attr->index = i;
+		ec_hwmon->attrs[i + num_fans] = &attr->dev_attr.attr;
+
+	}
+
+	ec_hwmon->attr_group.attrs = ec_hwmon->attrs;
+	ec_hwmon->groups[0] = &ec_hwmon->attr_group;
+
+	ec_hwmon->hwmon_dev = devm_hwmon_device_register_with_groups(&pdev->dev,
+		    "ec_hwmon", ec_hwmon, ec_hwmon->groups);
+
+	if (IS_ERR(ec_hwmon->hwmon_dev))
+		return PTR_ERR(ec_hwmon->hwmon_dev);
+
+	platform_set_drvdata(pdev, ec_hwmon);
+
+	return 0;
+}
+
+#ifdef CONFIG_OF
+static const struct of_device_id cros_ec_hwmon_of_match[] = {
+	{ .compatible = "google,cros-ec-hwmon" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, cros_ec_hwmon_of_match);
+#endif
+
+static struct platform_driver cros_ec_hwmon_driver = {
+	.probe = cros_ec_hwmon_probe,
+	.driver = {
+		.name = "cros-ec-hwmon",
+		.of_match_table = of_match_ptr(cros_ec_hwmon_of_match),
+	},
+};
+module_platform_driver(cros_ec_hwmon_driver);
+
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("ChromeOS EC Hardware Monitor driver");
+MODULE_ALIAS("platform:cros-ec-hwmon");
+MODULE_AUTHOR("Moritz Fischer <mdf@kernel.org>");
-- 
2.7.4