greybus: svc: add Interface power measurements support

This change implements the AP Power Monitor functions for obtaining
current/voltage/power on a specific rail of an Interface.

Testing Done:

$ cat /sys/bus/greybus/devices/1-3/current_now
103
$ cat /sys/bus/greybus/devices/1-3/power_now
303
$ cat /sys/bus/greybus/devices/1-3/voltage_now
203
Signed-off-by: David Lin <dtwlin@google.com>
Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

drivers/staging/greybus/Documentation/sysfs-bus-greybus

@@ -164,3 +164,24 @@ Contact:	Greg Kroah-Hartman <greg@kroah.com>
 Description:
 		If the SVC watchdog is enabled or not.  Writing 0 to this
 		file will disable the watchdog, writing 1 will enable it.
+
+What:		/sys/bus/greybus/device/N-I/voltage_now
+Date:		March 2016
+KernelVersion:	4.XX
+Contact:	Greg Kroah-Hartman <greg@kroah.com>
+Description:
+		Voltage measurement of the interface in microvolts (uV)
+
+What:		/sys/bus/greybus/device/N-I/current_now
+Date:		March 2016
+KernelVersion:	4.XX
+Contact:	Greg Kroah-Hartman <greg@kroah.com>
+Description:
+		Current measurement of the interface in microamps (uA)
+
+What:		/sys/bus/greybus/device/N-I/power_now
+Date:		March 2016
+KernelVersion:	4.XX
+Contact:	Greg Kroah-Hartman <greg@kroah.com>
+Description:
+		Power measurement of the interface in microwatts (uW)

drivers/staging/greybus/greybus_protocols.h

@@ -798,6 +798,10 @@ struct gb_spi_transfer_response {
 #define GB_SVC_TYPE_INTF_EJECT			0x11
 #define GB_SVC_TYPE_KEY_EVENT			0x12
 #define GB_SVC_TYPE_PING			0x13
+#define GB_SVC_TYPE_PWRMON_RAIL_COUNT_GET	0x14
+#define GB_SVC_TYPE_PWRMON_RAIL_NAMES_GET	0x15
+#define GB_SVC_TYPE_PWRMON_SAMPLE_GET		0x16
+#define GB_SVC_TYPE_PWRMON_INTF_SAMPLE_GET	0x17
 
 /*
  * SVC version request/response has the same payload as
@@ -963,6 +967,25 @@ struct gb_svc_key_event_request {
 #define GB_SVC_KEY_PRESSED     0x01
 } __packed;
 
+#define GB_SVC_PWRMON_TYPE_CURR			0x01
+#define GB_SVC_PWRMON_TYPE_VOL			0x02
+#define GB_SVC_PWRMON_TYPE_PWR			0x03
+
+#define GB_SVC_PWRMON_GET_SAMPLE_OK		0x00
+#define GB_SVC_PWRMON_GET_SAMPLE_INVAL		0x01
+#define GB_SVC_PWRMON_GET_SAMPLE_NOSUPP		0x02
+#define GB_SVC_PWRMON_GET_SAMPLE_HWERR		0x03
+
+struct gb_svc_pwrmon_intf_sample_get_request {
+	__u8	intf_id;
+	__u8	measurement_type;
+} __packed;
+
+struct gb_svc_pwrmon_intf_sample_get_response {
+	__u8	result;
+	__le32	measurement;
+} __packed;
+
 /* RAW */
 
 /* Version of the Greybus raw protocol we support */

drivers/staging/greybus/interface.c

@@ -263,6 +263,63 @@ static ssize_t version_show(struct device *dev, struct device_attribute *attr,
 }
 static DEVICE_ATTR_RO(version);
 
+static ssize_t voltage_now_show(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	struct gb_interface *intf = to_gb_interface(dev);
+	int ret;
+	u32 measurement;
+
+	ret = gb_svc_pwrmon_intf_sample_get(intf->hd->svc, intf->interface_id,
+					    GB_SVC_PWRMON_TYPE_VOL,
+					    &measurement);
+	if (ret) {
+		dev_err(&intf->dev, "failed to get voltage sample (%d)\n", ret);
+		return ret;
+	}
+
+	return sprintf(buf, "%u\n", measurement);
+}
+static DEVICE_ATTR_RO(voltage_now);
+
+static ssize_t current_now_show(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	struct gb_interface *intf = to_gb_interface(dev);
+	int ret;
+	u32 measurement;
+
+	ret = gb_svc_pwrmon_intf_sample_get(intf->hd->svc, intf->interface_id,
+					    GB_SVC_PWRMON_TYPE_CURR,
+					    &measurement);
+	if (ret) {
+		dev_err(&intf->dev, "failed to get current sample (%d)\n", ret);
+		return ret;
+	}
+
+	return sprintf(buf, "%u\n", measurement);
+}
+static DEVICE_ATTR_RO(current_now);
+
+static ssize_t power_now_show(struct device *dev,
+			      struct device_attribute *attr, char *buf)
+{
+	struct gb_interface *intf = to_gb_interface(dev);
+	int ret;
+	u32 measurement;
+
+	ret = gb_svc_pwrmon_intf_sample_get(intf->hd->svc, intf->interface_id,
+					    GB_SVC_PWRMON_TYPE_PWR,
+					    &measurement);
+	if (ret) {
+		dev_err(&intf->dev, "failed to get power sample (%d)\n", ret);
+		return ret;
+	}
+
+	return sprintf(buf, "%u\n", measurement);
+}
+static DEVICE_ATTR_RO(power_now);
+
 static struct attribute *interface_attrs[] = {
 	&dev_attr_ddbl1_manufacturer_id.attr,
 	&dev_attr_ddbl1_product_id.attr,
@@ -273,6 +330,9 @@ static struct attribute *interface_attrs[] = {
 	&dev_attr_product_string.attr,
 	&dev_attr_serial_number.attr,
 	&dev_attr_version.attr,
+	&dev_attr_voltage_now.attr,
+	&dev_attr_current_now.attr,
+	&dev_attr_power_now.attr,
 	NULL,
 };
 ATTRIBUTE_GROUPS(interface);

drivers/staging/greybus/svc.c

@@ -99,6 +99,44 @@ static ssize_t watchdog_store(struct device *dev,
 }
 static DEVICE_ATTR_RW(watchdog);
 
+int gb_svc_pwrmon_intf_sample_get(struct gb_svc *svc, u8 intf_id,
+				  u8 measurement_type, u32 *value)
+{
+	struct gb_svc_pwrmon_intf_sample_get_request request;
+	struct gb_svc_pwrmon_intf_sample_get_response response;
+	int ret;
+
+	request.intf_id = intf_id;
+	request.measurement_type = measurement_type;
+
+	ret = gb_operation_sync(svc->connection,
+				GB_SVC_TYPE_PWRMON_INTF_SAMPLE_GET,
+				&request, sizeof(request),
+				&response, sizeof(response));
+	if (ret) {
+		dev_err(&svc->dev, "failed to get intf sample (%d)\n", ret);
+		return ret;
+	}
+
+	if (response.result) {
+		dev_err(&svc->dev,
+			"UniPro error while getting intf power sample (%d %d): %d\n",
+			intf_id, measurement_type, response.result);
+		switch (response.result) {
+		case GB_SVC_PWRMON_GET_SAMPLE_INVAL:
+			return -EINVAL;
+		case GB_SVC_PWRMON_GET_SAMPLE_NOSUPP:
+			return -ENOSYS;
+		default:
+			return -EIO;
+		}
+	}
+
+	*value = le32_to_cpu(response.measurement);
+
+	return 0;
+}
+
 static struct attribute *svc_attrs[] = {
 	&dev_attr_endo_id.attr,
 	&dev_attr_ap_intf_id.attr,

drivers/staging/greybus/svc.h

@@ -48,6 +48,8 @@ int gb_svc_add(struct gb_svc *svc);
 void gb_svc_del(struct gb_svc *svc);
 void gb_svc_put(struct gb_svc *svc);
 
+int gb_svc_pwrmon_intf_sample_get(struct gb_svc *svc, u8 intf_id,
+				  u8 measurement_type, u32 *value);
 int gb_svc_intf_device_id(struct gb_svc *svc, u8 intf_id, u8 device_id);
 int gb_svc_route_create(struct gb_svc *svc, u8 intf1_id, u8 dev1_id,
 			       u8 intf2_id, u8 dev2_id);