firmware: arm_scpi: add support for device power state management

SCPI protocol supports device power state management. This deals with
power states of various peripheral devices in the system other than the
core compute subsystem.

This patch adds support for the power state management of those
peripheral devices.

Tested-by: Mathieu Poirier <[e-mail]>
Tested-by: Jon Medhurst <[e-mail]>
Reviewed-by: Jon Medhurst <[e-mail]>
Reviewed-by: Kevin Hilman <[e-mail]>
Reviewed-by: Ulf Hansson <[e-mail]>
Signed-off-by: Sudeep Holla <[e-mail]>

drivers/firmware/arm_scpi.c

···
 	__le32 hi_val;
 } __packed;
 
+struct dev_pstate_set {
+	u16 dev_id;
+	u8 pstate;
+} __packed;
+
 static struct scpi_drvinfo *scpi_info;
 
 static int scpi_linux_errmap[SCPI_ERR_MAX] = {
···
 	return ret;
 }
 
+static int scpi_device_get_power_state(u16 dev_id)
+{
+	int ret;
+	u8 pstate;
+	__le16 id = cpu_to_le16(dev_id);
+
+	ret = scpi_send_message(SCPI_CMD_GET_DEVICE_PWR_STATE, &id,
+				sizeof(id), &pstate, sizeof(pstate));
+	return ret ? ret : pstate;
+}
+
+static int scpi_device_set_power_state(u16 dev_id, u8 pstate)
+{
+	int stat;
+	struct dev_pstate_set dev_set = {
+		.dev_id = cpu_to_le16(dev_id),
+		.pstate = pstate,
+	};
+
+	return scpi_send_message(SCPI_CMD_SET_DEVICE_PWR_STATE, &dev_set,
+				 sizeof(dev_set), &stat, sizeof(stat));
+}
+
 static struct scpi_ops scpi_ops = {
 	.get_version = scpi_get_version,
 	.clk_get_range = scpi_clk_get_range,
···
 	.sensor_get_capability = scpi_sensor_get_capability,
 	.sensor_get_info = scpi_sensor_get_info,
 	.sensor_get_value = scpi_sensor_get_value,
+	.device_get_power_state = scpi_device_get_power_state,
+	.device_set_power_state = scpi_device_set_power_state,
 };
 
 struct scpi_ops *get_scpi_ops(void)

include/linux/scpi_protocol.h

···
 	int (*sensor_get_capability)(u16 *sensors);
 	int (*sensor_get_info)(u16 sensor_id, struct scpi_sensor_info *);
 	int (*sensor_get_value)(u16, u64 *);
+	int (*device_get_power_state)(u16);
+	int (*device_set_power_state)(u16, u8);
 };
 
 #if IS_REACHABLE(CONFIG_ARM_SCPI_PROTOCOL)