SCPI: Add function to query CSS power state

This patch adds the function scpi_get_css_power_state to perform the
'Get CSS Power State' SCP command and handle its response. The function
parses SCP response to obtain power states of requested cluster and CPUs
within.

Change-Id: I3ea26e48dff1a139da73f6c1e0893f21accaf9f0

plat/arm/css/common/css_scpi.c

@@ -41,11 +41,18 @@
 #define SCPI_SHARED_MEM_AP_TO_SCP	(PLAT_CSS_SCP_COM_SHARED_MEM_BASE \
 								 + 0x100)
 
+/* Header and payload addresses for commands from AP to SCP */
 #define SCPI_CMD_HEADER_AP_TO_SCP		\
 	((scpi_cmd_t *) SCPI_SHARED_MEM_AP_TO_SCP)
 #define SCPI_CMD_PAYLOAD_AP_TO_SCP		\
 	((void *) (SCPI_SHARED_MEM_AP_TO_SCP + sizeof(scpi_cmd_t)))
 
+/* Header and payload addresses for responses from SCP to AP */
+#define SCPI_RES_HEADER_SCP_TO_AP \
+	((scpi_cmd_t *) SCPI_SHARED_MEM_SCP_TO_AP)
+#define SCPI_RES_PAYLOAD_SCP_TO_AP \
+	((void *) (SCPI_SHARED_MEM_SCP_TO_AP + sizeof(scpi_cmd_t)))
+
 /* ID of the MHU slot used for the SCPI protocol */
 #define SCPI_MHU_SLOT_ID		0
 
@@ -163,6 +170,68 @@ void scpi_set_css_power_state(unsigned mpidr, scpi_power_state_t cpu_state,
 	scpi_secure_message_end();
 }
 
+/*
+ * Query and obtain CSS power state from SCP.
+ *
+ * In response to the query, SCP returns power states of all CPUs in all
+ * clusters of the system. The returned response is then filtered based on the
+ * supplied MPIDR. Power states of requested cluster and CPUs within are updated
+ * via. supplied non-NULL pointer arguments.
+ *
+ * Returns 0 on success, or -1 on errors.
+ */
+int scpi_get_css_power_state(unsigned int mpidr, unsigned int *cpu_state_p,
+		unsigned int *cluster_state_p)
+{
+	scpi_cmd_t *cmd;
+	scpi_cmd_t response;
+	int power_state, cpu, cluster, rc = -1;
+
+	/*
+	 * Extract CPU and cluster membership of the given MPIDR. SCPI caters
+	 * for only up to 0xf clusters, and 8 CPUs per cluster
+	 */
+	cpu = mpidr & MPIDR_AFFLVL_MASK;
+	cluster = (mpidr >> MPIDR_AFF1_SHIFT) & MPIDR_AFFLVL_MASK;
+	if (cpu >= 8 || cluster >= 0xf)
+		return -1;
+
+	scpi_secure_message_start();
+
+	/* Populate request headers */
+	cmd = memset(SCPI_CMD_HEADER_AP_TO_SCP, 0, sizeof(*cmd));
+	cmd->id = SCPI_CMD_GET_CSS_POWER_STATE;
+
+	/*
+	 * Send message and wait for SCP's response
+	 */
+	scpi_secure_message_send(0);
+	scpi_secure_message_receive(&response);
+
+	if (response.status != SCP_OK)
+		goto exit;
+
+	/* Validate SCP response */
+	if (!CHECK_RESPONSE(response, cluster))
+		goto exit;
+
+	/* Extract power states for required cluster */
+	power_state = *(((uint16_t *) SCPI_RES_PAYLOAD_SCP_TO_AP) + cluster);
+	if (CLUSTER_ID(power_state) != cluster)
+		goto exit;
+
+	/* Update power state via. pointers */
+	if (cluster_state_p)
+		*cluster_state_p = CLUSTER_POWER_STATE(power_state);
+	if (cpu_state_p)
+		*cpu_state_p = CPU_POWER_STATE(power_state);
+	rc = 0;
+
+exit:
+	scpi_secure_message_end();
+	return rc;
+}
+
 uint32_t scpi_sys_power_state(scpi_system_state_t system_state)
 {
 	scpi_cmd_t *cmd;

plat/arm/css/common/css_scpi.h

 /*
- * Copyright (c) 2014-2015, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2014-2016, ARM Limited and Contributors. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
@@ -81,9 +81,34 @@ typedef uint32_t scpi_status_t;
 typedef enum {
 	SCPI_CMD_SCP_READY = 0x01,
 	SCPI_CMD_SET_CSS_POWER_STATE = 0x03,
+	SCPI_CMD_GET_CSS_POWER_STATE = 0x04,
 	SCPI_CMD_SYS_POWER_STATE = 0x05
 } scpi_command_t;
 
+/*
+ * Macros to parse SCP response to GET_CSS_POWER_STATE command
+ *
+ *   [3:0] : cluster ID
+ *   [7:4] : cluster state: 0 = on; 3 = off; rest are reserved
+ *   [15:8]: on/off state for individual CPUs in the cluster
+ *
+ * Payload is in little-endian
+ */
+#define CLUSTER_ID(_resp)		((_resp) & 0xf)
+#define CLUSTER_POWER_STATE(_resp)	(((_resp) >> 4) & 0xf)
+
+/* Result is a bit mask of CPU on/off states in the cluster */
+#define CPU_POWER_STATE(_resp)		(((_resp) >> 8) & 0xff)
+
+/*
+ * For GET_CSS_POWER_STATE, SCP returns the power states of every cluster. The
+ * size of response depends on the number of clusters in the system. The
+ * SCP-to-AP payload contains 2 bytes per cluster. Make sure the response is
+ * large enough to contain power states of a given cluster
+ */
+#define CHECK_RESPONSE(_resp, _clus) \
+	(_resp.size >= (((_clus) + 1) * 2))
+
 typedef enum {
 	scpi_power_on = 0,
 	scpi_power_retention = 1,
@@ -101,6 +126,8 @@ extern void scpi_set_css_power_state(unsigned mpidr,
 					scpi_power_state_t cpu_state,
 					scpi_power_state_t cluster_state,
 					scpi_power_state_t css_state);
+int scpi_get_css_power_state(unsigned int mpidr, unsigned int *cpu_state_p,
+		unsigned int *cluster_state_p);
 uint32_t scpi_sys_power_state(scpi_system_state_t system_state);