arm64: Implement PSCI command support

Provide support for SoCs to participate in PSCI commands.
There are 2 steps to a command:
1. prepare() - look at request and adjust state accordingly
2. commit() - take action on the command

The prepare() function is called with psci locks held while
the commit() function is called with the locks dropped.
No SoC implements the appropriate logic yet.

BUG=chrome-os-partner:32136
BRANCH=None
TEST=Booted PSCI kernel -- no SMP because cmd_prepare()
     knowingly fails. Spintable kernel still brings up both
     CPUs.

Change-Id: I2ae4d1c3f3eac4d1060c1b41472909933815d078
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Original-Commit-Id: 698d38b53bbc2bc043548792cea7219542b5fe6b
Original-Change-Id: I0821dc2ee8dc6bd1e8bc1c10f8b98b10e24fc97e
Original-Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/226485
Original-Reviewed-by: Furquan Shaikh <furquan@chromium.org>
Reviewed-on: http://review.coreboot.org/9423
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Tested-by: build bot (Jenkins)

src/arch/arm64/armv8/secmon/psci.c

@@ -174,15 +174,18 @@ static void psci_cpu_on_callback(void *arg)
 				e->cpu_state.startup.arg, &state);
 }
 
-static void psci_cpu_on_prepare(struct psci_node *e, const struct cpu_action *a)
+static void psci_cpu_on_prepare(struct psci_cmd *cmd,
+				const struct cpu_action *a)
 {
 	struct psci_node *ancestor;
+	struct psci_node *e;
 	int state = PSCI_STATE_ON_PENDING;
 
+	e = cmd->target;
 	e->cpu_state.startup = *a;
 	ancestor = psci_find_ancestor(e, PSCI_AFFINITY_LEVEL_HIGHEST, state);
 	e->cpu_state.ancestor = ancestor;
-	psci_set_hierarchy_state(e, ancestor, state);
+	cmd->ancestor = ancestor;
 }
 
 static int psci_schedule_cpu_on(struct psci_node *e)
@@ -206,6 +209,9 @@ static int psci_schedule_cpu_on(struct psci_node *e)
 void psci_turn_on_self(const struct cpu_action *action)
 {
 	struct psci_node *e = node_self();
+	struct psci_cmd cmd = {
+		.type = PSCI_CMD_ON,
+	};
 
 	if (e == NULL) {
 		printk(BIOS_ERR, "Couldn't turn on self: mpidr %llx\n",
@@ -213,8 +219,11 @@ void psci_turn_on_self(const struct cpu_action *action)
 		return;
 	}
 
+	cmd.target = e;
+
 	psci_lock();
-	psci_cpu_on_prepare(e, action);
+	psci_cpu_on_prepare(&cmd, action);
+	psci_set_hierarchy_state(e, cmd.ancestor, PSCI_STATE_ON_PENDING);
 	psci_unlock();
 
 	psci_schedule_cpu_on(e);
@@ -235,8 +244,12 @@ static void psci_cpu_on(struct psci_func *pf)
 	uint64_t target_mpidr;
 	uint64_t context_id;
 	int cpu_state;
+	int ret;
 	struct psci_node *e;
 	struct cpu_action action;
+	struct psci_cmd cmd = {
+		.type = PSCI_CMD_ON,
+	};
 
 	target_mpidr = psci64_arg(pf, PSCI_PARAM_0);
 	entry = psci64_arg(pf, PSCI_PARAM_1);
@@ -262,28 +275,71 @@ static void psci_cpu_on(struct psci_func *pf)
 		return;
 	}
 
+	cmd.target = e;
 	action.run = (void *)entry;
 	action.arg = (void *)context_id;
-	psci_cpu_on_prepare(e, &action);
+	psci_cpu_on_prepare(&cmd, &action);
+
+	ret = soc_psci_ops.cmd_prepare(&cmd);
+
+	if (ret == PSCI_RET_SUCCESS)
+		psci_set_hierarchy_state(e, cmd.ancestor,
+					PSCI_STATE_ON_PENDING);
+
 	psci_unlock();
 
+	if (ret != PSCI_RET_SUCCESS)
+		return psci32_return(pf, ret);
+
+	ret = soc_psci_ops.cmd_commit(&cmd);
+
+	if (ret != PSCI_RET_SUCCESS) {
+		psci_lock();
+		psci_set_hierarchy_state(e, cmd.ancestor, PSCI_STATE_OFF);
+		psci_unlock();
+		return psci32_return(pf, ret);
+	}
+
 	psci32_return(pf, psci_schedule_cpu_on(e));
 }
 
 static int psci_turn_off_node(struct psci_node *e, int level,
 					int state_id)
 {
-	struct psci_node *ancestor;
+	int ret;
+	struct psci_cmd cmd = {
+		.type = PSCI_CMD_OFF,
+		.state_id = state_id,
+		.target = e,
+	};
 
 	psci_lock();
-	ancestor = psci_find_ancestor(e, level, PSCI_STATE_OFF);
+
-	psci_set_hierarchy_state(e, ancestor, PSCI_STATE_OFF);
+	cmd.ancestor = psci_find_ancestor(e, level, PSCI_STATE_OFF);
+
+	ret = soc_psci_ops.cmd_prepare(&cmd);
+
+	if (ret == PSCI_RET_SUCCESS)
+		psci_set_hierarchy_state(e, cmd.ancestor, PSCI_STATE_OFF);
+
 	psci_unlock();
 
-	/* TODO(adurbin): writeback cache and actually turn off CPU. */
+	if (ret != PSCI_RET_SUCCESS)
-	secmon_trampoline(&secmon_wait_for_action, NULL);
+		return ret;
 
-	return PSCI_RET_SUCCESS;
+	/* Should never return. */
+	ret = soc_psci_ops.cmd_commit(&cmd);
+
+	/* Adjust ret to be an error. */
+	if (ret == PSCI_RET_SUCCESS)
+		ret = PSCI_RET_INTERNAL_FAILURE;
+
+	/* Turn things back on. */
+	psci_lock();
+	psci_set_hierarchy_state(e, cmd.ancestor, PSCI_STATE_ON);
+	psci_unlock();
+
+	return ret;
 }
 
 int psci_turn_off_self(void)

src/arch/arm64/include/arch/psci.h

@@ -104,12 +104,47 @@ static inline int psci_root_node(const struct psci_node *n)
 	return psci_node_parent(n) == NULL;
 }
 
+enum {
+	PSCI_CMD_ON,
+	PSCI_CMD_OFF,
+	PSCI_CMD_STANDBY,
+};
+
+/*
+ * PSCI actions are serialized into a command for the SoC to process. There are
+ * 2 phases of a command being processed: prepare and commit. The prepare() is
+ * called with the PSCI locks held for the state of the PSCI nodes. If
+ * successful, the appropriate locks will be dropped and commit() will be
+ * called with the same structure. It is permissible for the SoC support code
+ * to modify the struture passed in (e.g. to update the requested state_id to
+ * reflect dynamic constraints on how deep of a state to enter).
+ */
+struct psci_cmd {
+	/* Command type. */
+	int type;
+	/*
+	 * PSCI state id for PSCI_CMD_OFF and PSCI_CMD_STANDBY commands.
+	 * A value of -1 indicates a CPU_OFF request.
+	 */
+	int state_id;
+	/*
+	 * target is the command's target, but it can affect up to the
+	 * ancestor entity. If target == ancestor then it only affects
+	 * target, otherwise all entites up the hierarchy including ancestor.
+	 */
+	struct psci_node *target;
+	struct psci_node *ancestor;
+};
+
 struct psci_soc_ops {
 	/*
 	 * Return number of entities one level below given parent affinitly
 	 * level and mpidr.
 	 */
 	size_t (*children_at_level)(int parent_level, uint64_t mpidr);
+
+	int (*cmd_prepare)(struct psci_cmd *cmd);
+	int (*cmd_commit)(struct psci_cmd *cmd);
 };
 
 /* Each SoC needs to provide the functions in the psci_soc_ops structure. */

src/soc/nvidia/tegra132/psci.c

@@ -45,6 +45,18 @@ static size_t children_at_level(int parent_level, uint64_t mpidr)
 	}
 }
 
+static int cmd_prepare(struct psci_cmd *cmd)
+{
+	return PSCI_RET_NOT_SUPPORTED;
+}
+
+static int cmd_commit(struct psci_cmd *cmd)
+{
+	return PSCI_RET_NOT_SUPPORTED;
+}
+
 struct psci_soc_ops soc_psci_ops = {
 	.children_at_level = &children_at_level,
+	.cmd_prepare = &cmd_prepare,
+	.cmd_commit = &cmd_commit,
 };