powerpc/powernv: Infrastructure to read opal messages in generic format.

Opal now has a new messaging infrastructure to push the messages to
linux in a generic format for different type of messages using only one
event bit. The format of the opal message is as below:

struct opal_msg {
        uint32_t msg_type;
	uint32_t reserved;
	uint64_t params[8];
};

This patch allows clients to subscribe for notification for specific
message type. It is upto the subscriber to decipher the messages who showed
interested in receiving specific message type.

The interface to subscribe for notification is:

	int opal_message_notifier_register(enum OpalMessageType msg_type,
                                        struct notifier_block *nb)

The notifier will fetch the opal message when available and notify the
subscriber with message type and the opal message. It is subscribers
responsibility to copy the message data before returning from notifier
callback.
Signed-off-by: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/include/asm/opal.h

@@ -132,6 +132,8 @@ extern int opal_enter_rtas(struct rtas_args *args,
 #define OPAL_FLASH_VALIDATE			76
 #define OPAL_FLASH_MANAGE			77
 #define OPAL_FLASH_UPDATE			78
+#define OPAL_GET_MSG				85
+#define OPAL_CHECK_ASYNC_COMPLETION		86
 
 #ifndef __ASSEMBLY__
 
@@ -211,7 +213,16 @@ enum OpalPendingState {
 	OPAL_EVENT_ERROR_LOG		= 0x40,
 	OPAL_EVENT_EPOW			= 0x80,
 	OPAL_EVENT_LED_STATUS		= 0x100,
-	OPAL_EVENT_PCI_ERROR		= 0x200
+	OPAL_EVENT_PCI_ERROR		= 0x200,
+	OPAL_EVENT_MSG_PENDING		= 0x800,
+};
+
+enum OpalMessageType {
+	OPAL_MSG_ASYNC_COMP		= 0,
+	OPAL_MSG_MEM_ERR,
+	OPAL_MSG_EPOW,
+	OPAL_MSG_SHUTDOWN,
+	OPAL_MSG_TYPE_MAX,
 };
 
 /* Machine check related definitions */
@@ -356,6 +367,12 @@ enum OpalLPCAddressType {
 	OPAL_LPC_FW	= 2,
 };
 
+struct opal_msg {
+	uint32_t msg_type;
+	uint32_t reserved;
+	uint64_t params[8];
+};
+
 struct opal_machine_check_event {
 	enum OpalMCE_Version	version:8;	/* 0x00 */
 	uint8_t			in_use;		/* 0x01 */
@@ -731,6 +748,9 @@ int64_t opal_validate_flash(uint64_t buffer, uint32_t *size, uint32_t *result);
 int64_t opal_manage_flash(uint8_t op);
 int64_t opal_update_flash(uint64_t blk_list);
 
+int64_t opal_get_msg(uint64_t buffer, size_t size);
+int64_t opal_check_completion(uint64_t buffer, size_t size, uint64_t token);
+
 /* Internal functions */
 extern int early_init_dt_scan_opal(unsigned long node, const char *uname, int depth, void *data);
 
@@ -744,6 +764,8 @@ extern int early_init_dt_scan_opal(unsigned long node, const char *uname,
 				   int depth, void *data);
 
 extern int opal_notifier_register(struct notifier_block *nb);
+extern int opal_message_notifier_register(enum OpalMessageType msg_type,
+						struct notifier_block *nb);
 extern void opal_notifier_enable(void);
 extern void opal_notifier_disable(void);
 extern void opal_notifier_update_evt(uint64_t evt_mask, uint64_t evt_val);

arch/powerpc/platforms/powernv/opal-wrappers.S

@@ -126,3 +126,5 @@ OPAL_CALL(opal_return_cpu,			OPAL_RETURN_CPU);
 OPAL_CALL(opal_validate_flash,			OPAL_FLASH_VALIDATE);
 OPAL_CALL(opal_manage_flash,			OPAL_FLASH_MANAGE);
 OPAL_CALL(opal_update_flash,			OPAL_FLASH_UPDATE);
+OPAL_CALL(opal_get_msg,				OPAL_GET_MSG);
+OPAL_CALL(opal_check_completion,		OPAL_CHECK_ASYNC_COMPLETION);

arch/powerpc/platforms/powernv/opal.c

@@ -40,6 +40,7 @@ extern u64 opal_mc_secondary_handler[];
 static unsigned int *opal_irqs;
 static unsigned int opal_irq_count;
 static ATOMIC_NOTIFIER_HEAD(opal_notifier_head);
+static struct atomic_notifier_head opal_msg_notifier_head[OPAL_MSG_TYPE_MAX];
 static DEFINE_SPINLOCK(opal_notifier_lock);
 static uint64_t last_notified_mask = 0x0ul;
 static atomic_t opal_notifier_hold = ATOMIC_INIT(0);
@@ -167,6 +168,95 @@ void opal_notifier_disable(void)
 	atomic_set(&opal_notifier_hold, 1);
 }
 
+/*
+ * Opal message notifier based on message type. Allow subscribers to get
+ * notified for specific messgae type.
+ */
+int opal_message_notifier_register(enum OpalMessageType msg_type,
+					struct notifier_block *nb)
+{
+	if (!nb) {
+		pr_warning("%s: Invalid argument (%p)\n",
+			   __func__, nb);
+		return -EINVAL;
+	}
+	if (msg_type > OPAL_MSG_TYPE_MAX) {
+		pr_warning("%s: Invalid message type argument (%d)\n",
+			   __func__, msg_type);
+		return -EINVAL;
+	}
+	return atomic_notifier_chain_register(
+				&opal_msg_notifier_head[msg_type], nb);
+}
+
+static void opal_message_do_notify(uint32_t msg_type, void *msg)
+{
+	/* notify subscribers */
+	atomic_notifier_call_chain(&opal_msg_notifier_head[msg_type],
+					msg_type, msg);
+}
+
+static void opal_handle_message(void)
+{
+	s64 ret;
+	/*
+	 * TODO: pre-allocate a message buffer depending on opal-msg-size
+	 * value in /proc/device-tree.
+	 */
+	static struct opal_msg msg;
+
+	ret = opal_get_msg(__pa(&msg), sizeof(msg));
+	/* No opal message pending. */
+	if (ret == OPAL_RESOURCE)
+		return;
+
+	/* check for errors. */
+	if (ret) {
+		pr_warning("%s: Failed to retrive opal message, err=%lld\n",
+				__func__, ret);
+		return;
+	}
+
+	/* Sanity check */
+	if (msg.msg_type > OPAL_MSG_TYPE_MAX) {
+		pr_warning("%s: Unknown message type: %u\n",
+				__func__, msg.msg_type);
+		return;
+	}
+	opal_message_do_notify(msg.msg_type, (void *)&msg);
+}
+
+static int opal_message_notify(struct notifier_block *nb,
+			  unsigned long events, void *change)
+{
+	if (events & OPAL_EVENT_MSG_PENDING)
+		opal_handle_message();
+	return 0;
+}
+
+static struct notifier_block opal_message_nb = {
+	.notifier_call	= opal_message_notify,
+	.next		= NULL,
+	.priority	= 0,
+};
+
+static int __init opal_message_init(void)
+{
+	int ret, i;
+
+	for (i = 0; i < OPAL_MSG_TYPE_MAX; i++)
+		ATOMIC_INIT_NOTIFIER_HEAD(&opal_msg_notifier_head[i]);
+
+	ret = opal_notifier_register(&opal_message_nb);
+	if (ret) {
+		pr_err("%s: Can't register OPAL event notifier (%d)\n",
+		       __func__, ret);
+		return ret;
+	}
+	return 0;
+}
+early_initcall(opal_message_init);
+
 int opal_get_chars(uint32_t vtermno, char *buf, int count)
 {
 	s64 rc;