[RFC 1/2] powerpc/powernv: Get a unique token for async completions

[Shilpasri G Bhat]

This patch adds support to get a unique token for async completion
requests. This will be used for creating non-repititive request
handles for consecutive requests in OPAL-OCC command/response
interface.

Signed-off-by: Shilpasri G Bhat <shilpa.bhat at linux.vnet.ibm.com>
---
 arch/powerpc/include/asm/opal.h             |  1 +
 arch/powerpc/platforms/powernv/opal-async.c | 46 +++++++++++++++++++++++++++++
 2 files changed, 47 insertions(+)

diff --git a/arch/powerpc/include/asm/opal.h b/arch/powerpc/include/asm/opal.h
index 588fb1c..03ed493 100644
--- a/arch/powerpc/include/asm/opal.h
+++ b/arch/powerpc/include/asm/opal.h
@@ -293,6 +293,7 @@ extern int opal_message_notifier_unregister(enum opal_msg_type msg_type,
 
 extern int __opal_async_get_token(void);
 extern int opal_async_get_token_interruptible(void);
+extern int opal_async_get_unique_token_interruptible(int last_token);
 extern int __opal_async_release_token(int token);
 extern int opal_async_release_token(int token);
 extern int opal_async_wait_response(uint64_t token, struct opal_msg *msg);
diff --git a/arch/powerpc/platforms/powernv/opal-async.c b/arch/powerpc/platforms/powernv/opal-async.c
index 83bebee..8caeea2 100644
--- a/arch/powerpc/platforms/powernv/opal-async.c
+++ b/arch/powerpc/platforms/powernv/opal-async.c
@@ -73,6 +73,52 @@ int opal_async_get_token_interruptible(void)
 }
 EXPORT_SYMBOL_GPL(opal_async_get_token_interruptible);
 
+static int __opal_async_get_new_token(int last_token)
+{
+	unsigned long flags;
+	int token;
+
+	spin_lock_irqsave(&opal_async_comp_lock, flags);
+	token = find_next_bit(opal_async_complete_map, opal_max_async_tokens,
+			      last_token + 1);
+	if (token >= opal_max_async_tokens) {
+		token = find_first_bit(opal_async_complete_map,
+				       opal_max_async_tokens);
+		if (token >= opal_max_async_tokens || token == last_token) {
+			token = -EBUSY;
+			goto out;
+		}
+	}
+
+	pr_debug("%s token = %d\n", __func__, token);
+	if (__test_and_set_bit(token, opal_async_token_map)) {
+		token = -EBUSY;
+		goto out;
+	}
+
+	__clear_bit(token, opal_async_complete_map);
+
+out:
+	spin_unlock_irqrestore(&opal_async_comp_lock, flags);
+	return token;
+}
+
+int opal_async_get_unique_token_interruptible(int last_token)
+{
+	int token;
+
+	/* Wait until a token is available */
+	if (down_interruptible(&opal_async_sem))
+		return -ERESTARTSYS;
+
+	token = __opal_async_get_new_token(last_token);
+	if (token < 0)
+		up(&opal_async_sem);
+
+	return token;
+}
+EXPORT_SYMBOL_GPL(opal_async_get_unique_token_interruptible);
+
 int __opal_async_release_token(int token)
 {
 	unsigned long flags;
-- 
1.8.3.1