powerpc/powernv: Enhance opal message read interface

Use "opal-msg-size" device tree property to allocate memory for
"opal_msg".

Signed-off-by: Vasant Hegde <hegdevasant@linux.vnet.ibm.com>
[mpe: s/uint32_t/u32/ and mark opal_msg_size as __ro_after_init]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20190826065701.8853-1-hegdevasant@linux.vnet.ibm.com

arch/powerpc/platforms/powernv/opal.c

@@ -58,6 +58,8 @@ static DEFINE_SPINLOCK(opal_write_lock);
 static struct atomic_notifier_head opal_msg_notifier_head[OPAL_MSG_TYPE_MAX];
 static uint32_t opal_heartbeat;
 static struct task_struct *kopald_tsk;
+static struct opal_msg *opal_msg;
+static u32 opal_msg_size __ro_after_init;
 
 void opal_configure_cores(void)
 {
@@ -271,14 +273,9 @@ static void opal_message_do_notify(uint32_t msg_type, void *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;
 	u32 type;
 
-	ret = opal_get_msg(__pa(&msg), sizeof(msg));
+	ret = opal_get_msg(__pa(opal_msg), opal_msg_size);
 	/* No opal message pending. */
 	if (ret == OPAL_RESOURCE)
 		return;
@@ -290,14 +287,14 @@ static void opal_handle_message(void)
 		return;
 	}
 
-	type = be32_to_cpu(msg.msg_type);
+	type = be32_to_cpu(opal_msg->msg_type);
 
 	/* Sanity check */
 	if (type >= OPAL_MSG_TYPE_MAX) {
 		pr_warn_once("%s: Unknown message type: %u\n", __func__, type);
 		return;
 	}
-	opal_message_do_notify(type, (void *)&msg);
+	opal_message_do_notify(type, (void *)opal_msg);
 }
 
 static irqreturn_t opal_message_notify(int irq, void *data)
@@ -306,10 +303,24 @@ static irqreturn_t opal_message_notify(int irq, void *data)
 	return IRQ_HANDLED;
 }
 
-static int __init opal_message_init(void)
+static int __init opal_message_init(struct device_node *opal_node)
 {
 	int ret, i, irq;
 
+	ret = of_property_read_u32(opal_node, "opal-msg-size", &opal_msg_size);
+	if (ret) {
+		pr_notice("Failed to read opal-msg-size property\n");
+		opal_msg_size = sizeof(struct opal_msg);
+	}
+
+	opal_msg = kmalloc(opal_msg_size, GFP_KERNEL);
+	if (!opal_msg) {
+		opal_msg_size = sizeof(struct opal_msg);
+		/* Try to allocate fixed message size */
+		opal_msg = kmalloc(opal_msg_size, GFP_KERNEL);
+		BUG_ON(opal_msg == NULL);
+	}
+
 	for (i = 0; i < OPAL_MSG_TYPE_MAX; i++)
 		ATOMIC_INIT_NOTIFIER_HEAD(&opal_msg_notifier_head[i]);
 
@@ -913,7 +924,7 @@ static int __init opal_init(void)
 	}
 
 	/* Initialise OPAL messaging system */
-	opal_message_init();
+	opal_message_init(opal_node);
 
 	/* Initialise OPAL asynchronous completion interface */
 	opal_async_comp_init();