From 82101a443a8696240cba3e59830470bab553bb1b Mon Sep 17 00:00:00 2001
From: Hans Petter Selasky <hselasky@FreeBSD.org>
Date: Tue, 2 Oct 2018 16:01:33 +0000
Subject: [PATCH] Selectivly backport fix for firmware command hang when
 switching from polling-based firmware commands to event based firmware
 commands.

This is a direct commit.

Linux commit:
a7e1f04905e5b2b90251974dddde781301b6be37

Sponsored by:	Mellanox Technologies
---
 sys/ofed/drivers/net/mlx4/cmd.c  | 22 ++++++++++++++++------
 sys/ofed/drivers/net/mlx4/mlx4.h |  2 ++
 2 files changed, 18 insertions(+), 6 deletions(-)

diff --git a/sys/ofed/drivers/net/mlx4/cmd.c b/sys/ofed/drivers/net/mlx4/cmd.c
index f0805e8c8afa..88137a5a430b 100644
--- a/sys/ofed/drivers/net/mlx4/cmd.c
+++ b/sys/ofed/drivers/net/mlx4/cmd.c
@@ -794,14 +794,19 @@ int __mlx4_cmd(struct mlx4_dev *dev, u64 in_param, u64 *out_param,
 		return -EIO;
 
 	if (!mlx4_is_mfunc(dev) || (native && mlx4_is_master(dev))) {
+		int ret;
+
+		down_read(&mlx4_priv(dev)->cmd.switch_sem);
 		if (mlx4_priv(dev)->cmd.use_events)
-			return mlx4_cmd_wait(dev, in_param, out_param,
-					     out_is_imm, in_modifier,
-					     op_modifier, op, timeout);
+			ret = mlx4_cmd_wait(dev, in_param, out_param,
+					    out_is_imm, in_modifier,
+					    op_modifier, op, timeout);
 		else
-			return mlx4_cmd_poll(dev, in_param, out_param,
-					     out_is_imm, in_modifier,
-					     op_modifier, op, timeout);
+			ret = mlx4_cmd_poll(dev, in_param, out_param,
+					    out_is_imm, in_modifier,
+					    op_modifier, op, timeout);
+		up_read(&mlx4_priv(dev)->cmd.switch_sem);
+		return ret;
 	}
 	return mlx4_slave_cmd(dev, in_param, out_param, out_is_imm,
 			      in_modifier, op_modifier, op, timeout);
@@ -2253,6 +2258,7 @@ int mlx4_cmd_init(struct mlx4_dev *dev)
 {
 	struct mlx4_priv *priv = mlx4_priv(dev);
 
+	init_rwsem(&priv->cmd.switch_sem);
 	mutex_init(&priv->cmd.hcr_mutex);
 	mutex_init(&priv->cmd.slave_cmd_mutex);
 	sema_init(&priv->cmd.poll_sem, 1);
@@ -2351,6 +2357,7 @@ int mlx4_cmd_use_events(struct mlx4_dev *dev)
 	if (!priv->cmd.context)
 		return -ENOMEM;
 
+	down_write(&priv->cmd.switch_sem);
 	for (i = 0; i < priv->cmd.max_cmds; ++i) {
 		priv->cmd.context[i].token = i;
 		priv->cmd.context[i].next  = i + 1;
@@ -2370,6 +2377,7 @@ int mlx4_cmd_use_events(struct mlx4_dev *dev)
 
 	down(&priv->cmd.poll_sem);
 	priv->cmd.use_events = 1;
+	up_write(&priv->cmd.switch_sem);
 
 	return err;
 }
@@ -2382,6 +2390,7 @@ void mlx4_cmd_use_polling(struct mlx4_dev *dev)
 	struct mlx4_priv *priv = mlx4_priv(dev);
 	int i;
 
+	down_write(&priv->cmd.switch_sem);
 	priv->cmd.use_events = 0;
 
 	for (i = 0; i < priv->cmd.max_cmds; ++i)
@@ -2390,6 +2399,7 @@ void mlx4_cmd_use_polling(struct mlx4_dev *dev)
 	kfree(priv->cmd.context);
 
 	up(&priv->cmd.poll_sem);
+	up_write(&priv->cmd.switch_sem);
 }
 
 struct mlx4_cmd_mailbox *mlx4_alloc_cmd_mailbox(struct mlx4_dev *dev)
diff --git a/sys/ofed/drivers/net/mlx4/mlx4.h b/sys/ofed/drivers/net/mlx4/mlx4.h
index bef2e004374e..8ebf64a4670d 100644
--- a/sys/ofed/drivers/net/mlx4/mlx4.h
+++ b/sys/ofed/drivers/net/mlx4/mlx4.h
@@ -44,6 +44,7 @@
 #include <linux/semaphore.h>
 #include <linux/workqueue.h>
 #include <linux/device.h>
+#include <linux/rwsem.h>
 #include <linux/mlx4/device.h>
 #include <linux/mlx4/driver.h>
 #include <linux/mlx4/doorbell.h>
@@ -596,6 +597,7 @@ struct mlx4_cmd {
 	struct mutex		slave_cmd_mutex;
 	struct semaphore	poll_sem;
 	struct semaphore	event_sem;
+	struct rw_semaphore	switch_sem;
 	int			max_cmds;
 	spinlock_t		context_lock;
 	int			free_head;