qed: Revise MFW command locking

Interaction of driver -> management firmware is based
on a one-pending mailbox [per interface], and various
mailbox commands need to be synchronized.

Current scheme is messy, and there's a difficulty extending
it as it deals differently with various commands as well as
making assumption on the required behavior for load/unload
requests.

Drop the current scheme into a completion-list-based approach;
Each flow would try sending the command when possible,
allowing one flow to complete another flow's completion and
relieve the mailbox before sending its own command.
Signed-off-by: Tomer Tayar <Tomer.Tayar@cavium.com>
Signed-off-by: Yuval Mintz <Yuval.Mintz@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/qlogic/qed/qed_mcp.h

@@ -484,8 +484,13 @@ int qed_mcp_bist_nvm_test_get_image_att(struct qed_hwfn *p_hwfn,
 				  qed_device_num_engines((_p_hwfn)->cdev)))
 
 struct qed_mcp_info {
-	/* Spinlock used for protecting the access to the MFW mailbox */
-	spinlock_t				lock;
+	/* List for mailbox commands which were sent and wait for a response */
+	struct list_head			cmd_list;
+
+	/* Spinlock used for protecting the access to the mailbox commands list
+	 * and the sending of the commands.
+	 */
+	spinlock_t				cmd_lock;
 
 	/* Spinlock used for syncing SW link-changes and link-changes
 	 * originating from attention context.
@@ -505,7 +510,7 @@ struct qed_mcp_info {
 	u8					*mfw_mb_cur;
 	u8					*mfw_mb_shadow;
 	u16					mfw_mb_length;
-	u16					mcp_hist;
+	u32					mcp_hist;
 };
 
 struct qed_mcp_mb_params {