qed: prevent a fw assert during device shutdown

Device firmware can assert if the device shutdown path in driver
encounters an async. events from mfw (processed in
qed_mcp_handle_events()) after qed_mcp_unload_req() returns.
A call to qed_mcp_unload_req() currently marks the device as inactive
and thus stops any new events, but there is a windows where in-flight
events might still be received by the driver.

To prevent this race condition, atomically set QED_MCP_BYPASS_PROC_BIT
in qed_mcp_unload_req() to make sure qed_mcp_handle_events() ignores all
events. Wait for any event that might already be in-process to complete
by monitoring QED_MCP_IN_PROCESSING_BIT.

Signed-off-by: Pravin Kumar Ganesh Dhende <pdhende@marvell.com>
Signed-off-by: Venkata Sudheer Kumar Bhavaraju <vbhavaraju@marvell.com>
Signed-off-by: Alok Prasad <palok@marvell.com>
Signed-off-by: Ariel Elior <aelior@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/qlogic/qed/qed_dev.c

@@ -3098,6 +3098,9 @@ int qed_hw_init(struct qed_dev *cdev, struct qed_hw_init_params *p_params)
 			continue;
 		}
 
+		/* Some flows may keep variable set */
+		p_hwfn->mcp_info->mcp_handling_status = 0;
+
 		rc = qed_calc_hw_mode(p_hwfn);
 		if (rc)
 			return rc;

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

@@ -140,7 +140,7 @@ static struct qed_mcp_cmd_elem *qed_mcp_cmd_get_elem(struct qed_hwfn *p_hwfn,
 int qed_mcp_free(struct qed_hwfn *p_hwfn)
 {
 	if (p_hwfn->mcp_info) {
-		struct qed_mcp_cmd_elem *p_cmd_elem, *p_tmp;
+		struct qed_mcp_cmd_elem *p_cmd_elem = NULL, *p_tmp;
 
 		kfree(p_hwfn->mcp_info->mfw_mb_cur);
 		kfree(p_hwfn->mcp_info->mfw_mb_shadow);
@@ -249,6 +249,7 @@ int qed_mcp_cmd_init(struct qed_hwfn *p_hwfn, struct qed_ptt *p_ptt)
 	/* Initialize the MFW spinlock */
 	spin_lock_init(&p_info->cmd_lock);
 	spin_lock_init(&p_info->link_lock);
+	spin_lock_init(&p_info->unload_lock);
 
 	INIT_LIST_HEAD(&p_info->cmd_list);
 
@@ -1095,10 +1096,15 @@ int qed_mcp_load_done(struct qed_hwfn *p_hwfn, struct qed_ptt *p_ptt)
 	return 0;
 }
 
+#define MFW_COMPLETION_MAX_ITER 5000
+#define MFW_COMPLETION_INTERVAL_MS 1
+
 int qed_mcp_unload_req(struct qed_hwfn *p_hwfn, struct qed_ptt *p_ptt)
 {
 	struct qed_mcp_mb_params mb_params;
+	u32 cnt = MFW_COMPLETION_MAX_ITER;
 	u32 wol_param;
+	int rc;
 
 	switch (p_hwfn->cdev->wol_config) {
 	case QED_OV_WOL_DISABLED:
@@ -1121,7 +1127,23 @@ int qed_mcp_unload_req(struct qed_hwfn *p_hwfn, struct qed_ptt *p_ptt)
 	mb_params.param = wol_param;
 	mb_params.flags = QED_MB_FLAG_CAN_SLEEP | QED_MB_FLAG_AVOID_BLOCK;
 
-	return qed_mcp_cmd_and_union(p_hwfn, p_ptt, &mb_params);
+	spin_lock_bh(&p_hwfn->mcp_info->unload_lock);
+	set_bit(QED_MCP_BYPASS_PROC_BIT,
+		&p_hwfn->mcp_info->mcp_handling_status);
+	spin_unlock_bh(&p_hwfn->mcp_info->unload_lock);
+
+	rc = qed_mcp_cmd_and_union(p_hwfn, p_ptt, &mb_params);
+
+	while (test_bit(QED_MCP_IN_PROCESSING_BIT,
+			&p_hwfn->mcp_info->mcp_handling_status) && --cnt)
+		msleep(MFW_COMPLETION_INTERVAL_MS);
+
+	if (!cnt)
+		DP_NOTICE(p_hwfn,
+			  "Failed to wait MFW event completion after %d msec\n",
+			  MFW_COMPLETION_MAX_ITER * MFW_COMPLETION_INTERVAL_MS);
+
+	return rc;
 }
 
 int qed_mcp_unload_done(struct qed_hwfn *p_hwfn, struct qed_ptt *p_ptt)
@@ -2021,6 +2043,19 @@ int qed_mcp_handle_events(struct qed_hwfn *p_hwfn,
 			   "Msg [%d] - old CMD 0x%02x, new CMD 0x%02x\n",
 			   i, info->mfw_mb_shadow[i], info->mfw_mb_cur[i]);
 
+		spin_lock_bh(&p_hwfn->mcp_info->unload_lock);
+		if (test_bit(QED_MCP_BYPASS_PROC_BIT,
+			     &p_hwfn->mcp_info->mcp_handling_status)) {
+			spin_unlock_bh(&p_hwfn->mcp_info->unload_lock);
+			DP_INFO(p_hwfn,
+				"Msg [%d] is bypassed on unload flow\n", i);
+			continue;
+		}
+
+		set_bit(QED_MCP_IN_PROCESSING_BIT,
+			&p_hwfn->mcp_info->mcp_handling_status);
+		spin_unlock_bh(&p_hwfn->mcp_info->unload_lock);
+
 		switch (i) {
 		case MFW_DRV_MSG_LINK_CHANGE:
 			qed_mcp_handle_link_change(p_hwfn, p_ptt, false);
@@ -2074,6 +2109,9 @@ int qed_mcp_handle_events(struct qed_hwfn *p_hwfn,
 			DP_INFO(p_hwfn, "Unimplemented MFW message %d\n", i);
 			rc = -EINVAL;
 		}
+
+		clear_bit(QED_MCP_IN_PROCESSING_BIT,
+			  &p_hwfn->mcp_info->mcp_handling_status);
 	}
 
 	/* ACK everything */

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

@@ -788,6 +788,14 @@ struct qed_mcp_info {
 
 	/* S/N for debug data mailbox commands */
 	atomic_t dbg_data_seq;
+
+	/* Spinlock used to sync the flag mcp_handling_status with
+	 * the mfw events handler
+	 */
+	spinlock_t unload_lock;
+	unsigned long mcp_handling_status;
+#define QED_MCP_BYPASS_PROC_BIT 0
+#define QED_MCP_IN_PROCESSING_BIT       1
 };
 
 struct qed_mcp_mb_params {