staging: wilc1000: avoid mutex unlock without lock in wilc_wlan_handle_txq()

In wilc_wlan_handle_txq(), mutex unlock was called without acquiring
it. Also error code for full VMM condition was incorrect as discussed in
[1]. Now used a proper code to indicate VMM is full, for which transfer
to VMM is required again. 'wilc_wlan_handle_txq()' should be called
again if the VMM space was full earlier or otherwise based on
'txq_event' signal.

1. https://lore.kernel.org/driverdev-devel/20191113183322.a54mh2w6dulklgsd@kili.mountain/

Signed-off-by: Ajay Singh <ajay.kathat@microchip.com>
Link: https://lore.kernel.org/r/20200123182129.4053-2-ajay.kathat@microchip.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: ajaykathat

drivers/staging/wilc1000/netdev.c

@@ -174,7 +174,7 @@ static int wilc_txq_task(void *vp)
 				}
 				srcu_read_unlock(&wl->srcu, srcu_idx);
 			}
-		} while (ret == -ENOBUFS && !wl->close);
+		} while (ret == WILC_VMM_ENTRY_FULL_RETRY && !wl->close);
 	}
 	return 0;
 }

drivers/staging/wilc1000/wlan.c

@@ -489,12 +489,12 @@ int wilc_wlan_handle_txq(struct wilc *wilc, u32 *txq_count)
 	struct wilc_vif *vif;
 
 	if (wilc->quit)
-		goto out;
+		goto out_update_cnt;
 
 	mutex_lock(&wilc->txq_add_to_head_cs);
 	tqe = wilc_wlan_txq_get_first(wilc);
 	if (!tqe)
-		goto out;
+		goto out_unlock;
 	dev = tqe->vif->ndev;
 	wilc_wlan_txq_filter_dup_tcp_ack(dev);
 	i = 0;
@@ -526,7 +526,7 @@ int wilc_wlan_handle_txq(struct wilc *wilc, u32 *txq_count)
 	}
 
 	if (i == 0)
-		goto out;
+		goto out_unlock;
 	vmm_table[i] = 0x0;
 
 	acquire_bus(wilc, WILC_BUS_ACQUIRE_AND_WAKEUP);
@@ -595,7 +595,11 @@ int wilc_wlan_handle_txq(struct wilc *wilc, u32 *txq_count)
 		goto out_release_bus;
 
 	if (entries == 0) {
-		ret = -ENOBUFS;
+		/*
+		 * No VMM space available in firmware so retry to transmit
+		 * the packet from tx queue.
+		 */
+		ret = WILC_VMM_ENTRY_FULL_RETRY;
 		goto out_release_bus;
 	}
 
@@ -662,9 +666,10 @@ int wilc_wlan_handle_txq(struct wilc *wilc, u32 *txq_count)
 out_release_bus:
 	release_bus(wilc, WILC_BUS_RELEASE_ALLOW_SLEEP);
 
-out:
+out_unlock:
 	mutex_unlock(&wilc->txq_add_to_head_cs);
 
+out_update_cnt:
 	*txq_count = wilc->txq_entries;
 	return ret;
 }

drivers/staging/wilc1000/wlan.h

@@ -198,6 +198,7 @@
 #define IS_MGMT_STATUS_SUCCES	0x040
 
 #define WILC_WID_TYPE		GENMASK(15, 12)
+#define WILC_VMM_ENTRY_FULL_RETRY	1
 /********************************************
  *
  *      Tx/Rx Queue Structure