--- 9ca253e40bd5e8cceb7fc1dfbad4837bf368a11e
+++ d6056347b6bdbe146f612b88a7a0f87816c4e79d
@@ -102,6 +102,9 @@ int b43_modparam_verbose = B43_VERBOSITY
 module_param_named(verbose, b43_modparam_verbose, int, 0644);
 MODULE_PARM_DESC(verbose, "Log message verbosity: 0=error, 1=warn, 2=info(default), 3=debug");
 
+int b43_modparam_pio = B43_PIO_DEFAULT;
+module_param_named(pio, b43_modparam_pio, int, 0644);
+MODULE_PARM_DESC(pio, "Use PIO accesses by default: 0=DMA, 1=PIO");
 
 static const struct ssb_device_id b43_ssb_tbl[] = {
 	SSB_DEVICE(SSB_VENDOR_BROADCOM, SSB_DEV_80211, 5),
@@ -852,19 +855,16 @@ static void b43_op_update_tkip_key(struc
 	if (B43_WARN_ON(!modparam_hwtkip))
 		return;
 
-	mutex_lock(&wl->mutex);
-
+	/* This is only called from the RX path through mac80211, where
+	 * our mutex is already locked. */
+	B43_WARN_ON(!mutex_is_locked(&wl->mutex));
 	dev = wl->current_dev;
-	if (!dev || b43_status(dev) < B43_STAT_INITIALIZED)
-		goto out_unlock;
+	B43_WARN_ON(!dev || b43_status(dev) < B43_STAT_INITIALIZED);
 
 	keymac_write(dev, index, NULL);	/* First zero out mac to avoid race */
 
 	rx_tkip_phase1_write(dev, index, iv32, phase1key);
 	keymac_write(dev, index, addr);
-
-out_unlock:
-	mutex_unlock(&wl->mutex);
 }
 
 static void do_key_write(struct b43_wldev *dev,
@@ -1791,6 +1791,10 @@ static void b43_do_interrupt_thread(stru
 			       dma_reason[0], dma_reason[1],
 			       dma_reason[2], dma_reason[3],
 			       dma_reason[4], dma_reason[5]);
+			b43err(dev->wl, "This device does not support DMA "
+			       "on your system. Please use PIO instead.\n");
+			/* Fall back to PIO transfers if we get fatal DMA errors! */
+			dev->use_pio = 1;
 			b43_controller_restart(dev, "DMA error");
 			return;
 		}
@@ -3967,6 +3971,7 @@ static int b43_wireless_core_start(struc
 	}
 
 	/* We are ready to run. */
+	ieee80211_wake_queues(dev->wl->hw);
 	b43_set_status(dev, B43_STAT_STARTED);
 
 	/* Start data flow (TX/RX). */
@@ -4357,7 +4362,7 @@ static int b43_wireless_core_init(struct
 
 	if ((dev->dev->bus->bustype == SSB_BUSTYPE_PCMCIA) ||
 	    (dev->dev->bus->bustype == SSB_BUSTYPE_SDIO) ||
-	    B43_FORCE_PIO) {
+	    dev->use_pio) {
 		dev->__using_pio_transfers = 1;
 		err = b43_pio_init(dev);
 	} else {
@@ -4376,8 +4381,6 @@ static int b43_wireless_core_init(struct
 
 	ieee80211_wake_queues(dev->wl->hw);
 
-	ieee80211_wake_queues(dev->wl->hw);
-
 	b43_set_status(dev, B43_STAT_INITIALIZED);
 
 out:
@@ -4827,6 +4830,7 @@ static int b43_one_core_attach(struct ss
 	if (!wldev)
 		goto out;
 
+	wldev->use_pio = b43_modparam_pio;
 	wldev->dev = dev;
 	wldev->wl = wl;
 	b43_set_status(wldev, B43_STAT_UNINIT);