B43: Handle DMA RX descriptor underrun

Add handling of rx descriptor underflow. This fixes a fault that could
happen on slow machines, where data is received faster than the CPU can
handle. In such a case the device will use up all rx descriptors and
refuse to send any more data before confirming that it is ok. This
patch enables necessary interrupt to discover such a situation and will
handle them by dropping everything in the ring buffer.

Reviewed-by: Michael Buesch <m@bues.ch>
Signed-off-by: Thommy Jakobsson <thommyj@gmail.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 19 insertions, 0 deletions

diff --git a/drivers/net/wireless/b43/dma.c b/drivers/net/wireless/b43/dma.c
index 1221469..ee3d640 100644
--- a/drivers/net/wireless/b43/dma.c
+++ b/drivers/net/wireless/b43/dma.c
@@ -1733,6 +1733,25 @@ drop_recycle_buffer:
 	sync_descbuffer_for_device(ring, dmaaddr, ring->rx_buffersize);
 }
 
+void b43_dma_handle_rx_overflow(struct b43_dmaring *ring)
+{
+	int current_slot, previous_slot;
+
+	B43_WARN_ON(ring->tx);
+
+	/* Device has filled all buffers, drop all packets and let TCP
+	 * decrease speed.
+	 * Decrement RX index by one will let the device to see all slots
+	 * as free again
+	 */
+	/*
+	*TODO: How to increase rx_drop in mac80211?
+	*/
+	current_slot = ring->ops->get_current_rxslot(ring);
+	previous_slot = prev_slot(ring, current_slot);
+	ring->ops->set_current_rxslot(ring, previous_slot);
+}
+
 void b43_dma_rx(struct b43_dmaring *ring)
 {
 	const struct b43_dma_ops *ops = ring->ops;