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>

3 files changed, 40 insertions, 26 deletions

diff --git a/drivers/net/wireless/b43/dma.c b/drivers/net/wireless/b43/dma.c
index 122146943bf2..ee3d6403c795 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;
diff --git a/drivers/net/wireless/b43/dma.h b/drivers/net/wireless/b43/dma.h
index 9fdd1983079c..df8c8cdcbdb5 100644
--- a/drivers/net/wireless/b43/dma.h
+++ b/drivers/net/wireless/b43/dma.h
@@ -9,7 +9,7 @@
 /* DMA-Interrupt reasons. */
 #define B43_DMAIRQ_FATALMASK    ((1 << 10) | (1 << 11) | (1 << 12) \
                                          | (1 << 14) | (1 << 15))
-#define B43_DMAIRQ_NONFATALMASK (1 << 13)
+#define B43_DMAIRQ_RDESC_UFLOW          (1 << 13)
 #define B43_DMAIRQ_RX_DONE              (1 << 16)
 
 /*** 32-bit DMA Engine. ***/
@@ -295,6 +295,8 @@ int b43_dma_tx(struct b43_wldev *dev,
 void b43_dma_handle_txstatus(struct b43_wldev *dev,
                              const struct b43_txstatus *status);
 
+void b43_dma_handle_rx_overflow(struct b43_dmaring *ring);
+
 void b43_dma_rx(struct b43_dmaring *ring);
 
 void b43_dma_direct_fifo_rx(struct b43_wldev *dev,
diff --git a/drivers/net/wireless/b43/main.c b/drivers/net/wireless/b43/main.c
index d377f77d30b5..6dd07e2ec595 100644
--- a/drivers/net/wireless/b43/main.c
+++ b/drivers/net/wireless/b43/main.c
@@ -1902,30 +1902,18 @@ static void b43_do_interrupt_thread(struct b43_wldev *dev)
                 }
         }
 
-        if (unlikely(merged_dma_reason & (B43_DMAIRQ_FATALMASK |
-                                          B43_DMAIRQ_NONFATALMASK))) {
-                if (merged_dma_reason & B43_DMAIRQ_FATALMASK) {
-                        b43err(dev->wl, "Fatal DMA error: "
-                               "0x%08X, 0x%08X, 0x%08X, "
-                               "0x%08X, 0x%08X, 0x%08X\n",
-                               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 "
+        if (unlikely(merged_dma_reason & (B43_DMAIRQ_FATALMASK))) {
+                b43err(dev->wl,
+                        "Fatal DMA error: 0x%08X, 0x%08X, 0x%08X, 0x%08X, 0x%08X, 0x%08X\n",
+                        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. It will now be switched to PIO.\n");
-                        /* Fall back to PIO transfers if we get fatal DMA errors! */
-                        dev->use_pio = true;
-                        b43_controller_restart(dev, "DMA error");
-                        return;
-                }
-                if (merged_dma_reason & B43_DMAIRQ_NONFATALMASK) {
-                        b43err(dev->wl, "DMA error: "
-                               "0x%08X, 0x%08X, 0x%08X, "
-                               "0x%08X, 0x%08X, 0x%08X\n",
-                               dma_reason[0], dma_reason[1],
-                               dma_reason[2], dma_reason[3],
-                               dma_reason[4], dma_reason[5]);
-                }
+                /* Fall back to PIO transfers if we get fatal DMA errors! */
+                dev->use_pio = true;
+                b43_controller_restart(dev, "DMA error");
+                return;
         }
 
         if (unlikely(reason & B43_IRQ_UCODE_DEBUG))
@@ -1944,6 +1932,11 @@ static void b43_do_interrupt_thread(struct b43_wldev *dev)
                 handle_irq_noise(dev);
 
         /* Check the DMA reason registers for received data. */
+        if (dma_reason[0] & B43_DMAIRQ_RDESC_UFLOW) {
+                if (B43_DEBUG)
+                        b43warn(dev->wl, "RX descriptor underrun\n");
+                b43_dma_handle_rx_overflow(dev->dma.rx_ring);
+        }
         if (dma_reason[0] & B43_DMAIRQ_RX_DONE) {
                 if (b43_using_pio_transfers(dev))
                         b43_pio_rx(dev->pio.rx_queue);
@@ -2001,7 +1994,7 @@ static irqreturn_t b43_do_interrupt(struct b43_wldev *dev)
                 return IRQ_NONE;
 
         dev->dma_reason[0] = b43_read32(dev, B43_MMIO_DMA0_REASON)
-            & 0x0001DC00;
+            & 0x0001FC00;
         dev->dma_reason[1] = b43_read32(dev, B43_MMIO_DMA1_REASON)
             & 0x0000DC00;
         dev->dma_reason[2] = b43_read32(dev, B43_MMIO_DMA2_REASON)
@@ -3130,7 +3123,7 @@ static int b43_chip_init(struct b43_wldev *dev)
                 b43_write32(dev, 0x018C, 0x02000000);
         }
         b43_write32(dev, B43_MMIO_GEN_IRQ_REASON, 0x00004000);
-        b43_write32(dev, B43_MMIO_DMA0_IRQ_MASK, 0x0001DC00);
+        b43_write32(dev, B43_MMIO_DMA0_IRQ_MASK, 0x0001FC00);
         b43_write32(dev, B43_MMIO_DMA1_IRQ_MASK, 0x0000DC00);
         b43_write32(dev, B43_MMIO_DMA2_IRQ_MASK, 0x0000DC00);
         b43_write32(dev, B43_MMIO_DMA3_IRQ_MASK, 0x0001DC00);