b43: use 8K buffers for 64-bit DMA to workaround hardware bug

Signed-off-by: Rafał Miłecki <zajec5@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

2 files changed, 18 insertions, 9 deletions

diff --git a/drivers/net/wireless/b43/dma.c b/drivers/net/wireless/b43/dma.c
index c83c4b64c60e..975d96040548 100644
--- a/drivers/net/wireless/b43/dma.c
+++ b/drivers/net/wireless/b43/dma.c
@@ -419,26 +419,34 @@ static int alloc_ringmemory(struct b43_dmaring *ring)
         gfp_t flags = GFP_KERNEL;
 
         /* The specs call for 4K buffers for 30- and 32-bit DMA with 4K
-         * alignment and 8K buffers for 64-bit DMA with 8K alignment. Testing
-         * has shown that 4K is sufficient for the latter as long as the buffer
-         * does not cross an 8K boundary.
-         *
+         * alignment and 8K buffers for 64-bit DMA with 8K alignment.
+         * In practice we could use smaller buffers for the latter, but the
+         * alignment is really important because of the hardware bug. If bit
+         * 0x00001000 is used in DMA address, some hardware (like BCM4331)
+         * copies that bit into B43_DMA64_RXSTATUS and we get false values from
+         * B43_DMA64_RXSTATDPTR. Let's just use 8K buffers even if we don't use
+         * more than 256 slots for ring.
          */
+        u16 ring_mem_size = (ring->type == B43_DMA_64BIT) ?
+                                B43_DMA64_RINGMEMSIZE : B43_DMA32_RINGMEMSIZE;
+
         ring->descbase = dma_alloc_coherent(ring->dev->dev->dma_dev,
-                                            B43_DMA_RINGMEMSIZE,
-                                            &(ring->dmabase), flags);
+                                            ring_mem_size, &(ring->dmabase),
+                                            flags);
         if (!ring->descbase) {
                 b43err(ring->dev->wl, "DMA ringmemory allocation failed\n");
                 return -ENOMEM;
         }
-        memset(ring->descbase, 0, B43_DMA_RINGMEMSIZE);
+        memset(ring->descbase, 0, ring_mem_size);
 
         return 0;
 }
 
 static void free_ringmemory(struct b43_dmaring *ring)
 {
-        dma_free_coherent(ring->dev->dev->dma_dev, B43_DMA_RINGMEMSIZE,
+        u16 ring_mem_size = (ring->type == B43_DMA_64BIT) ?
+                                B43_DMA64_RINGMEMSIZE : B43_DMA32_RINGMEMSIZE;
+        dma_free_coherent(ring->dev->dev->dma_dev, ring_mem_size,
                           ring->descbase, ring->dmabase);
 }
 
diff --git a/drivers/net/wireless/b43/dma.h b/drivers/net/wireless/b43/dma.h
index 7e20b04fa51a..315b96ed1d90 100644
--- a/drivers/net/wireless/b43/dma.h
+++ b/drivers/net/wireless/b43/dma.h
@@ -161,7 +161,8 @@ struct b43_dmadesc_generic {
 } __packed;
 
 /* Misc DMA constants */
-#define B43_DMA_RINGMEMSIZE             PAGE_SIZE
+#define B43_DMA32_RINGMEMSIZE           4096
+#define B43_DMA64_RINGMEMSIZE           8192
 /* Offset of frame with actual data */
 #define B43_DMA0_RX_FW598_FO            38
 #define B43_DMA0_RX_FW351_FO            30