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

	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);

}

} __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