b43: Workaround DMA quirks

Some mainboards/CPUs don't allow DMA masks bigger than a certain limit.
Some VIA crap^h^h^h^hdevices have an upper limit of 0xFFFFFFFF. So in this
case a 64-bit b43 device would always fail to acquire the mask.
Implement a workaround to fallback to lower DMA mask, as we can always
also support a lower mask.

Signed-off-by: Michael Buesch <mb@bu3sch.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

diff --git a/drivers/net/wireless/b43/dma.c b/drivers/net/wireless/b43/dma.c
index 21c886a9a1d96a85b79e30890379d67c6c5db8eb..6dcbb3c87e7207a01cf64f2269f3cea1438cfe04 100644 (file)
--- a/drivers/net/wireless/b43/dma.c
+++ b/drivers/net/wireless/b43/dma.c
@@ -980,6 +980,42 @@ void b43_dma_free(struct b43_wldev *dev)
        destroy_ring(dma, tx_ring_mcast);
 }
 
+static int b43_dma_set_mask(struct b43_wldev *dev, u64 mask)
+{
+       u64 orig_mask = mask;
+       bool fallback = 0;
+       int err;
+
+       /* Try to set the DMA mask. If it fails, try falling back to a
+        * lower mask, as we can always also support a lower one. */
+       while (1) {
+               err = ssb_dma_set_mask(dev->dev, mask);
+               if (!err)
+                       break;
+               if (mask == DMA_64BIT_MASK) {
+                       mask = DMA_32BIT_MASK;
+                       fallback = 1;
+                       continue;
+               }
+               if (mask == DMA_32BIT_MASK) {
+                       mask = DMA_30BIT_MASK;
+                       fallback = 1;
+                       continue;
+               }
+               b43err(dev->wl, "The machine/kernel does not support "
+                      "the required %u-bit DMA mask\n",
+                      (unsigned int)dma_mask_to_engine_type(orig_mask));
+               return -EOPNOTSUPP;
+       }
+       if (fallback) {
+               b43info(dev->wl, "DMA mask fallback from %u-bit to %u-bit\n",
+                       (unsigned int)dma_mask_to_engine_type(orig_mask),
+                       (unsigned int)dma_mask_to_engine_type(mask));
+       }
+
+       return 0;
+}
+
 int b43_dma_init(struct b43_wldev *dev)
 {
        struct b43_dma *dma = &dev->dma;
@@ -989,14 +1025,9 @@ int b43_dma_init(struct b43_wldev *dev)
 
        dmamask = supported_dma_mask(dev);
        type = dma_mask_to_engine_type(dmamask);
-       err = ssb_dma_set_mask(dev->dev, dmamask);
-       if (err) {
-               b43err(dev->wl, "The machine/kernel does not support "
-                      "the required DMA mask (0x%08X%08X)\n",
-                      (unsigned int)((dmamask & 0xFFFFFFFF00000000ULL) >> 32),
-                      (unsigned int)(dmamask & 0x00000000FFFFFFFFULL));
-               return -EOPNOTSUPP;
-       }
+       err = b43_dma_set_mask(dev, dmamask);
+       if (err)
+               return err;
 
        err = -ENOMEM;
        /* setup TX DMA channels. */