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>

1 files changed, 39 insertions, 8 deletions

diff --git a/drivers/net/wireless/b43/dma.c b/drivers/net/wireless/b43/dma.c
index 21c886a9a1d9..6dcbb3c87e72 100644
--- 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. */