On some 64-bit DMA engines (my BCM4331, at least) with a ring buffer
that is not aligned to 8KiB, we often see bit 12 spuriously being set in
the B43_DMA64_RXSTATUS register. This will happen the first time the
ring fills and loops back to zero:
[35755.186080] Read RXSTATUS 3f0 (makes offs 3f0, divided by 10 gives slot 3f
[35755.288366] Read RXSTATUS 1000 (makes offs 1000, divided by 10 gives slot 100
[35755.291007] ------------[ cut here ]------------
[35755.291041] WARNING: at drivers/net/wireless/b43/dma.c:1700
b43_dma_rx+0x5e/0x2df [b43]()
...
[35766.745374] b43-phy41 debug: DMA RX: Dropping poisoned buffer.
All we need to do is mask the offending bit out. The packets *are* where
they should be; it's just the high bit of the reported offset which is
weird.
Signed-off-by: David Woodhouse <david.woodho...@intel.com>
diff --git a/drivers/net/wireless/b43/dma.c b/drivers/net/wireless/b43/dma.c
index 82168f8..92dd6d9 100644
--- a/drivers/net/wireless/b43/dma.c
+++ b/drivers/net/wireless/b43/dma.c
@@ -247,6 +249,10 @@ static int op64_get_current_rxslot(struct b43_dmaring
*ring)
val = b43_dma_read(ring, B43_DMA64_RXSTATUS);
val &= B43_DMA64_RXSTATDPTR;
+ /* When the ring is not aligned to 8KiB, we sometimes get
+ bit 12 (0x1000) set in the address. Mask it out; we
+ only use a 4KiB ring. */
+ val &= B43_DMA_RINGMEMSIZE-1;
return (val / sizeof(struct b43_dmadesc64));
}
--
David Woodhouse Open Source Technology Centre
david.woodho...@intel.com Intel Corporation
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