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staging: brcm80211: added clarification on softmac dma alignment

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Descriptor ring can only start at 8KB alignment, this requirement
is dictated by DMA hardware.

Reported-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Roland Vossen <rvossen@broadcom.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Roland Vossen
2011-09-13 09:49:49 +02:00
committed by Greg Kroah-Hartman
parent 7d9e0b9a7f
commit 5b876618c0
1 changed files with 6 additions and 2 deletions
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8
drivers/staging/brcm80211/brcmsmac/dma.c
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@@ -24,8 +24,8 @@
#include "dma.h" #include "dma.h"
/* /*
* Each descriptor ring must be 8kB aligned, and fit within a * DMA hardware requires each descriptor ring to be 8kB aligned, and fit within
* contiguous 8kB physical address. * a contiguous 8kB physical address.
*/ */
#define D64RINGALIGN_BITS 13 #define D64RINGALIGN_BITS 13
#define D64MAXRINGSZ (1 << D64RINGALIGN_BITS) #define D64MAXRINGSZ (1 << D64RINGALIGN_BITS)
@@ -440,6 +440,10 @@ static bool _dma_descriptor_align(struct dma_info *di)
return true; return true;
} }
/*
* Descriptor table must start at the DMA hardware dictated alignment, so
* allocated memory must be large enough to support this requirement.
*/
static void *dma_alloc_consistent(struct pci_dev *pdev, uint size, static void *dma_alloc_consistent(struct pci_dev *pdev, uint size,
u16 align_bits, uint *alloced, u16 align_bits, uint *alloced,
dma_addr_t *pap) dma_addr_t *pap)