diff options
| author | David Brownell <david-b@pacbell.net> | 2007-07-22 15:13:13 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2007-07-30 13:27:45 -0700 |
| commit | a12b8db02035673153bbf19bb3641a08bed9e4b8 (patch) | |
| tree | c168c7816fb9da3e3a1596f42c1def295addf77b | |
| parent | e31c18804f584dd838a752f6628e8c15bd7a3372 (diff) | |
USB: fix scatterlist PIO case (IOMMU)
Update the scatterlist logic so that PIO options are also disabled
when an IOMMU may have coalesced pages during dma_map_sg() ... it's
not just HIGHMEM that can make trouble supporting both PIO and DMA
based host controller drivers.
There also seems to be a cross-arch issue here, with 64bit powerpc
not using an IOMMU define ... and its IOMMU_VMERGE config can always
be overridden on the kernel command line. So this is better, but
still imperfect.
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
| -rw-r--r-- | drivers/usb/core/message.c | 15 |
1 files changed, 11 insertions, 4 deletions
diff --git a/drivers/usb/core/message.c b/drivers/usb/core/message.c index 25f63f1096b4..ad4b956380d2 100644 --- a/drivers/usb/core/message.c +++ b/drivers/usb/core/message.c @@ -411,15 +411,22 @@ int usb_sg_init ( * Some systems need to revert to PIO when DMA is temporarily * unavailable. For their sakes, both transfer_buffer and * transfer_dma are set when possible. However this can only - * work on systems without HIGHMEM, since DMA buffers located - * in high memory are not directly addressable by the CPU for - * PIO ... so when HIGHMEM is in use, transfer_buffer is NULL + * work on systems without: + * + * - HIGHMEM, since DMA buffers located in high memory are + * not directly addressable by the CPU for PIO; + * + * - IOMMU, since dma_map_sg() is allowed to use an IOMMU to + * make virtually discontiguous buffers be "dma-contiguous" + * so that PIO and DMA need diferent numbers of URBs. + * + * So when HIGHMEM or IOMMU are in use, transfer_buffer is NULL * to prevent stale pointers and to help spot bugs. */ if (dma) { io->urbs [i]->transfer_dma = sg_dma_address (sg + i); len = sg_dma_len (sg + i); -#ifdef CONFIG_HIGHMEM +#if defined(CONFIG_HIGHMEM) || defined(CONFIG_IOMMU) io->urbs[i]->transfer_buffer = NULL; #else io->urbs[i]->transfer_buffer = |