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Commit a12b8db0 authored by David Brownell's avatar David Brownell Committed by Greg Kroah-Hartman
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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: default avatarDavid Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent e31c1880

drivers/usb/core/message.c

+11 −4
Original line number Original line Diff line number Diff line
@@ -411,15 +411,22 @@ int usb_sg_init ( 
		 * Some systems need to revert to PIO when DMA is temporarily

		 * Some systems need to revert to PIO when DMA is temporarily

		 * unavailable.  For their sakes, both transfer_buffer and

		 * unavailable.  For their sakes, both transfer_buffer and

		 * transfer_dma are set when possible.  However this can only

		 * transfer_dma are set when possible.  However this can only

		 * work on systems without HIGHMEM, since DMA buffers located

		 * work on systems without:

		 * in high memory are not directly addressable by the CPU for

		 *

		 * PIO ... so when HIGHMEM is in use, transfer_buffer is NULL

		 *  - 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.

		 * to prevent stale pointers and to help spot bugs.

		 */

		 */

		if (dma) {

		if (dma) {

			io->urbs [i]->transfer_dma = sg_dma_address (sg + i);

			io->urbs [i]->transfer_dma = sg_dma_address (sg + i);

			len = sg_dma_len (sg + i);

			len = sg_dma_len (sg + i);

#ifdef CONFIG_HIGHMEM

#if defined(CONFIG_HIGHMEM) || defined(CONFIG_IOMMU)

			io->urbs[i]->transfer_buffer = NULL;

			io->urbs[i]->transfer_buffer = NULL;

#else

#else

			io->urbs[i]->transfer_buffer =

			io->urbs[i]->transfer_buffer =