USB: fix scatterlist PIO case (IOMMU) (a12b8db0) · Commits · 戴 / test

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>

drivers/usb/core/message.c

+11 −4

Original line number	Diff line number	Diff line
		@@ -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 =

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