Unverified Commit d411da06 authored Feb 15, 2019 by Paul Burton

MIPS: dma-noncoherent: Remove bogus condition in dma_sync_phys()



Commit e36863a5 ("MIPS: HIGHMEM DMA on noncoherent MIPS32
processors") introduced code which:

  1) Calculates an offset within a page, by ANDing an address
     with ~PAGE_MASK.

  2) Checks whether that offset is >= PAGE_SIZE.

This check can never evaluate true, making the code it guards
unreachable. smatch spots bogus arithmetic resulting from the
impossible condition, resulting in the following warning:

  arch/mips/mm/dma-noncoherent.c:125
    dma_sync_phys() warn: mask and shift to zero

Fix this by removing the impossible to satisfy condition & the
unreachable code it guards.

Signed-off-by: Paul Burton <paul.burton@mips.com>
Cc: linux-mips@vger.kernel.org
Cc: Christoph Hellwig <hch@lst.de>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Robin Murphy <robin.murphy@arm.com>

parent 66b6572a

arch/mips/mm/dma-noncoherent.c

+1 −6

Original line number	Diff line number	Diff line
		@@ -120,13 +120,8 @@ static inline void dma_sync_phys(phys_addr_t paddr, size_t size,
		if (PageHighMem(page)) {
		void *addr;

		if (offset + len > PAGE_SIZE) {
		if (offset >= PAGE_SIZE) {
		page += offset >> PAGE_SHIFT;
		offset &= ~PAGE_MASK;
		}
		if (offset + len > PAGE_SIZE)
		len = PAGE_SIZE - offset;
		}

		addr = kmap_atomic(page);
		dma_sync_virt(addr + offset, len, dir);

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