| From f3cc4e1d44a813a0685f2e558b78ace3db559722 Mon Sep 17 00:00:00 2001 |
| From: Chen-Yu Tsai <wens@csie.org> |
| Date: Mon, 3 Feb 2020 17:37:48 -0800 |
| Subject: ARM: dma-api: fix max_pfn off-by-one error in __dma_supported() |
| |
| From: Chen-Yu Tsai <wens@csie.org> |
| |
| commit f3cc4e1d44a813a0685f2e558b78ace3db559722 upstream. |
| |
| max_pfn, as set in arch/arm/mm/init.c: |
| |
| static void __init find_limits(unsigned long *min, |
| unsigned long *max_low, |
| unsigned long *max_high) |
| { |
| *max_low = PFN_DOWN(memblock_get_current_limit()); |
| *min = PFN_UP(memblock_start_of_DRAM()); |
| *max_high = PFN_DOWN(memblock_end_of_DRAM()); |
| } |
| |
| with memblock_end_of_DRAM() pointing to the next byte after DRAM. As |
| such, max_pfn points to the PFN after the end of DRAM. |
| |
| Thus when using max_pfn to check DMA masks, we should subtract one when |
| checking DMA ranges against it. |
| |
| Commit 8bf1268f48ad ("ARM: dma-api: fix off-by-one error in |
| __dma_supported()") fixed the same issue, but missed this spot. |
| |
| This issue was found while working on the sun4i-csi v4l2 driver on the |
| Allwinner R40 SoC. On Allwinner SoCs, DRAM is offset at 0x40000000, and |
| we are starting to use of_dma_configure() with the "dma-ranges" property |
| in the device tree to have the DMA API handle the offset. |
| |
| In this particular instance, dma-ranges was set to the same range as the |
| actual available (2 GiB) DRAM. The following error appeared when the |
| driver attempted to allocate a buffer: |
| |
| sun4i-csi 1c09000.csi: Coherent DMA mask 0x7fffffff (pfn 0x40000-0xc0000) |
| covers a smaller range of system memory than the DMA zone pfn 0x0-0xc0001 |
| sun4i-csi 1c09000.csi: dma_alloc_coherent of size 307200 failed |
| |
| Fixing the off-by-one error makes things work. |
| |
| Link: http://lkml.kernel.org/r/20191224030239.5656-1-wens@kernel.org |
| Fixes: 11a5aa32562e ("ARM: dma-mapping: check DMA mask against available memory") |
| Fixes: 9f28cde0bc64 ("ARM: another fix for the DMA mapping checks") |
| Fixes: ab746573c405 ("ARM: dma-mapping: allow larger DMA mask than supported") |
| Signed-off-by: Chen-Yu Tsai <wens@csie.org> |
| Reviewed-by: Christoph Hellwig <hch@lst.de> |
| Cc: Russell King <linux@armlinux.org.uk> |
| Cc: Robin Murphy <robin.murphy@arm.com> |
| Cc: <stable@vger.kernel.org> |
| Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
| Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| arch/arm/mm/dma-mapping.c | 2 +- |
| 1 file changed, 1 insertion(+), 1 deletion(-) |
| |
| --- a/arch/arm/mm/dma-mapping.c |
| +++ b/arch/arm/mm/dma-mapping.c |
| @@ -221,7 +221,7 @@ EXPORT_SYMBOL(arm_coherent_dma_ops); |
| |
| static int __dma_supported(struct device *dev, u64 mask, bool warn) |
| { |
| - unsigned long max_dma_pfn = min(max_pfn, arm_dma_pfn_limit); |
| + unsigned long max_dma_pfn = min(max_pfn - 1, arm_dma_pfn_limit); |
| |
| /* |
| * Translate the device's DMA mask to a PFN limit. This |