From 9d7a224b463e1cf1178570b57b6497240fd79bc3 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Fri, 7 Sep 2018 09:31:58 +0200 Subject: [PATCH] dma-direct: always allow dma mask <= physiscal memory size This way an architecture with less than 4G of RAM can support dma_mask smaller than 32-bit without a ZONE_DMA. Apparently that is a common case on powerpc. Signed-off-by: Christoph Hellwig Reviewed-by: Robin Murphy --- kernel/dma/direct.c | 28 ++++++++++++++++------------ 1 file changed, 16 insertions(+), 12 deletions(-) diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c index 60c433b880e0..170bd322a94a 100644 --- a/kernel/dma/direct.c +++ b/kernel/dma/direct.c @@ -284,21 +284,25 @@ int dma_direct_map_sg(struct device *dev, struct scatterlist *sgl, int nents, return nents; } +/* + * Because 32-bit DMA masks are so common we expect every architecture to be + * able to satisfy them - either by not supporting more physical memory, or by + * providing a ZONE_DMA32. If neither is the case, the architecture needs to + * use an IOMMU instead of the direct mapping. + */ int dma_direct_supported(struct device *dev, u64 mask) { -#ifdef CONFIG_ZONE_DMA - if (mask < phys_to_dma(dev, DMA_BIT_MASK(ARCH_ZONE_DMA_BITS))) + u64 min_mask; + + if (IS_ENABLED(CONFIG_ZONE_DMA)) + min_mask = DMA_BIT_MASK(ARCH_ZONE_DMA_BITS); + else + min_mask = DMA_BIT_MASK(32); + + min_mask = min_t(u64, min_mask, (max_pfn - 1) << PAGE_SHIFT); + + if (mask >= phys_to_dma(dev, min_mask)) return 0; -#else - /* - * Because 32-bit DMA masks are so common we expect every architecture - * to be able to satisfy them - either by not supporting more physical - * memory, or by providing a ZONE_DMA32. If neither is the case, the - * architecture needs to use an IOMMU instead of the direct mapping. - */ - if (mask < phys_to_dma(dev, DMA_BIT_MASK(32))) - return 0; -#endif return 1; }