From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 42GQq76csyzF3Ng for ; Fri, 21 Sep 2018 04:53:20 +1000 (AEST) From: Christoph Hellwig To: iommu@lists.linux-foundation.org Cc: Marek Szyprowski , Robin Murphy , Benjamin Herrenschmidt , Greg Kroah-Hartman , linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org Subject: [PATCH 5/5] dma-direct: always allow dma mask <= physiscal memory size Date: Thu, 20 Sep 2018 20:52:47 +0200 Message-Id: <20180920185247.20037-6-hch@lst.de> In-Reply-To: <20180920185247.20037-1-hch@lst.de> References: <20180920185247.20037-1-hch@lst.de> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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 --- 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 64466b7ef67b..d1e103c6b107 100644 --- a/kernel/dma/direct.c +++ b/kernel/dma/direct.c @@ -4,6 +4,7 @@ * * DMA operations that map physical memory directly without using an IOMMU. */ +#include /* for max_pfn */ #include #include #include @@ -283,21 +284,24 @@ 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))) - 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))) + u64 min_mask; + + if (IS_ENABLED(CONFIG_ZONE_DMA)) + min_mask = DMA_BIT_MASK(ARCH_ZONE_DMA_BITS); + else + min_mask = min_t(u64, DMA_BIT_MASK(32), + (max_pfn - 1) << PAGE_SHIFT); + + if (mask >= phys_to_dma(dev, min_mask)) return 0; -#endif return 1; } -- 2.18.0