From d50314a6b0702c630c35b88148c1acb76d2e4ede Mon Sep 17 00:00:00 2001 From: Catalin Marinas Date: Fri, 18 Jul 2014 11:54:37 +0100 Subject: [PATCH] arm64: Create non-empty ZONE_DMA when DRAM starts above 4GB ZONE_DMA is created to allow 32-bit only devices to access memory in the absence of an IOMMU. On systems where the memory starts above 4GB, it is expected that some devices have a DMA offset hardwired to be able to access the bottom of the memory. Linux currently supports DT bindings for the DMA offsets but they are not (easily) available early during boot. This patch tries to guess a DMA offset and assumes that ZONE_DMA corresponds to the 32-bit mask above the start of DRAM. Fixes: 2d5a5612bc (arm64: Limit the CMA buffer to 32-bit if ZONE_DMA) Signed-off-by: Catalin Marinas Reported-by: Mark Salter Tested-by: Mark Salter Tested-by: Anup Patel --- arch/arm64/mm/init.c | 17 +++++++++++++---- 1 file changed, 13 insertions(+), 4 deletions(-) diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c index f43db8a69262..e90c5426fe14 100644 --- a/arch/arm64/mm/init.c +++ b/arch/arm64/mm/init.c @@ -60,6 +60,17 @@ static int __init early_initrd(char *p) early_param("initrd", early_initrd); #endif +/* + * Return the maximum physical address for ZONE_DMA (DMA_BIT_MASK(32)). It + * currently assumes that for memory starting above 4G, 32-bit devices will + * use a DMA offset. + */ +static phys_addr_t max_zone_dma_phys(void) +{ + phys_addr_t offset = memblock_start_of_DRAM() & GENMASK_ULL(63, 32); + return min(offset + (1ULL << 32), memblock_end_of_DRAM()); +} + static void __init zone_sizes_init(unsigned long min, unsigned long max) { struct memblock_region *reg; @@ -70,9 +81,7 @@ static void __init zone_sizes_init(unsigned long min, unsigned long max) /* 4GB maximum for 32-bit only capable devices */ if (IS_ENABLED(CONFIG_ZONE_DMA)) { - unsigned long max_dma_phys = - (unsigned long)(dma_to_phys(NULL, DMA_BIT_MASK(32)) + 1); - max_dma = max(min, min(max, max_dma_phys >> PAGE_SHIFT)); + max_dma = PFN_DOWN(max_zone_dma_phys()); zone_size[ZONE_DMA] = max_dma - min; } zone_size[ZONE_NORMAL] = max - max_dma; @@ -146,7 +155,7 @@ void __init arm64_memblock_init(void) /* 4GB maximum for 32-bit only capable devices */ if (IS_ENABLED(CONFIG_ZONE_DMA)) - dma_phys_limit = dma_to_phys(NULL, DMA_BIT_MASK(32)) + 1; + dma_phys_limit = max_zone_dma_phys(); dma_contiguous_reserve(dma_phys_limit); memblock_allow_resize(); -- 2.41.0