From 3cb50076ba3fcd25754d9efe583a918d3b365473 Mon Sep 17 00:00:00 2001 From: Santosh Shilimkar Date: Mon, 29 Jul 2013 14:18:48 +0100 Subject: [PATCH] ARM: 7795/1: mm: dma-mapping: Add dma_max_pfn(dev) helper function Most of the kernel assumes that PFN0 is the start of the physical memory (RAM). This assumptions is not true on most of the ARM SOCs and hence and if one try to update the ARM port to follow the assumptions, we end of breaking the dma bounce limit for few block layer drivers. One such example is trying to unify the meaning of max*_pfn on ARM as the bootmem layer expects, breaks few block layer driver dma bounce limit. To fix this problem, we introduce dma_max_pfn(dev) generic helper with a possibility of override from the architecture code. The helper converts a DMA bitmask of bits to a block PFN number. In all the generic cases, it is just "dev->dma_mask >> PAGE_SHIFT" and hence default behavior is maintained as is. Subsequent patches will make use of the helper. No functional change. Cc: Jens Axboe Signed-off-by: Santosh Shilimkar Signed-off-by: Russell King --- include/linux/dma-mapping.h | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h index 94af41858513..68a7863393b0 100644 --- a/include/linux/dma-mapping.h +++ b/include/linux/dma-mapping.h @@ -129,6 +129,13 @@ static inline int dma_set_seg_boundary(struct device *dev, unsigned long mask) return -EIO; } +#ifndef dma_max_pfn +static inline unsigned long dma_max_pfn(struct device *dev) +{ + return *dev->dma_mask >> PAGE_SHIFT; +} +#endif + static inline void *dma_zalloc_coherent(struct device *dev, size_t size, dma_addr_t *dma_handle, gfp_t flag) { -- 2.34.1