From: Joonsoo Kim <[email protected]> CMA region is now managed by the separate zone, ZONE_CMA, to fix many MM related problems. In this implementation, it is possible that ZONE_CMA contains two CMA regions that are on the both, lowmem and highmem, respectively. To handle this case properly, ZONE_CMA is considered as highmem.
In dma_contiguous_remap(), mapping for CMA region on lowmem is cleared and remapped for DMA, but, in the new CMA implementation, remap isn't needed since the region is considered as highmem. And, remap should not be allowed since it would cause cache problems. So, this patch disables it. Signed-off-by: Joonsoo Kim <[email protected]> --- arch/arm/mm/dma-mapping.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c index 475811f..377053a 100644 --- a/arch/arm/mm/dma-mapping.c +++ b/arch/arm/mm/dma-mapping.c @@ -506,7 +506,12 @@ void __init dma_contiguous_remap(void) flush_tlb_kernel_range(__phys_to_virt(start), __phys_to_virt(end)); - iotable_init(&map, 1); + /* + * For highmem system, all the memory in CMA region will be + * considered as highmem, therefore, re-mapping isn't required. + */ + if (!IS_ENABLED(CONFIG_HIGHMEM)) + iotable_init(&map, 1); } } -- 2.7.4
