we only initialize swiotlb when swiotlb_force is true or not all system memory is DMA-able, this trivial optimization saves us 64MB when swiotlb is not necessary.
Signed-off-by: Jisheng Zhang <[email protected]> --- arch/arm64/mm/dma-mapping.c | 15 ++++++++++++++- arch/arm64/mm/init.c | 3 ++- 2 files changed, 16 insertions(+), 2 deletions(-) diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c index c566ec8..46a4157 100644 --- a/arch/arm64/mm/dma-mapping.c +++ b/arch/arm64/mm/dma-mapping.c @@ -19,6 +19,7 @@ #include <linux/gfp.h> #include <linux/acpi.h> +#include <linux/bootmem.h> #include <linux/export.h> #include <linux/slab.h> #include <linux/genalloc.h> @@ -29,6 +30,8 @@ #include <asm/cacheflush.h> +static int swiotlb __read_mostly; + static pgprot_t __get_dma_pgprot(struct dma_attrs *attrs, pgprot_t prot, bool coherent) { @@ -341,6 +344,13 @@ static int __swiotlb_get_sgtable(struct device *dev, struct sg_table *sgt, return ret; } +static int __swiotlb_dma_supported(struct device *hwdev, u64 mask) +{ + if (swiotlb) + return swiotlb_dma_supported(hwdev, mask); + return 1; +} + static struct dma_map_ops swiotlb_dma_ops = { .alloc = __dma_alloc, .free = __dma_free, @@ -354,7 +364,7 @@ static struct dma_map_ops swiotlb_dma_ops = { .sync_single_for_device = __swiotlb_sync_single_for_device, .sync_sg_for_cpu = __swiotlb_sync_sg_for_cpu, .sync_sg_for_device = __swiotlb_sync_sg_for_device, - .dma_supported = swiotlb_dma_supported, + .dma_supported = __swiotlb_dma_supported, .mapping_error = swiotlb_dma_mapping_error, }; @@ -513,6 +523,9 @@ EXPORT_SYMBOL(dummy_dma_ops); static int __init arm64_dma_init(void) { + if (swiotlb_force || max_pfn > (arm64_dma_phys_limit >> PAGE_SHIFT)) + swiotlb = 1; + return atomic_pool_init(); } arch_initcall(arm64_dma_init); diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c index d45f862..7d25b4d 100644 --- a/arch/arm64/mm/init.c +++ b/arch/arm64/mm/init.c @@ -403,7 +403,8 @@ static void __init free_unused_memmap(void) */ void __init mem_init(void) { - swiotlb_init(1); + if (swiotlb_force || max_pfn > (arm64_dma_phys_limit >> PAGE_SHIFT)) + swiotlb_init(1); set_max_mapnr(pfn_to_page(max_pfn) - mem_map); -- 2.8.1
