arm64: mm: only initialize swiotlb when necessary

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 <jszhang@marvell.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c
index c566ec83719f6bb07fe909f02900a8ab885698de..46a4157adc17fd11189cfc7383e12ff5f9441033 100644 (file)
--- 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 d45f8627012c0610c4d62e54c11eacd8007c5f52..7d25b4d006779bb593d46f397528678e4066f656 100644 (file)
--- 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);