1 files changed, 19 insertions, 4 deletions

diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 091d428d64ac..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;
@@ -126,6 +135,8 @@ static void arm64_memory_present(void)
 
 void __init arm64_memblock_init(void)
 {
+        phys_addr_t dma_phys_limit = 0;
+
         /* Register the kernel text, kernel data and initrd with memblock */
         memblock_reserve(__pa(_text), _end - _text);
 #ifdef CONFIG_BLK_DEV_INITRD
@@ -141,7 +152,11 @@ void __init arm64_memblock_init(void)
         memblock_reserve(__pa(idmap_pg_dir), IDMAP_DIR_SIZE);
 
         early_init_fdt_scan_reserved_mem();
-        dma_contiguous_reserve(0);
+
+        /* 4GB maximum for 32-bit only capable devices */
+        if (IS_ENABLED(CONFIG_ZONE_DMA))
+                dma_phys_limit = max_zone_dma_phys();
+        dma_contiguous_reserve(dma_phys_limit);
 
         memblock_allow_resize();
         memblock_dump_all();