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-rw-r--r--arch/arm64/mm/mmu.c42
1 files changed, 42 insertions, 0 deletions
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index a6885d896ab6..f4dd585898c5 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -25,6 +25,7 @@
#include <linux/nodemask.h>
#include <linux/memblock.h>
#include <linux/fs.h>
+#include <linux/io.h>
#include <asm/cputype.h>
#include <asm/sections.h>
@@ -251,6 +252,47 @@ static void __init create_mapping(phys_addr_t phys, unsigned long virt,
} while (pgd++, addr = next, addr != end);
}
+#ifdef CONFIG_EARLY_PRINTK
+/*
+ * Create an early I/O mapping using the pgd/pmd entries already populated
+ * in head.S as this function is called too early to allocated any memory. The
+ * mapping size is 2MB with 4KB pages or 64KB or 64KB pages.
+ */
+void __iomem * __init early_io_map(phys_addr_t phys, unsigned long virt)
+{
+ unsigned long size, mask;
+ bool page64k = IS_ENABLED(ARM64_64K_PAGES);
+ pgd_t *pgd;
+ pud_t *pud;
+ pmd_t *pmd;
+ pte_t *pte;
+
+ /*
+ * No early pte entries with !ARM64_64K_PAGES configuration, so using
+ * sections (pmd).
+ */
+ size = page64k ? PAGE_SIZE : SECTION_SIZE;
+ mask = ~(size - 1);
+
+ pgd = pgd_offset_k(virt);
+ pud = pud_offset(pgd, virt);
+ if (pud_none(*pud))
+ return NULL;
+ pmd = pmd_offset(pud, virt);
+
+ if (page64k) {
+ if (pmd_none(*pmd))
+ return NULL;
+ pte = pte_offset_kernel(pmd, virt);
+ set_pte(pte, __pte((phys & mask) | PROT_DEVICE_nGnRE));
+ } else {
+ set_pmd(pmd, __pmd((phys & mask) | PROT_SECT_DEVICE_nGnRE));
+ }
+
+ return (void __iomem *)((virt & mask) + (phys & ~mask));
+}
+#endif
+
static void __init map_mem(void)
{
struct memblock_region *reg;