arm64: add early_ioremap support

Add support for early IO or memory mappings which are needed before the
normal ioremap() is usable.  This also adds fixmap support for permanent
fixed mappings such as that used by the earlyprintk device register
region.

Signed-off-by: Mark Salter <msalter@redhat.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Borislav Petkov <borislav.petkov@amd.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 6 deletions

diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 61035d6814cb..1fe5d8d2bdfd 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -404,7 +404,7 @@ ENDPROC(__calc_phys_offset)
  *   - identity mapping to enable the MMU (low address, TTBR0)
  *   - first few MB of the kernel linear mapping to jump to once the MMU has
  *     been enabled, including the FDT blob (TTBR1)
- *   - UART mapping if CONFIG_EARLY_PRINTK is enabled (TTBR1)
+ *   - pgd entry for fixed mappings (TTBR1)
  */
 __create_page_tables:
         pgtbl   x25, x26, x24                   // idmap_pg_dir and swapper_pg_dir addresses
@@ -461,15 +461,12 @@ __create_page_tables:
         sub     x6, x6, #1                      // inclusive range
         create_block_map x0, x7, x3, x5, x6
 1:
-#ifdef CONFIG_EARLY_PRINTK
         /*
-         * Create the pgd entry for the UART mapping. The full mapping is done
-         * later based earlyprintk kernel parameter.
+         * Create the pgd entry for the fixed mappings.
          */
-        ldr     x5, =EARLYCON_IOBASE            // UART virtual address
+        ldr     x5, =FIXADDR_TOP                // Fixed mapping virtual address
         add     x0, x26, #2 * PAGE_SIZE         // section table address
         create_pgd_entry x26, x0, x5, x6, x7
-#endif
         ret
 ENDPROC(__create_page_tables)
         .ltorg