xtensa: add alternative kernel memory layouts

MMUv3 is able to support low memory bigger than 128MB.
Implement 256MB and 512MB KSEG layouts:

- add Kconfig selector for KSEG layout;
- add KSEG base address, size and alignment definitions to
  arch/xtensa/include/asm/kmem_layout.h;
- use new definitions in TLB initialization;
- add build time memory map consistency checks.

See Documentation/xtensa/mmu.txt for the details of new memory layouts.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/arch/xtensa/include/asm/fixmap.h b/arch/xtensa/include/asm/fixmap.h
index 62b507deea9d..0d30403b6c95 100644
--- a/arch/xtensa/include/asm/fixmap.h
+++ b/arch/xtensa/include/asm/fixmap.h
@@ -59,6 +59,11 @@ enum fixed_addresses {
  */
 static __always_inline unsigned long fix_to_virt(const unsigned int idx)
 {
+	/* Check if this memory layout is broken because fixmap overlaps page
+	 * table.
+	 */
+	BUILD_BUG_ON(FIXADDR_START <
+		     XCHAL_PAGE_TABLE_VADDR + XCHAL_PAGE_TABLE_SIZE);
 	BUILD_BUG_ON(idx >= __end_of_fixed_addresses);
 	return __fix_to_virt(idx);
 }