ARM: 7275/1: LPAE: Check the CPU support for the long descriptor format

This patch adds a check for the presence of the LPAE feature during the
CPU initialisation. If not present, it reports an error when
CONFIG_DEBUG_LL is enabled.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 8 insertions, 0 deletions

diff --git a/arch/arm/kernel/head.S b/arch/arm/kernel/head.S
index 14e277d2ff9..6d579114406 100644
--- a/arch/arm/kernel/head.S
+++ b/arch/arm/kernel/head.S
@@ -99,6 +99,14 @@ ENTRY(stext)
  THUMB( it      eq )            @ force fixup-able long branch encoding
         beq     __error_p                       @ yes, error 'p'
 
+#ifdef CONFIG_ARM_LPAE
+        mrc     p15, 0, r3, c0, c1, 4           @ read ID_MMFR0
+        and     r3, r3, #0xf                    @ extract VMSA support
+        cmp     r3, #5                          @ long-descriptor translation table format?
+ THUMB( it      lo )                            @ force fixup-able long branch encoding
+        blo     __error_p                       @ only classic page table format
+#endif
+
 #ifndef CONFIG_XIP_KERNEL
         adr     r3, 2f
         ldmia   r3, {r4, r8}