ARM: 7980/1: kernel: improve error message when LPAE config doesn't match CPU

Currently, when the kernel is configured with LPAE support, but the
CPU doesn't support it, the error message is fairly cryptic:

  Error: unrecognized/unsupported processor variant (0x561f5811).

This messages is normally shown when there is an issue when comparing
the processor ID (CP15 0, c0, c0) with the values/masks described in
proc-v7.S. However, the same message is displayed when LPAE support is
enabled in the kernel configuration, but not available in the CPU,
after looking at ID_MMFR0 (CP15 0, c0, c1, 4). Having the same error
message is highly misleading.

This commit improves this by showing a different error message when
this situation occurs:

  Error: Kernel with LPAE support, but CPU does not support LPAE.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

2 files changed, 13 insertions, 1 deletions

diff --git a/arch/arm/kernel/head-common.S b/arch/arm/kernel/head-common.S
index 47cd974e57ea..c96ecacb2021 100644
--- a/arch/arm/kernel/head-common.S
+++ b/arch/arm/kernel/head-common.S
@@ -177,6 +177,18 @@ __lookup_processor_type_data:
         .long   __proc_info_end
         .size   __lookup_processor_type_data, . - __lookup_processor_type_data
 
+__error_lpae:
+#ifdef CONFIG_DEBUG_LL
+        adr     r0, str_lpae
+        bl      printascii
+        b       __error
+str_lpae: .asciz "\nError: Kernel with LPAE support, but CPU does not support LPAE.\n"
+#else
+        b       __error
+#endif
+        .align
+ENDPROC(__error_lpae)
+
 __error_p:
 #ifdef CONFIG_DEBUG_LL
         adr     r0, str_p1
diff --git a/arch/arm/kernel/head.S b/arch/arm/kernel/head.S
index 914616e0bdcd..f5f381d91556 100644
--- a/arch/arm/kernel/head.S
+++ b/arch/arm/kernel/head.S
@@ -102,7 +102,7 @@ ENTRY(stext)
         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
+        blo     __error_lpae                    @ only classic page table format
 #endif
 
 #ifndef CONFIG_XIP_KERNEL