powerpc/85xx: verify the current address of CCSR before relocating it

Verify that CCSR is actually located where it is supposed to be before
we relocate it.  This is useful in detecting U-Boot configurations that
are broken (e.g. an incorrect value for CONFIG_SYS_CCSRBAR_DEFAULT).
If the current value is wrong, we enter an infinite loop, which is handy
for debuggers.

Signed-off-by: Timur Tabi <timur@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>

diff --git a/arch/powerpc/cpu/mpc85xx/start.S b/arch/powerpc/cpu/mpc85xx/start.S
index e519f35..d494528 100644 (file)
--- a/arch/powerpc/cpu/mpc85xx/start.S
+++ b/arch/powerpc/cpu/mpc85xx/start.S
@@ -411,6 +411,33 @@ create_ccsr_old_tlb:
        msync
        tlbwe
 
+       /*
+        * We have a TLB for what we think is the current (old) CCSR.  Let's
+        * verify that, otherwise we won't be able to move it.
+        * CONFIG_SYS_CCSRBAR_DEFAULT is always a 32-bit number, so we only
+        * need to compare the lower 32 bits of CCSRBAR on CoreNet systems.
+        */
+verify_old_ccsr:
+       lis     r0, CONFIG_SYS_CCSRBAR_DEFAULT@h
+       ori     r0, r0, CONFIG_SYS_CCSRBAR_DEFAULT@l
+#ifdef CONFIG_FSL_CORENET
+       lwz     r1, 4(r9)               /* CCSRBARL */
+#else
+       lwz     r1, 0(r9)               /* CCSRBAR, shifted right by 12 */
+       slwi    r1, r1, 12
+#endif
+
+       cmpl    0, r0, r1
+
+       /*
+        * If the value we read from CCSRBARL is not what we expect, then
+        * enter an infinite loop.  This will at least allow a debugger to
+        * halt execution and examine TLBs, etc.  There's no point in going
+        * on.
+        */
+infinite_debug_loop:
+       bne     infinite_debug_loop
+
 #ifdef CONFIG_FSL_CORENET
 
 #define CCSR_LAWBARH0  (CONFIG_SYS_CCSRBAR + 0x1000)