ARM: 8452/3: PJ4: make coprocessor access sequences buildable in Thumb2 mode

Commit 5008efc83bf85b647aa1cbc44718b1675bbb7444 upstream.

The PJ4 inline asm sequence to write to cp15 cannot be built in Thumb-2
mode, due to the way it performs arithmetic on the program counter, so it
is built in ARM mode instead. However, building C files in ARM mode under
CONFIG_THUMB2_KERNEL is problematic, since the instrumentation performed
by subsystems like ftrace does not expect having to deal with interworking

Since the sequence in question is simply a poor man's ISB instruction,
let's use a straight 'isb' instead when building in Thumb2 mode. Thumb2
implies V7, so 'isb' should always be supported in that case.

Acked-by: Arnd Bergmann <>
Acked-by: Nicolas Pitre <>
Signed-off-by: Ard Biesheuvel <>
Signed-off-by: Russell King <>
Signed-off-by: Arnd Bergmann <>
2 files changed