According to VLI64 Intel Atom E3800 Specification Update (#329901) concurrent read accesses may result in returning 0xffffffff and write accesses may be dropped silently. To workaround all accesses must be protected by locks. Cc: stable@vger.kernel.org Signed-off-by: Alexander Stein <alexander.stein@systec-electronic.com> Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>