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At early time, the CPU CA73 retention state has been supported on
Hikey960.  Later we found the system has the hang issue and for
resolving this issue Hisilicon released new MCU firmware, but
unfortunately the new MCU firmware has side effect and results in the
CA73 CPU cannot really enter retention state and roll back to WFI state.

After discussion we cannot see the possibility to enable CA73 retention
state anymore on Hikey960, based on this conclusion we should remove
this state supporting from ARM-TF and roll back to WFI state only.  We
will commit one patch to remove CA73 CPU retention state in kernel DT
binding as well.

Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Haojian Zhuang <haojian.zhuang@linaro.org>
Cc: Kevin Wang <jean.wangtao@linaro.org>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Leo Yan <leo.yan@linaro.org>

This reverts commit fdae60b6.

The commit fdae60b6

 changed the
parameter encoding for the hikey960.  However that implies a DT change
in the kernel side.  After submitting the DT change for upstreaming,
the backward compatibility issue and the interface change raise some
concerns from the Linux community about the issues related to kernel <->
ATF alignment.  There is no way to detect a mis-alignment of those
without a deep knowledge of the ATF and the kernel.  Furthermore, the
failing calls to PSCI in the idle path (because of bad parameters), will
lead to busy looping, implying: thermal issues and extra energy
consumption.

In regard of the Linux community concerns, the potential issues when the
ATF and the kernel are not aligned, it is preferable to revert the
commit.

Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Haojian Zhuang <haojian.zhuang@linaro.org>
Cc: Kevin Wang <jean.wangtao@linaro.org>
Co-authored-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Leo Yan <leo.yan@linaro.org>

ARM Power State Coordination Interface (ARM DEN 0022D) chapter
6.5 "Recommended StateID Encoding" defines the state ID which can be
used by platforms. The recommended power states can be presented by
below values; and it divides into three fields, every field has 4 bits
to present power states corresponding to core level, cluster level and
system level.

  0: Run
  1: Standby
  2: Retention
  3: Powerdown

This commit changes to use upper recommended power states definition on
Hikey960; and changes the power state validate function to check the
power state passed from kernel side.
Signed-off-by: Leo Yan <leo.yan@linaro.org>

Clear the cpuidle flag when resuming from idle. This flag is set
when entering idle, and if it remains set when resuming, it can
prevent the cluster from powering off during the next system
suspend operation. During system suspend, all CPUs are plugged
out except the last CPU, which is suspended. If any of the
cpuidle flags are set at this point, the last CPU will be stuck
in a WFI loop and will not be powered off.
This problem only occurs during system suspend.
Signed-off-by: Tao Wang <kevin.wangtao@linaro.org>

In CPU off callback function, the old code uses the function
hisi_test_pwrdn_allcores() to check if all CPUs in cluster have been
powered off and if it's valid then power off the whole cluster. But the
function hisi_test_pwrdn_allcores() only maintains the different power
states only for CPU suspend/resume flow, so it cannot return correct
states for CPU on/off flow.

This patch is to change use hisi_test_cpu_down() to check if all CPUs
have been powered off, so that can power off the whole cluster properly
when all CPUs in cluster have been hotplugged off.
Signed-off-by: Tao Wang <kevin.wangtao@hisilicon.com>
Signed-off-by: Leo Yan <leo.yan@linaro.org>

Support BL31 on HiKey960 platform. Implement PSCI.
Signed-off-by: Leo Yan <leo.yan@linaro.org>
Signed-off-by: Haojian Zhuang <haojian.zhuang@linaro.org>