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Various CPU drivers in ARM Trusted Firmware register functions to handle
power-down operations. At present, separate functions are registered to
power down individual cores and clusters.

This scheme operates on the basis of core and cluster, and doesn't cater
for extending the hierarchy for power-down operations. For example,
future CPUs might support multiple threads which might need powering
down individually.

This patch therefore reworks the CPU operations framework to allow for
registering power down handlers on specific level basis. Henceforth:

  - Generic code invokes CPU power down operations by the level
    required.

  - CPU drivers explicitly mention CPU_NO_RESET_FUNC when the CPU has no
    reset function.

  - CPU drivers register power down handlers as a list: a mandatory
    handler for level 0, and optional handlers for higher levels.

All existing CPU drivers are adapted to the new CPU operations framework
without needing any functional changes within.

Also update firmware design guide.

Change-Id: I1826842d37a9e60a9e85fdcee7b4b8f6bc1ad043
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>

The AArch32 Procedure call Standard mandates that the stack must be aligned
to 8 byte boundary at external interfaces. This patch does the required
changes.

This problem was detected when a crash was encountered in
`psci_print_power_domain_map()` while printing 64 bit values. Aligning
the stack to 8 byte boundary resolved the problem.

Fixes ARM-Software/tf-issues#437

Change-Id: I517bd8203601bb88e9311bd36d477fb7b3efb292
Signed-off-by: Soby Mathew <soby.mathew@arm.com>

There are many instances in ARM Trusted Firmware where control is
transferred to functions from which return isn't expected. Such jumps
are made using 'bl' instruction to provide the callee with the location
from which it was jumped to. Additionally, debuggers infer the caller by
examining where 'lr' register points to. If a 'bl' of the nature
described above falls at the end of an assembly function, 'lr' will be
left pointing to a location outside of the function range. This misleads
the debugger back trace.

This patch defines a 'no_ret' macro to be used when jumping to functions
from which return isn't expected. The macro ensures to use 'bl'
instruction for the jump, and also, for debug builds, places a 'nop'
instruction immediately thereafter (unless instructed otherwise) so as
to leave 'lr' pointing within the function range.

Change-Id: Ib34c69fc09197cfd57bc06e147cc8252910e01b0
Co-authored-by: Douglas Raillard <douglas.raillard@arm.com>
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>

This patch adds AArch32 support to PSCI library, as follows :

* The `psci_helpers.S` is implemented for AArch32.

* AArch32 version of internal helper function `psci_get_ns_ep_info()` is
  defined.

* The PSCI Library is responsible for the Non Secure context initialization.
  Hence a library interface `psci_prepare_next_non_secure_ctx()` is introduced
  to enable EL3 runtime firmware to initialize the non secure context without
  invoking context management library APIs.

Change-Id: I25595b0cc2dbfdf39dbf7c589b875cba33317b9d