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During system suspend, the GICv3 Distributor and Redistributor context
can be lost due to power gating of the system power domain. This means
that the GICv3 context needs to be saved prior to system suspend and
restored on wakeup. Currently the consensus is that the Firmware should
be in charge of this. See tf-issues#464 for more details.

This patch introduces helper APIs in the GICv3 driver to save and
restore the Distributor and Redistributor contexts. The GICv3 ITS
context is not considered in this patch because the specification says
that the details of ITS power management is implementation-defined.
These APIs are expected to be appropriately invoked by the platform
layer during system suspend.

Fixes ARM-software/tf-issues#464

Change-Id: Iebb9c6770ab8c4d522546f161fa402d2fe02ec00
Signed-off-by: Soby Mathew <soby.mathew@arm.com>
Signed-off-by: Douglas Raillard <douglas.raillard@arm.com>

Reindent the file using tabs as the mix of spaces and tabs confuses some
editors and leads them to use spaces instead of tabs for new code
although the coding style mandates tabs.

Change-Id: I87fa4a5d368a048340054b9b3622325f3f7befba
Signed-off-by: Douglas Raillard <douglas.raillard@arm.com>

ARM GIC-600 IP complies with ARM GICv3 architecture, but among others,
implements a power control register in the Redistributor frame. This
register must be programmed to mark the frame as powered on, before
accessing other registers in the frame. Rest of initialization sequence
remains the same.

The driver provides APIs for Redistributor power management, and
overrides those in the generic GICv3 driver. The driver data is shared
between generic GICv3 driver and that of GIC-600.

For FVP platform, the GIC-600 driver is chosen when FVP_USE_GIC_DRIVER
is set to FVP_GIC600. Also update user guide.

Change-Id: I321b2360728d69f6d4b0a747b2cfcc3fe5a20d67
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>