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At present, the build option TSP_NS_INTR_ASYNC_PREEMPT controls how
Non-secure interrupt affects TSPs execution. When TSP is executing:

  1. When TSP_NS_INTR_ASYNC_PREEMPT=0, Non-secure interrupts are received
     at the TSP's exception vector, and TSP voluntarily preempts itself.

  2. When TSP_NS_INTR_ASYNC_PREEMPT=1, Non-secure interrupts causes a
     trap to EL3, which preempts TSP execution.

When EL3 exception handling is in place (i.e.,
EL3_EXCEPTION_HANDLING=1), FIQs are always trapped to EL3. On a system
with GICv3, pending NS interrupts while TSP is executing will be
signalled as FIQ (which traps to EL3). This situation necessitates the
same treatment applied to case (2) above.

Therefore, when EL3 exception handling is in place, additionally
require that TSP_NS_INTR_ASYNC_PREEMPT is set to one 1.

Strictly speaking, this is not required on a system with GICv2, but the
same model is uniformly followed regardless, for simplicity.

Relevant documentation updated.

Change-Id: I928a8ed081fb0ac96e8b1dfe9375c98384da1ccd
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>

When ARM Trusted Firmware is built with EL3_EXCEPTION_HANDLING=1,
EL3 interrupts (INTR_TYPE_EL3) will always preempt both Non-secure and
secure execution.

The interrupt management framework currently treats EL3 interrupt
routing as valid. For the above reason, this patch makes them invalid
when EL3_EXCEPTION_HANDLING is in effect.

Change-Id: I95bca8f5dc8df8eb0ff6f305cfba098611522a39
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>

Due to recent issues in the rendering of the documentation on GitHub and
some long-standing issues like the lack of automatic table of content in
Markdown, the documentation has been converted to reStructuredText.
Basic constructs looks pretty similar to Markdown.

Automatically convert GitHub markdown documentation to reStructuredText
using pandoc.

Change-Id: If20b695acedc6d1b49c8d9fb64efd6b6ba23f4a9
Signed-off-by: Douglas Raillard <douglas.raillard@arm.com>