drivers/console: Link console framework code by default ...

This patch makes the build system link the console framework code by
default, like it already does with other common libraries (e.g. cache
helpers). This should not make a difference in practice since TF is
linked with --gc-sections, so the linker will garbage collect all
functions and data that are not referenced by any other code. Thus, if a
platform doesn't want to include console code for size reasons and
doesn't make any references to console functions, the code will not be
included in the final binary.

To avoid compatibility issues with older platform ports, only make this
change for the MULTI_CONSOLE_API.

Change-Id: I153a9dbe680d57aadb860d1c829759ba701130d3
Signed-off-by: Julius Werner <jwerner@chromium.org>

plat/common/crash_console_helpers.S: Fix MULTI_CONSOLE_API support ...

Crash reporting via the default consoles registered by MULTI_CONSOLE_API
has been broken since commit d35cc34 (Console: Use callee-saved
registers), which was introduced to allow console drivers written in C.
It's not really possible with the current crash reporting framework to
support console drivers in C, however we should make sure that the
existing assembly drivers that do support crash reporting continue to
work through the MULTI_CONSOLE_API.

This patch fixes the problem by creating custom console_putc() and
console_flush() implementations for the crash reporting case that do not
use the stack. Platforms that want to use this feature will have to link
plat/common/aarch64/crash_console_helpers.S explicitly.

Also update the documentation to better reflect the new reality (of this
being an option rather than the expected default for most platforms).

Change-Id: Id0c761e5e2fddaf25c277bc7b8ab603946ca73cb
Signed-off-by: Julius Werner <jwerner@chromium.org>

Console: Use callee-saved registers ...

This allows the console drivers to be implemented in C

Change-Id: Ibac859c4bcef0e92a0dcacc6b58ac19bc69b8342
Signed-off-by: Sathees Balya <sathees.balya@arm.com>

Ensure read and write of flags are 32 bit ...

In 'console_set_scope' and when registering a console, field 'flags' of
'console_t' is assigned a 32-bit value. However, when it is actually
used, the functions perform 64-bit reads to access its value. This patch
changes all 64-bit reads to 32-bit reads.

Change-Id: I181349371409e60065335f078857946fa3c32dc1
Signed-off-by: Daniel Boulby <daniel.boulby@arm.com>

multi console: Assert that consoles aren't registered twice ...

In the multi console driver, allowing to register the same console more
than once may result in an infinte loop when putc is called.

If, for example, a boot message is trying to be printed, but the
consoles in the loop in the linked list are runtime consoles, putc will
iterate forever looking for a console that can print boot messages (or
a NULL pointer that will never come).

This loop in the linked list can occur after restoring the system from a
system suspend. The boot console is registered during the cold boot in
BL31, but the runtime console is registered even in the warm boot path.
Consoles are always added to the start of the linked list when they are
registered, so this it what should happen if they were actually
different structures:

   console_list -> NULL
   console_list -> BOOT -> NULL
   console_list -> RUNTIME -> BOOT -> NULL
   console_list -> RUNTIME -> RUNTIME -> BOOT -> NULL

In practice, the two runtime consoles are the same one, so they create
this loop:

   console_list -> RUNTIME -.    X -> BOOT -> NULL
                       ^    |
                       `----'

This patch adds an assertion to detect this problem. The assertion will
fail whenever the same structure tries to be registered while being on
the list.

In order to assert this, console_is_registered() has been implemented.
It returns 1 if the specified console is registered, 0 if not.

Change-Id: I922485e743775ca9bd1af9cbd491ddd360526a6d
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

Add new function-pointer-based console API ...

This patch overhauls the console API to allow for multiple console
instances of different drivers that are active at the same time. Instead
of binding to well-known function names (like console_core_init),
consoles now provide a register function (e.g. console_16550_register())
that will hook them into the list of active consoles. All console
operations will be dispatched to all consoles currently in the list.

The new API will be selected by the build-time option MULTI_CONSOLE_API,
which defaults to ${ERROR_DEPRECATED} for now. The old console API code
will be retained to stay backwards-compatible to older platforms, but
should no longer be used for any newly added platforms and can hopefully
be removed at some point in the future.

The new console API is intended to be used for both normal (bootup) and
crash use cases, freeing platforms of the need to set up the crash
console separately. Consoles can be individually configured to be active
active at boot (until first handoff to EL2), at runtime (after first
handoff to EL2), and/or after a crash. Console drivers should set a sane
default upon registration that can be overridden with the
console_set_scope() call. Code to hook up the crash reporting mechanism
to this framework will be added with a later patch.

This patch only affects AArch64, but the new API could easily be ported
to AArch32 as well if desired.

Change-Id: I35c5aa2cb3f719cfddd15565eb13c7cde4162549
Signed-off-by: Julius Werner <jwerner@chromium.org>