-platform API is retired and instead callbacks are used
Signed-off-by: NVineet Gupta <vgupta@synopsys.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Acked-by: NArnd Bergmann <arnd@arndb.de>

The orig platform code orgnaization was singleton design pattern - only
one platform (and board thereof) would build at a time.

Thus any platform/board specific code (e.g. irq init, early init ...)
expected by ARC common code was exported as well defined set of APIs,
with only ONE instance building ever.

Now with multiple-platform build requirement, that design of code no
longer holds - multiple board specific calls need to build at the same
time - so ARC common code can't use the API approach, it needs a
callback based design where each board registers it's specific set of
functions, and at runtime, depending on board detection, the callbacks
are used from the registry.

This commit adds all the infrastructure, where board specific callbacks
are specified as a "maThine description".

All the hooks are placed in right spots, no board callbacks registered
yet (with MACHINE_STARt/END constructs) so the hooks will not run.

Next commit will actually convert the platform to this infrastructure.
Signed-off-by: NVineet Gupta <vgupta@synopsys.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Acked-by: NArnd Bergmann <arnd@arndb.de>

ARC common code to enable a SMP system + ISS provided SMP extensions.

ARC700 natively lacks SMP support, hence some of the core features are
are only enabled if SoCs have the necessary h/w pixie-dust. This
includes:
-Inter Processor Interrupts (IPI)
-Cache coherency
-load-locked/store-conditional
...

The low level exception handling would be completely broken in SMP
because we don't have hardware assisted stack switching. Thus a fair bit
of this code is repurposing the MMU_SCRATCH reg for event handler
prologues to keep them re-entrant.

Many thanks to Rajeshwar Ranga for his initial "major" contributions to
SMP Port (back in 2008), and to Noam Camus and Gilad Ben-Yossef for help
with resurrecting that in 3.2 kernel (2012).

Note that this platform code is again singleton design pattern - so
multiple SMP platforms won't build at the moment - this deficiency is
addressed in subsequent patches within this series.
Signed-off-by: NVineet Gupta <vgupta@synopsys.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Rajeshwar Ranga <rajeshwar.ranga@gmail.com>
Cc: Noam Camus <noamc@ezchip.com>
Cc: Gilad Ben-Yossef <gilad@benyossef.com>

There is a bit of hack/kludge right now where we disable preemption if a
L2 (High prio) IRQ is taken while L1 (Low prio) is active.

Need to revisit this
Signed-off-by: NVineet Gupta <vgupta@synopsys.com>

* arc-uart platform device now populated dynamically, using
  of_platform_populate() - applies to any other device whatsoever.

* uart in turn requires incore arc-intc to be also present in DT

* A irq-domain needs to be instantiated for IRQ requests by DT probed
  device (e.g. arc-uart)

TODO: switch over to linear irq domain once all devs have been
      transitioned to DT
Signed-off-by: NVineet Gupta <vgupta@synopsys.com>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: Arnd Bergmann <arnd@arndb.de>

This contains:
-bootup arch IRQ init: init_IRQ(), arc_init_IRQ()
-generic IRQ subsystem glue: arch_do_IRQ()
-basic IRQ chip setup for in-core intc
Signed-off-by: NVineet Gupta <vgupta@synopsys.com>
Cc: Thomas Gleixner <tglx@linutronix.de>

ARC700 has an in-core intc which provides 2 priorities (a.k.a.) "levels"
of interrupts (per IRQ) hencforth referred to as L1/L2 interrupts.

CPU flags register STATUS32 has Interrupt Enable bits per level (E1/E2)
to globally enable (or disable) all IRQs at a level. Hence the
implementation of arch_local_irq_{save,restore,enable,disable}( )

The STATUS32 reg can be r/w only using the AUX Interface of ARC, hence
the use of LR/SR instructions. Further, E1/E2 bits in there can only be
updated using the FLAG insn.

The intc supports 32 interrupts - and per IRQ enabling is controlled by
a bit in the AUX_IENABLE register, hence the implmentation of
arch_{,un}mask_irq( ) routines.
Signed-off-by: NVineet Gupta <vgupta@synopsys.com>
Cc: Thomas Gleixner <tglx@linutronix.de>