C6X: devicetree support

This is the basic devicetree support for C6X. Currently, four boards are
supported. Each one uses a different SoC part. Two of the four supported
SoCs are multicore. One with 3 cores and the other with 6 cores. There is
no coherency between the core-level caches, so SMP is not an option. It is
possible to run separate kernel instances on the various cores. There is
currently no C6X bootloader support for device trees so we build in the DTB
for now.

There are some interesting twists to the hardware which are of note for device
tree support. Each core has its own interrupt controller which is controlled
by special purpose core registers. This core controller provides 12 general
purpose prioritized interrupt sources. Each core is contained within a
hardware "module" which provides L1 and L2 caches, power control, and another
interrupt controller which cascades into the core interrupt controller. These
core module functions are controlled by memory mapped registers. The addresses
for these registers are the same for each core. That is, when coreN accesses
a module-level MMIO register at a given address, it accesses the register for
coreN even though other cores would use the same address to access the register
in the module containing those cores. Other hardware modules (timers, enet, etc)
which are memory mapped can be accessed by all cores.

The timers need some further explanation for multicore SoCs. Even though all
timer control registers are visible to all cores, interrupt routing or other
considerations may make a given timer more suitable for use by a core than
some other timer. Because of this and the desire to have the same image run
on more than one core, the timer nodes have a "ti,core-mask" property which
is used by the driver to scan for a suitable timer to use.

Signed-off-by: Mark Salter <msalter@redhat.com>
Signed-off-by: Aurelien Jacquiot <a-jacquiot@ti.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>

1 files changed, 104 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/c6x/interrupt.txt b/Documentation/devicetree/bindings/c6x/interrupt.txt
new file mode 100644
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+C6X Interrupt Chips
+-------------------
+
+* C64X+ Core Interrupt Controller
+
+  The core interrupt controller provides 16 prioritized interrupts to the
+  C64X+ core. Priority 0 and 1 are used for reset and NMI respectively.
+  Priority 2 and 3 are reserved. Priority 4-15 are used for interrupt
+  sources coming from outside the core.
+
+  Required properties:
+  --------------------
+  - compatible: Should be "ti,c64x+core-pic";
+  - #interrupt-cells: <1>
+
+  Interrupt Specifier Definition
+  ------------------------------
+  Single cell specifying the core interrupt priority level (4-15) where
+  4 is highest priority and 15 is lowest priority.
+
+  Example
+  -------
+  core_pic: interrupt-controller@0 {
+	interrupt-controller;
+	#interrupt-cells = <1>;
+	compatible = "ti,c64x+core-pic";
+  };
+
+
+
+* C64x+ Megamodule Interrupt Controller
+
+  The megamodule PIC consists of four interrupt mupliplexers each of which
+  combine up to 32 interrupt inputs into a single interrupt output which
+  may be cascaded into the core interrupt controller. The megamodule PIC
+  has a total of 12 outputs cascading into the core interrupt controller.
+  One for each core interrupt priority level. In addition to the combined
+  interrupt sources, individual megamodule interrupts may be cascaded to
+  the core interrupt controller. When an individual interrupt is cascaded,
+  it is no longer handled through a megamodule interrupt combiner and is
+  considered to have the core interrupt controller as the parent.
+
+  Required properties:
+  --------------------
+  - compatible: "ti,c64x+megamod-pic"
+  - interrupt-controller
+  - #interrupt-cells: <1>
+  - reg: base address and size of register area
+  - interrupt-parent: must be core interrupt controller
+  - interrupts: This should have four cells; one for each interrupt combiner.
+                The cells contain the core priority interrupt to which the
+                corresponding combiner output is wired.
+
+  Optional properties:
+  --------------------
+  - ti,c64x+megamod-pic-mux: Array of 12 cells correspnding to the 12 core
+                             priority interrupts. The first cell corresponds to
+                             core priority 4 and the last cell corresponds to
+                             core priority 15. The value of each cell is the
+                             megamodule interrupt source which is MUXed to
+                             the core interrupt corresponding to the cell
+                             position. Allowed values are 4 - 127. Mapping for
+                             interrupts 0 - 3 (combined interrupt sources) are
+                             ignored.
+
+  Interrupt Specifier Definition
+  ------------------------------
+  Single cell specifying the megamodule interrupt source (4-127). Note that
+  interrupts mapped directly to the core with "ti,c64x+megamod-pic-mux" will
+  use the core interrupt controller as their parent and the specifier will
+  be the core priority level, not the megamodule interrupt number.
+
+  Examples
+  --------
+  megamod_pic: interrupt-controller@1800000 {
+	compatible = "ti,c64x+megamod-pic";
+	interrupt-controller;
+	#interrupt-cells = <1>;
+	reg = <0x1800000 0x1000>;
+	interrupt-parent = <&core_pic>;
+	interrupts = < 12 13 14 15 >;
+  };
+
+  This is a minimal example where all individual interrupts go through a
+  combiner. Combiner-0 is mapped to core interrupt 12, combiner-1 is mapped
+  to interrupt 13, etc.
+
+
+  megamod_pic: interrupt-controller@1800000 {
+	compatible = "ti,c64x+megamod-pic";
+	interrupt-controller;
+	#interrupt-cells = <1>;
+	reg = <0x1800000 0x1000>;
+	interrupt-parent = <&core_pic>;
+	interrupts = < 12 13 14 15 >;
+	ti,c64x+megamod-pic-mux = <  0  0  0  0
+                                    32  0  0  0
+                                     0  0  0  0 >;
+  };
+
+  This the same as the first example except that megamodule interrupt 32 is
+  mapped directly to core priority interrupt 8. The node using this interrupt
+  must set the core controller as its interrupt parent and use 8 in the
+  interrupt specifier value.