irqchip: bcm7120-l2: Refactor driver for arbitrary IRQEN/IRQSTAT offsets

Currently the driver assumes that REG_BASE+0x00 is the IRQ enable mask,
and REG_BASE+0x04 is the IRQ status mask.  This is true on BCM3384 and
BCM7xxx, but it is not true for some of the controllers found on BCM63xx
chips.  So we will change a couple of key assumptions:

 - Don't assume that both the IRQEN and IRQSTAT registers will be
   covered by a single ioremap() operation.

 - Don't assume any particular ordering (IRQSTAT might show up before
   IRQEN on some chips).

 - For an L2 controller with >=64 IRQs, don't assume that every
   IRQEN/IRQSTAT pair will use the same register spacing.

This patch changes the "plumbing" but doesn't yet provide a way for users
to instantiate a controller with arbitrary IRQEN/IRQSTAT offsets.

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
irqchip: bcm7120-l2: Split STB-specific logic into its own function

The BCM7xxx instances of this block (listed in the register manual as
simply "IRQ0") all have the following items in common:

 - brcm,int-map-mask: for routing different bits in the L2 to different
   parent IRQs

 - brcm,int-fwd-mask: for hardwiring certain IRQs to bypass the L2 and
   use dedicated L1 lines

 - one enable/status pair (32 bits only)

Much of the driver code can be shared with BCM3380-style controllers, but
in order to do this cleanly, let's split out the BCM7xxx-specific logic
first.

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
irqchip: bcm7120-l2: Add support for BCM3380-style controllers

These controllers support multiple enable/status pairs (64+ IRQs),
can put the enable/status words at different offsets, and do not
support multiple parent IRQs.

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
irqchip: Add new driver for BCM7038-style level 1 interrupt controllers

This is the main peripheral IRQ controller on the BCM7xxx MIPS chips;
it has the following characteristics:

 - 64 to 160+ level IRQs
 - Atomic set/clear registers
 - Reasonably predictable register layout (N status words, then N
   mask status words, then N mask set words, then N mask clear words)
 - SMP affinity supported on most systems
 - Typically connected to MIPS IRQ 2,3,2,3 on CPUs 0,1,2,3

This driver registers one IRQ domain and one IRQ chip to cover all
instances of the block.  Up to 4 instances of the block may appear, as
it supports 4-way IRQ affinity on BCM7435.

The same block exists on the ARM BCM7xxx chips, but typically the ARM GIC
is used instead.  So this driver is primarily intended for MIPS STB chips.

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
MIPS: Let __dt_register_buses accept a single bus type

Some machines only have one bus type to register (e.g. "simple-bus").

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
MIPS: Fall back to the generic restart notifier

If the machine doesn't set its own _machine_restart callback, call the
common do_kernel_restart() instead.  This allows arch-independent reset
drivers from drivers/power/reset/ to be used to reboot the machine.

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
MIPS: Reorder MIPS_L1_CACHE_SHIFT priorities

Enabling support for more than one BMIPS CPU in the same build may
result in different L1_CACHE_SHIFT values, e.g.

    CPU_BMIPS5000 selects MIPS_L1_CACHE_SHIFT_7
    CPU_BMIPS4380 selects MIPS_L1_CACHE_SHIFT_6
    anything else defaults to MIPS_L1_CACHE_SHIFT_5

Ensure that if more than one MIPS_L1_CACHE_SHIFT_x option is selected,
Kconfig sets CONFIG_MIPS_L1_CACHE_SHIFT to the highest value.

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
MIPS: Create a common <asm/mach-generic/war.h>

11 platforms require at least one of these workarounds to be enabled; 22
platforms do not.  In the latter case we can fall back to a generic version.

Note that this also deletes an orphaned reference to RM9000_CDEX_SMP_WAR.

Suggested-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
MIPS: BMIPS: Flush the readahead cache after DMA

BMIPS 3300/435x/438x CPUs have a readahead cache that is separate from
the L1/L2.  During a DMA operation, accesses adjacent to a DMA buffer
may cause parts of the DMA buffer to be prefetched into the RAC.  To
avoid possible coherency problems, flush the RAC upon DMA completion.

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
MIPS: BMIPS: Document the firmware->kernel DTB interface

Add a new section covering the Generic BMIPS machine type.

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
MIPS: Add Generic BMIPS target

bmips_be_defconfig supports Linux running on the following CM and DSL
SoCs:

 - BCM3384 (BMIPS5000) cable modem application processor, BE, SMP
 - BCM3384 (BMIPS4355) cable modem "spare CPU"*, BE
 - BCM6328 (BMIPS4355) ADSL chip, BE
 - BCM6368 (BMIPS4350) ADSL chip, BE, SMP

*experimental; most configurations will require changing CONFIG_PHYSICAL_START

bmips_stb_defconfig supports Linux running on the (nominally LE) STB
chipsets:

 - BCM7125 (BMIPS4380) set-top box chip, LE, SMP
 - BCM7346 (BMIPS5000) set-top box chip, LE, SMP
 - BCM7360 (BMIPS3300) set-top box chip, LE
 - BCM7420 (BMIPS5000) set-top box chip, LE, SMP
 - BCM7425 (BMIPS5000) set-top box chip, LE, SMP

serial8250 and bcm63xx_uart do not currently coexist.  If/when this is
fixed, it will be also possible to boot the BE image on any supported STB
board configured for BE.  For now, each defconfig can only pick one UART
driver, and the BE defconfig enables bcm63xx_uart.

On these MIPS systems, endianness cannot be reconfigured at runtime.  On
STB it is sometimes offered as a board jumper or 0-ohm resistor, and
sometimes hardwired to LE only.  The CM and DSL systems always run BE.

Device Tree is used to configure the following items:

 - UART, USB, GENET peripherals
 - IRQ controllers
 - Early console base address (bcm63xx_uart only)
 - SMP or UP mode
 - MIPS counter frequency
 - Memory size / regions
 - DMA remappings
 - Reboot sequences
 - GISB bus error catcher
 - Kernel command line

The DT-enabled bootloader and build instructions for 3384 are posted at
https://github.com/Broadcom/aeolus .

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
MIPS: BMIPS: Add DTS files for several platforms

Most of the supported chips use legacy (non-DT) bootloaders, so they will
need to select an appropriate builtin DTB at compile time until the
bootloader is updated.  Provide suitable DTS files, and a means to compile
one of them into the kernel image.

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>