RFC ARM: AM43 (OMAP2+) boot support

(Resending, since it seems, LAKML doesn't accept patches with subject prefix only as "RFC", but requires "PATCH" prefix also)

Hi,

This series adds minimal support to boot Linux on platforms having AM43 based SoC's.

This is being sent as an RFC to seek opinion about modification in twd to register percpu local timer clock event for scheduler tick in the case of one core SMP.

AM43 SoC's are based on ARM Cortex-A9. It is an ARM Cortex-A9 SMP configuration with one core (not uniprocessor configuration). AM43 is similar to AM335x in it's peripheral capabilities, with many of the peripheral register mapping's similar like that of uart.

AM43 is in pre-silicon stage and currently there are no public documents.

This series has been tested on a pre-silicon platform that emulates AM43 SoC, changes proposed here are minimal - to get it booting. Kernel was directly run without the help of bootloader - Images were directly loaded onto a pre-initialized RAM and ARM registers updated as required for booting.

Changes have been made over linux-next (next-20130213) with three "OF" related reverts (which otherwise causes problem in other platforms also) and compiled with omap2plus_defconfig. Multiplatform option was enabled, while most of CONFIG options were deselected for a faster boot. Beagle bone boots as earlier with these changes.

An interesting observation is that it may be possible to boot this platform to console without any platform specific modification to proper Kernel (by that I mean excluding DT sources) using Arnd's,

"[PATCH,RFC] default machine descriptor for multiplatform",

along with a "CLOCKSOURCE_OF_DECLARE" for smp twd.

But later on to make SoC do any really useful work or to get done things that the SoC is meant to do, platform changes like omap-hwmod, handling power management, clock tree, detecting SoC capabilities etc would have to be made, necessitating DT_MACHINE_START at least in the foreseeable future.

Patch - 8 that makes AM43 boot on pre-silicon platform would be replaced later by a one for original board.

Last but not least, thanks to Ankur Kishore <[email protected]> (who first made Linux to boot on AM43) for all the help that made Linux bringup easier.

Regards
Afzal

Afzal Mohammed (8):
ARM: localtimer: return percpu clkevt on register
ARM: twd: register clock event for 1 core SMP
ARM: twd: clock rate from DT (if no DT clk tree)
ARM: am33xx: ll debug config help
ARM: OMAP2+: am43: Kconfig
ARM: OMAP2+: am43: basic dt support
ARM: dts: am4372: initial support
ARM: dts: am43-pre-silicon support

 Documentation/devicetree/bindings/arm/twd.txt |  7 +++-
 arch/arm/Kconfig.debug                        |  3 ++
 arch/arm/boot/dts/Makefile                    |  3 +-
 arch/arm/boot/dts/am43-pre-silicon.dts        | 31 +++++++++++++++
 arch/arm/boot/dts/am4372.dtsi                 | 55 +++++++++++++++++++++++++++
 arch/arm/include/asm/localtimer.h             |  7 ++--
 arch/arm/kernel/smp.c                         |  8 ++--
 arch/arm/kernel/smp_twd.c                     | 16 +++++++-
 arch/arm/mach-omap2/Kconfig                   | 11 ++++++
 arch/arm/mach-omap2/board-generic.c           | 18 +++++++++
 10 files changed, 148 insertions(+), 11 deletions(-)
 create mode 100644 arch/arm/boot/dts/am43-pre-silicon.dts
 create mode 100644 arch/arm/boot/dts/am4372.dtsi

1.7.12