Re: [PATCH, RFC 0/8] ARM: AM43 (OMAP2+) boot support

From: Santosh Shilimkar
Date: Tue Feb 19 2013 - 05:08:48 EST

On Monday 18 February 2013 05:05 PM, Afzal Mohammed wrote:
(Resending, since it seems, LAKML doesn't accept patches with subject
prefix only as "RFC", but requires "PATCH" prefix also)


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.

After looking at the specs, you don't need the SMP mode since ACP
isn't being used.

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

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.

TWD use for AM437x is also limited because these times stops in
low power sates and there you will need broad-cast mechanism which
again more of SMP machine feature.

So I suggest to use the wakeup timer(GPT1) clock-event instead
of local timer for the mentioned reason.


To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at