Messages in this thread | | | Date | Mon, 31 Oct 2016 08:18:27 +0000 | From | Russell King - ARM Linux <> | Subject | Re: [PATCH 1/2] ARM: oxnas: Add OX820 SMP support |
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On Mon, Oct 17, 2016 at 11:34:32AM +0200, Neil Armstrong wrote: > On 10/17/2016 11:06 AM, Arnd Bergmann wrote: > > On Monday, October 17, 2016 10:43:02 AM CEST Neil Armstrong wrote: > > This seems to have been copied from plat-versatile, but is really > > not needed here since you apparently have proper hardware support for > > starting up the CPUs. > Yes it seems. > > > > > Any reason you can't just write to the cpu_ctrl register > > once and keep going without that whole holding_pen loop > > and spinlock? > I suppose but I did not find any good examples except the plat-versatile code. > I will try some simpler code.
There's plenty of examples - most ARM SMP platforms in the kernel now do not blindly copy the versatile code. You only have to go looking for arch/arm/*/platsmp.c files to find them.
I'm not sure what you'd call a "good example" - maybe the imx code? arch/arm/mach-imx/platsmp.c can't be simpler:
static int imx_boot_secondary(unsigned int cpu, struct task_struct *idle) { imx_set_cpu_jump(cpu, v7_secondary_startup); imx_enable_cpu(cpu, true); return 0; }
I guess the difficult thing is to understand what each of those called functions does... though the function names give a very accurate clue there.
and because plat-versatile is almost entirely software-based, it's easy to understand and follow, _despite_ being completely broken for things like PM and kexec (which, the platform does not support.)
-- RMK's Patch system: http://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up according to speedtest.net.
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