ARM: Meson6: enable SMP
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Cover letter [PATCH 0/3] ARM: Meson6: enable SMP
Quoted 44 lines · Arnd Bergmann
Quoted 43 lines · On Thursday 02 October 2014 17:38:04 Maxime Ripard wrote:
Quoted 41 lines · Arnd Bergmann
Quoted 27 lines · On Thursday 02 October 2014 16:54:26 Maxime Ripard wrote:
Quoted 26 lines · Arnd Bergmann
Quoted 12 lines · On Tuesday 30 September 2014 22:45:38 Carlo Caione wrote:
Quoted 11 lines · Arnd Bergmann
Quoted 6 lines · On Tuesday 30 September 2014 10:46:46 Carlo Caione wrote:
Quoted 2 lines · Carlo Caione
Amlogic Meson6 is a dual-core Cortex-A9. This patchset adds all the necessary pieces to boot the secondary CPU.
Sorry for the double sending.
Forgot to CC LAKML.Looks good to me in principle, but I wonder about the CPU enable method. Are you able to implement PSCI in u-boot like it was done for allwinner?
Quoted 8 lines
Quoted 2 lines
This is mostly a question of whether the system comes up in secure mode or non-secure mode.
I would be able if I had the u-boot source code or the possibility to flash the board I'm using. Unfortunately at this moment I don't have either. Probably in the near future I'll be able to implement PSCI in u-boot since Amlogic is kindly starting to provide documentation but now this is the best I can do.
Ok, I see. Let's give Amlogic some more time then. I think it's better to merge other parts of the platform first when we can reasonably assume that we don't have to change the binding any more.
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Quoted 3 lines
It would be a shame to merge this now and then make it obsolete by implementing PSCI but still having to carry around the original code for compatibility reasons.
More likely, PSCI is not going to be supported by the bootloaders of the devices already in the wild, so we still have to provide them an option. And even when it will, you'll still have to support both the devices with the old bootloaders, and the one with the new.
It depends on how common the old boot loaders are, and whether it's possible to upgrade them. If we can get to the point where you can boot a kernel with a single CPU and have an easy way to update the boot loader, we don't need to support it.
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Quoted 5 lines
I thought I heard Olof at some point ranting about this kind of requirements, but ok
Still, holding off until something that hypothetical happens looks a bit odd, doesn't it?
I was mainly trying to follow what you are doing in mach-sunxi, but maybe I misunderstood what your plans are for PSCI support there.
Well, we did it only for the A20, because:
- We had a very good bootloader support already
- And we needed it to be able to use it for virtualization
AFAIK, the amlogic guys don't have such a bootloader yet, and can't use the virtualization, since it's a cortex-a9.
Note that for all the other SoCs, where we don't have such a bootloader support, we do have smp_ops, or will have, because we can just use Allwinner's bootloader.
Quoted 3 lines
mach-meson is still in a very early stage, and it's not like SMP support is the most important feature missing from it. If there are good reasons to include the current patches in 3.19, we can do that.
That's more of a mainlining scheduling discussion, and I can't really argue with that. I wouldn't have done it in that order, but I'm not really sure we can do that on that argument alone.
The only question that should matter I guess is whether this feature improves the overall support of the SoC, and whether the code is clean enough. If both answers are yes, then I think it should come in.
Remember that Carlo is a hobbyist, and doesn't really have an agenda :)
Maxime
Signature · 10 lines
Maxime Ripard, Free Electrons Embedded Linux, Kernel and Android engineering http://free-electrons.com -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 819 bytes Desc: Digital signature URL: <http://lists.infradead.org/pipermail/linux-arm-kernel/attachments/20141003/c7f25ef2/attachment.sig>