Hi Andre,
2016-06-19 19:33 GMT+09:00 André Przywara <andre.przyw...@arm.com>: > Hi, > > On 19/06/16 09:57, Masahiro Yamada wrote: >> 2016-06-18 18:40 GMT+09:00 Linus Walleij <linus.wall...@linaro.org>: >>> On Fri, Jun 17, 2016 at 2:51 PM, Masahiro Yamada >>> <yamada.masah...@socionext.com> wrote: >>> >>>> There are two enable methods supported by ARM64 Linux; psci and >>>> spin-table. The latter is simpler and easier to use for quick SoC >>>> bring-up. >>>> >>>> So, I used the spin-table for my first ARMv8 SoC porting, but I >>>> found its support in U-Boot was poor. It is true there exists a >>>> code fragment for the spin code in arch/arm/cpu/armv8/start.S, >>>> but I see some problems: >>> >>> Is part of the motivation for this approach to boot an ARMv8 system >>> without using the ARM Trusted Firmware? >>> >>> Yours, >>> Linus Walleij >> >> Yes, exactly. >> >> It would be the best choice >> to switch over to PSCI with ATF in a long run, >> but, I decided to use spin-table for the initial SoC bring-up >> because of tight schedule. > > So if you don't have an ATF port ready, why not use U-Boot's PSCI > implementation meanwhile? I think there are efforts underway to make > PSCI enablement for random new boards a walk in the park (by making the > PSCI support as generic as possible, CCing Chen-Yu for this). So, you mean U-Boot can serve PSCI for ARMv8 SoCs without ATF, right? (and efforts underway for further improvement) I know PSCI support is available for ARMv7 (arch/arm/cpu/armv7/psci.S), but I could not find PSCI implementation in arch/arm/cpu/armv8/ directory in the mainline U-Boot. I checked Chen-Yu's patches on Patchwork, but I think they are mostly for improvement of ARMv7 PSCI support. If I am missing something, could you point me to the reference, please? > IIRC the spin-table boot method was just introduced to cope with cores > that don't have EL3 and thus cannot provide PSCI services the normal way > (and that don't want to or cannot sacrifice EL2 for that). > So I am a bit wary of proliferating this SMP method. Proliferating? Many of ARM 32bit SoCs have vendor-specific SMP methods. On the other hand, ARM64 only has two methods; psci and spin-table. Is this a problem? > Wouldn't it be better to help making U-Boot's PSCI stack as easy to use > as possible? I don't see technical reasons that adding PSCI support for > a board should be harder or more involved than adding spin-table support > - in the end you need to tell it about the SMP pen, maybe providing (or > faking?) reset and shutdown for 0.2 compliance. Right. My motivation is to bring up Linux quickly before ATF becomes ready. From your statement, I felt efforts for the ARMv8 PSCI implementation in U-Boot are underway. If so, I am definitely interested in it. -- Best Regards Masahiro Yamada _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
