On Tue, Dec 13, 2022 at 08:42:47AM +0800, Rick Chen wrote: > Hi Sean, > > > On 12/12/22 10:03, Tom Rini wrote: > > > On Mon, Dec 12, 2022 at 02:45:10PM +0800, Rick Chen wrote: > > >> Hi Tom > > >> > > >>> On Fri, Dec 09, 2022 at 08:48:37AM -0500, Sean Anderson wrote: > > >>>> On 12/7/22 01:23, Rick Chen wrote: > > >>>>> In RISC-V, it only provide normal mode booting currently. > > >>>>> To speed up the booting process, here provide SPL_OPENSBI_OS_BOOT > > >>>>> to achieve this feature which will be call Fast-Boot mode. By > > >>>> > > >>>> Can you name this something different. We already have something called > > >>>> fastboot in-tree (the Android-derived protocol) and there's a Microsoft > > >>>> technology called fastboot (some kind of hibernation). "OS Boot" isn't > > >>>> very specific either, since we (almost always) boot an OS. Maybe "Eagle > > >>>> mode" by analogy to Falcon mode, which lets SPL directly boot an OS. > > >>>> > > >>>> (Is this substantially different from falcon mode anyway?) > > >>> > > >>> I was kind of wondering if this is different, really, from Falcon Mode. > > >>> Falcon Mode didn't initially have to factor in other-firmware as that's > > >>> not a hard requirement on arm32 like it is on arm64 or risc-v. But my > > >>> first read of this was that it seems like the RISC-V specific side of > > >>> doing Falcon Mode and dealing with the prior stage needs correctly. > > >>> > > >> > > >> Yes. It is a little bit different from the Falcon mode (SPL_OS_BOOT=y). > > >> When I try to enable SPL_OS_BOOT, it will encounter that > > >> SYS_SPL_ARGS_ADDR and > > >> jump_to_image_linux() shall be defined but they are un-necessary for > > >> RISC-V. > > >> Because the flow of OpenSBI and SPL_OS_BOOT are totally different code > > >> flow in board_init_r() of common/spl/spl.c. > > >> That is why I added a new symbol called SPL_OPENSBI_OS_BOOT for this > > >> RISC-V fast boot implementation. > > > > > > Those sound like fairly minor challenges for the same fundamental > > > concept. We have SYS_SPL_ARGS_ADDR for "where is the device tree to > > > pass along". We might need to do a little code re-factoring here. But > > > maybe also a little bit of explaining why we wouldn't be booting to the > > > OS directly but instead passing back to openSBI to do this? That's not > > > normally how RISC-V boots the OS, right? Or am I miss-understanding > > > something here? > > > > > > > The usual process is > > > > ROM -> SPL -> SBI -> U-Boot -> Linux > > In RISC-V, Linux runs in S-mode, it needs the OpenSBI which plays as > M-mode to deal with SBI calls at run-time. > So the fast boot idea, I just want to bypass U-Boot and jump to Linux > directly and Linux still needs OpenSBI. > Hence SPL_OPENSBI can't be disabled here.
So is the flow here: a) ROM -> SPL -> SBI -> SPL -> Linux or b) ROM -> SPL -> SBI -> Linux It's not clear to me, and I think that'll help figure out what's best here. Since I kinda think we're looking at a more generic issue that we see with newer architectures and maybe we already had to solve this (but didn't name things well enough) for aarch64. -- Tom
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