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. Rick > > Where SPL loads SBI and U-Boot and tells SBI "please run U-Boot after you are > done booting". But the idea here is to load Linux instead of U-Boot. I think > this is pretty similar to Falcon mode. Actually, when CONFIG_SPL_OPENSBI is > enabled, I think it's reasonable for falcon mode to do exactly that. People > who want the SPL -> Linux path can disable SPL_OPENSBI. > > --Sean
