Hi Tom > 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?
Because RISC-V Linux runs in S-Mode, it needs OpenSBI which runs in M-mode to handle SBI calls. So it can not boot Linux (OS) directly from U-Boot SPL but passing back to openSBI to do this. Rick > > -- > Tom