On Sat, Sep 12, 2020 at 2:25 AM Sean Anderson <[email protected]> wrote: > > On 9/11/20 10:43 AM, Bin Meng wrote: > > On Fri, Sep 11, 2020 at 6:20 PM Sean Anderson <[email protected]> wrote: > >> > >> On 9/11/20 3:29 AM, Bin Meng wrote: > >>> Hi Sean, > >>> > >>> On Sat, Sep 5, 2020 at 9:22 PM Sean Anderson <[email protected]> wrote: > >>>> > >>>> It is unsafe to enable OF_BOARD_FIXUP only based on OF_SEPARATE. > >>>> OF_SEPARATE may indicate that the user wishes U-Boot to use a different > >>>> device tree than one obtained via OF_PRIOR_STAGE. However, OF_SEPARATE > >>>> may > >>>> also indicate that the device tree which would be obtained via > >>>> OF_PRIOR_STAGE is invalid, nonexistant, or otherwise unusable. In this > >>> > >>> typo: nonexistent > >>> > >>>> latter case, enabling OF_BOARD_FIXUP will result in corruption of the > >>>> device tree. To remedy this, only enable OF_BOARD_FIXUP if U-Boot is > >>>> configured for S-Mode. > >>>> > >>>> Fixes: 1c17e55594a394ced7de88d91be294eaf8c564c1 > >>> > >>> nits: the format should be: commit_id ("description")> > >>>> Signed-off-by: Sean Anderson <[email protected]> > >>>> --- > >>>> > >>>> arch/riscv/Kconfig | 2 +- > >>>> 1 file changed, 1 insertion(+), 1 deletion(-) > >>>> > >>>> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig > >>>> index 009a545fcf..13fac51483 100644 > >>>> --- a/arch/riscv/Kconfig > >>>> +++ b/arch/riscv/Kconfig > >>>> @@ -288,6 +288,6 @@ config STACK_SIZE_SHIFT > >>>> default 14 > >>>> > >>>> config OF_BOARD_FIXUP > >>>> - default y if OF_SEPARATE > >>>> + default y if OF_SEPARATE && RISCV_SMODE > >>> > >>> Is that your board is running U-Boot M-mode with OF_SEPARATE that does > >>> not work? > >> > >> Yes, because the reason we use OF_SEPARATE is because no device tree is > >> passed to U-Boot. Trying to use the device tree passed to U-Boot even > > > > I don't get it. If no device tree is passed to U-Boot, why using > > OF_SEPARATE in the first place? > > Because it has to come from somewhere. Where else would U-Boot get the > device tree?
Sounds like there was some misunderstanding on "passed to U-Boot" .. But I got it now. > > >> though OF_SEPARATE is enabled results in garbage being written to the > > > > What garbage data is written? > > It might not be garbage written. I didn't document the exact failure > mode at the time I discovered this bug, so I went back to try and > reproduce it for a more thorough analysis. However, I was unable to > reproduce this bug, even on the branch where I originally triggered it. > I documented my reasoning behind this patch at [1]. In my testing, I > could only trigger a "periodic-32" bug. > > In any case, this behavior could still cause problems in the future. > From my testing, on the k210, a1 usually holds some address on the ROM's > stack. However, if it (for instance) instead held an address which So U-Boot on K210 boots with M-mode from the K210 ROM, and the ROM code does not hold DTB address in a1 before jumping to U-Boot, right? > raised a load access fault, or was misaligned, then booting would fail. > In the general case, I was very surpised that U-Boot was using the value > of a1 on entry even with OF_SEPARATE specified. I would expect it only > to use that value if configured with OF_PRIOR_STAGE. Because U-Boot S-mode needs to fix up the DT when OF_SEPERATE is used. > > --Sean > > [1] > https://patchwork.ozlabs.org/project/uboot/patch/[email protected]/#2520514 Regards, Bin
