Thanks Nathan! I'm still getting used to NuttX Kernel Mode and RISC-V Machine / Supervisor Modes, so I thought I might stick with QEMU Kernel Mode and make it work on Star64.
But you're right, when I'm more familiar with Star64, I ought to explore more of CONFIG_ARCH_USE_S_MODE and RISC-V Machine Mode :-) Lup On Wed, Jul 19, 2023 at 10:25 AM Nathan Hartman <hartman.nat...@gmail.com> wrote: > On Tue, Jul 18, 2023 at 7:33 PM Lee, Lup Yuen <lu...@appkaki.com> wrote: > > > We’re in the super-early stage of porting NuttX to the Pine64 Star64 > 64-bit > > RISC-V SBC. (Based on StarFive JH7110 SoC) > > > > In this article we’ll talk about the interesting things that we learnt > > about RISC-V and Star64 JH7110… > > > > (1) What are RISC-V Privilege Levels > > (And why they make NuttX a little more complicated) > > > > (2) What is NuttX Kernel Mode > > (And how it differs from Flat Mode) > > > > (3) All about JH7110’s UART Registers > > (And how they are different from other 16550 UARTs) > > > > (4) Why (naively) porting NuttX from QEMU to Star64 might become really > > challenging! > > (Thankfully we have the LiteX Arty-A7 and PolarFire Icicle ports) > > > > https://lupyuen.codeberg.page/articles/privilege.html > > > > Lup > > > > Beautiful article! > > Question: In section 6, "NuttX flat mode becomes kernel mode," isn't it > possible to set CONFIG_ARCH_USE_S_MODE for the FLAT build as well? Since > the board's built-in firmware switches from Machine Mode to Supervisor Mode > before calling U-Boot -> NuttX, I think that all configurations running on > this board should select CONFIG_ARCH_USE_S_MODE by default. This can be set > in Kconfig by default whenever this board is selected, so there is no need > to remember and add it in multiple places/configs; however if someone > figures out an alternative firmware that lets us boot NuttX on this board > in Machine Mode, it will be easy to override. Just a thought... > > Thanks for a great article as always! > > Cheers, > Nathan >
