Hi Troy Bin Meng <bmeng...@gmail.com> 於 2019年6月3日 週一 下午10:56寫道： > > Hi Troy, > > On Mon, Jun 3, 2019 at 10:53 PM Troy Benjegerdes > <troy.benjeger...@sifive.com> wrote: > > > > > > > > > On Jun 3, 2019, at 9:19 AM, Bin Meng <bmeng...@gmail.com> wrote: > > > > > > +Anup > > > > > > Hi Troy, > > > > > > On Mon, Jun 3, 2019 at 9:19 PM Troy Benjegerdes > > > <troy.benjeger...@sifive.com> wrote: > > >> > > >> > > >> > > >>> On Jun 2, 2019, at 9:22 PM, Rick Chen <rickche...@gmail.com> wrote: > > >>> > > >>> Hi Troy > > >>> > > >>>>> From: Troy Benjegerdes [mailto:troy.benjeger...@sifive.com] > > >>>>> Sent: Saturday, June 01, 2019 12:24 AM > > >>>>> To: Auer, Lukas > > >>>>> Cc: Rick Jian-Zhi Chen(陳建志); bmeng...@gmail.com; pal...@sifive.com > > >>>>> Subject: Re: Hart lottery and CONFIG_XIP > > >>>>> > > >>>>> > > >>>>> > > >>>>>> On May 31, 2019, at 9:13 AM, Auer, Lukas > > >>>>>> <lukas.a...@aisec.fraunhofer.de> > > >>>>> wrote: > > >>>>>> > > >>>>>> Hi Troy, > > >>>>>> > > >>>>>> On Fri, 2019-05-31 at 08:18 -0500, Troy Benjegerdes wrote: > > >>>>>>> Wouldn't the following line in head.S fail when running from flash > > >>>>>>> (although maybe not in a way that prevents booting) > > >>>>>>> > > >>>>>>> /* save the boot hart id to global_data */ > > >>>>>>> SREG tp, GD_BOOT_HART(gp) > > >>>>>>> > > >>>>>>> Shouldn’t this be protected by CONFIG_XIP? > > >>>>>> > > >>>>>> The boot hart ID is stored in global data, which is allocated from > > >>>>>> the > > >>>>>> stack (in board_init_f_alloc_reserve() ). It is therefore writable > > >>>>>> and > > >>>>>> won't cause any issues when running from flash. > > >>>>> > > >>>>> Sorry about the confusion, I was reading it wrong earlier. > > >>>>> > > >>>>> I’m hoping to have a couple of patches ready later today to change the > > >>>>> CONFIG_XIP patch to ‘CONFIG_HART_LOTTERY’ since it is also useful to > > >>>>> remove the potential indeterminism of which hart wins the lottery > > >>>>> when doing > > >>>>> board bringup and debugging. > > >>> > > >>> I am OK with that. > > >>> Actually my preliminary patch about > > >>> [PATCH 0/4] AE350 support SMP boot from flash > > >>> did as your wish. > > >>> > > >>> You can refer it : > > >>> [PATCH 1/4] riscv: hart_lottery and available harts feature can be > > >>> seletable > > >>> https://www.mail-archive.com/u-boot@lists.denx.de/msg323419.html > > >>> > > >>> Rick > > >> > > >> To follow up on > > >> https://www.mail-archive.com/u-boot@lists.denx.de/msg323526.html > > >> > > >> It is confusing and misleading to mix CONFIG_XIP and CONFIG_HART_LOTTERY. > > >> > > > > > > I am not sure what caused the confusion. CONFIG_XIP was added to > > > support U-Boot executing from ROM directly. > > > > > > > The confusion is use cases where you don’t necessarily need CONFIG_XIP, > > but you do want deterministic SMP booting, and the code is a lot more > > understandable > > with ‘#ifdef CONFIG_HART_LOTTERY’, and a Kconfig option and/or documentation > > warning that says CONFIG_HART_LOTTERY depends on !CONFIG_XIP > > > > OK, as I pointed out, the deterministic SMP booting was originally > posted, but later was changed to the lottery mechanism per Anup's > review comments. I am personally fine with both.
Yes. I am agree with that. But it shall also support booting form ROM and RAM as now. > > > >> From an system testing and validation point of view, I would find it > > >> much better > > >> (especially at very early boot stages, where U-boot might be the first > > >> non-ROM code > > >> running) to have a deterministic process to determine what core runs > > >> U-boot. This > > > > > > I remember when SMP patches were submitted by Lukas for the first time > > > it was deterministic using some macros like CONFIG_BOOT_HART, however > > > per Anup's request, the hart lottery feature, similar to what Linux > > > has, was added. > > > > I’d like to have CONFIG_BOOT_HART available as a config option as well, > > particularly > > for system validation testing. Also along those lines, if we are going to > > use a lottery > > to determine what CPU boots the system, how do we know afterwards which one > > it was? > > > > Yes, there is a way to know. Type 'dm tree' from U-Boot shell, then > look at which cpu node has a child node of "riscv_timer". Or you can check gd->arch.boot_hart by gdb (gdb) p/x gd->arch.boot_hart $3 = 0x0 B.R Rick > > Regards, > Bin _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de https://lists.denx.de/listinfo/u-boot
