[U-Boot] [PATCH 4/8] riscv: andes_plic: Fix some wrong configurations

Thu Nov 7 05:15:45 UTC 2019

On Thu, Nov 7, 2019 at 7:04 AM Rick Chen <rickchen36 at gmail.com> wrote:
>
> Hi Anup
>
> > On Wed, Nov 6, 2019 at 2:51 PM Rick Chen <rickchen36 at gmail.com> wrote:
> > >
> > > Hi Anup
> > >
> > > >
> > > > On Wed, Nov 6, 2019 at 2:18 PM Anup Patel <anup at brainfault.org> wrote:
> > > > >
> > > > > On Wed, Nov 6, 2019 at 12:14 PM Rick Chen <rickchen36 at gmail.com> wrote:
> > > > > >
> > > > > > Hi Anup
> > > > > >
> > > > > > >
> > > > > > > On Tue, Nov 5, 2019 at 7:19 AM Rick Chen <rickchen36 at gmail.com> wrote:
> > > > > > > >
> > > > > > > > Hi Anup
> > > > > > > >
> > > > > > > > > > On Thu, Oct 31, 2019 at 1:42 PM Anup Patel <anup at brainfault.org> wrote:
> > > > > > > > > > >
> > > > > > > > > > > On Thu, Oct 31, 2019 at 6:30 AM Alan Kao <alankao at andestech.com> wrote:
> > > > > > > > > > > >
> > > > > > > > > > > > Hi Bin,
> > > > > > > > > > > >
> > > > > > > > > > > > Thanks for the critics.  Comments below.
> > > > > > > > > > > > On Wed, Oct 30, 2019 at 06:38:00PM +0800, Bin Meng wrote:
> > > > > > > > > > > > > Hi Rick,
> > > > > > > > > > > > >
> > > > > > > > > > > > > On Wed, Oct 30, 2019 at 10:50 AM Rick Chen <rickchen36 at gmail.com> wrote:
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > Hi Bin
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > Hi Rick,
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > On Fri, Oct 25, 2019 at 2:18 PM Andes <uboot at andestech.com> wrote:
> > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > From: Rick Chen <rick at andestech.com>
> > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > It will work fine due to hart 0 always will be main
> > > > > > > > > > > > > > > > hart coincidentally. When develop SPL flow, I try to
> > > > > > > > > > > > > > > > force other harts to be main hart. And it will go
> > > > > > > > > > > > > > > > wrong in sending IPI flow. So fix it.
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > Fix what? Does this commit contain 2 fixes, or just 1 fix?
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > Yes, it include two fixs. But they will cause one negative result
> > > > > > > > > > > > > > that only hart 0 can send ipi to other harts.
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > Having this fix, any hart can be main hart in U-Boot SPL
> > > > > > > > > > > > > > > > theoretically, but it still fail somewhere. After dig in
> > > > > > > > > > > > > > > > and found there is an assumption that hart 0 shall be
> > > > > > > > > > > > > > > > main hart in OpenSbi.
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > So does this mean there is a bug in OpenSBI too?
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > I am not sure if it is a bug. Maybe it is a compatible issue.
> > > > > > > > > > > > > > There is a limitation that only hart 0 can be main hart in OpenSBI.
> > > > > > > > > > > > >
> > > > > > > > > > > > > I don't think OpenSBI has such limitation.
> > > > > > > > > > > > >
> > > > > > > > > > > >
> > > > > > > > > > > > Please check the source.
> > > > > > > > > > > > https://github.com/riscv/opensbi/blob/master/firmware/fw_base.S#L54
> > > > > > > > > > > >
> > > > > > > > > > > > Apparently, the FIRST TWO LINEs of the initialization are the
> > > > > > > > > > > > 1. get hart ID.
> > > > > > > > > > > > 2. determine which route to take based on their ID respectively.
> > > > > > > > > > > >
> > > > > > > > > > > > So, I do think OpenSBI has this signature, if you are not willing to call it
> > > > > > > > > > > > a limitation.
> > > > > > > > > > >
> > > > > > > > > > > This dependency on hart id #0 was not there until we added self-relocation
> > > > > > > > > > > in OpenSBI for FW_DYNAMIC.
> > > > > > > > > > >
> > > > > > > > > > > I will try to fix this in OpenSBI but we might end-up having boot_lottery.
> > > > > > > > > >
> > > > > > > > > > I have send a patch to fix this OpenSBI:
> > > > > > > > > > "[PATCH] firmware: Introduce relocation lottery"
> > > > > > > > > >
> > > > > > > > > > Can you try above patch and see if that helps ?
> > > > > > > > > >
> > > > > > > > > > It will be great if you can provide Tested-by to my patch as well.
> > > > > > > > > >
> > > > > > > > >
> > > > > > > >
> > > > > > > > I can not find this patch in mailing list.
> > > > > > > > Can you provide a hyperlink ?
> > > > > > >
> > > > > > > You can try latest riscv/opensbi master.
> > > > > > >
> > > > > > > I have tested the patch on SiFive Unleashed multiple times.
> > > > > >
> > > > > > I have tried this patch, but it fail
> > > > > > firmware: Introduce relocation lottery(
> > > > > > 98f4a208995b027662a7b04a25e4fa5df5f3eefe)
> > > > > >
> > > > > > The scenario was as below:
> > > > > > There are 4 harts run in U-Boot SPL, hart 0 play as main hart.
> > > > > > The hart 1 will receive ipi and come into OpenSBI(0x1000000) from
> > > > > > U-Boot SPL(0x0), meanwhile hart 0,2,3 still run in U-Boot SPL.
> > > > > > Then hart 1 will do _relocate_copy_to_lower which will copy data from
> > > > > > 0x1000000 to 0x0.
> > > > > > And it will corrupt U-Boot SPL.
> > > > >
> > > > > The self-relocation in OpenSBI firmwares ensures that OpenSBI firmware
> > > > > are moved to the FW_TEXT_START before entering C code. This helps
> > > > > us load OpenSBI firmwares anywhere in RAM.
> > > > >
> > > > > However, OpenSBI firmwares don't know where the U-Boot SPL is running.
> > > > >
> > > > > In your case, both OpenSBI FW_DYNAMIC and U-Boot SPL are linked to
> > > > > address same address 0x0. This means secondary HARTs cannot safely
> > > > > wait while primary HART enters OpenSBI. You should hold secondary HARTs
> > > > > in U-Boot SPL only till OpenSBI FW_DYNAMIC and U-Boot proper are
> > > > > loaded in RAM by primary HART. All your HARTs should jump to OpenSBI
> > > > > at the same time after everything is loaded in RAM.
> > > >
> > > > I see the issue now.
> > > >
> > > > The U-Boot SPL is first letting secondary HART jump to OpenSBI and primary
> > > > HART jumps to OpenSBI at the end.
> > > > (Refer, jump_to_image_no_args() in arch/riscv/lib/spl.c)
> > > >
> > > > The real issue is FW_TEXT_START being same as U-Boot SPL TEXT_START.
> > > >
> > > > If possible please change TEXT base for U-Boot SPL or OpenSBI. I think
> > > > changing U-Boot SPL TEXT_START would be convenient since this series
> > > > is under review. Thoughts ?
> > >
> > > Yes.
> > > I know it can avoid corrupting issue with changing  U-Boot SPL
> > > TEXT_START not equal to OpenSBI TEXT base.
> >
> > I think this issue will be seen on U-Boot SPL running on QEMU as well.
> >
> > >
> > > With the following changes, U-Boot SPL text base can equal to OpenSBI text base
> > > 1 U-Boot pass main hart information (a2) when jumping to OpenSBI
> > > 2 OpenSBI pick up $a2 to keep playing as main hart, other harts go to
> > > _wait_relocate_copy_done
> >
> > Overall it's a good suggestion but we cannot use a2 register because this
> > will break FW_JUMP and FW_PAYLOAD. Instead, we should pass preferred
> > boot HART id in struct fw_dynamic_info.
>
> Sorry, what I want to say shall be a3.
>
> >
> > I have a patch for this in preferred_boot_hart_v1 branch of
> > https://github.com/avpatel/opensbi.git
> >
> > Can you try OpenSBI from above branch ?
> >
> > You will have to update the "struct fw_dynamic_info" passed to
> > OpenSBI by U-Boot SPL.
>
> Main hart will pass struct "fw_dynamic_info" to OpenSBI by U-Boot SPL.
> But other harts will NOT pass struct "fw_dynamic_info" to OpenSBI by U-Boot SPL.

That's wrong in U-Boot SPL.

All HARTs have to follow FW_DYNAMIC protocol and pass
"struct fw_dynamic_info" pointer in 'a2' register.

>
> So if U-Boot SPL can pass main hart information via a3, OpenSBI just
> have the following change
> blt zero, a6, _wait_relocate_copy_done
> change to
> bne a3, a6, _wait_relocate_copy_done
> before this commit
> 98f4a208995b027662a7b04a25e4fa5df5f3eefe
> firmware: Introduce relocation lottery

What about FW_JUMP and FW_PAYLOAD? We have no way of passing
value in a3 for these firmwares because these are not booted by U-Boot
SPL.

Also, U-Boot-2019.10 already uses U-Boot SPL support which does not
pass anything in 'a3' register.

We should definitely use "struct fw_dynamic_info" for this so that we can
maintain backward compatibility as well.

Please make sure that U-Boot SPL passes "struct fw_dynamic_info"
pointer in 'a2' register for all HARTs.

>
> But after this commit 98f4a, main hart become chosen from lottery mechanism.
> Maybe I will prefer to change U-Boot SPL text base not overlap with
> OpenSBI text start. :)

Like I mentioned, we have this issue for U-Boot SPL on QEMU as well. It's
just that most of us did not notice it for U-Boot SPL on QEMU.

Let's fix this in the right way from start itself.

Regards,
Anup

>
> Thanks
> Rick
>
> >
> > Meanwhile, I will try above patch on QEMU and SiFive Unleashed.
> >
> > >
> > > It will be convenient to change U-Boot SPL text base currently.
> >
> > Let's fix this correctly now itself.
> >
> > Regards,
> > Anup