[U-Boot] [PATCH 12/12] riscv: Add QEMU virt board support

[Rick Chen]

Bin Meng <bmeng.cn at gmail.com> 於 2018年9月5日 週三 上午10:34寫道：
>
> Hi Rick,
>
> On Wed, Sep 5, 2018 at 9:27 AM Rick Chen <rickchen36 at gmail.com> wrote:
> >
> >  > > From: Auer, Lukas [mailto:lukas.auer at aisec.fraunhofer.de]
> >  > > Sent: Wednesday, September 05, 2018 5:53 AM
> >  > > To: bmeng.cn at gmail.com
> >  > > Cc: Rick Jian-Zhi Chen(陳建志); u-boot at lists.denx.de
> >  > > Subject: Re: [U-Boot] [PATCH 12/12] riscv: Add QEMU virt board support
> >  > >
> >  > > On Tue, 2018-09-04 at 17:31 +0800, Bin Meng wrote:
> >  > > > Hi Lukas,
> >  > > >
> >  > > > On Tue, Sep 4, 2018 at 5:39 AM Auer, Lukas
> >  > > > <lukas.auer at aisec.fraunhofer.de> wrote:
> >  > > > >
> >  > > > > On Thu, 2018-08-30 at 00:54 -0700, Bin Meng wrote:
> >  > > > > > This adds QEMU RISC-V 'virt' board target support, with the hope
> >  > > > > > of helping people easily test U-Boot on RISC-V.
> >  > > > > >
> >  > > > > > The QEMU virt machine models a generic RISC-V virtual machine
> >  > > > > > with support for the VirtIO standard networking and block
> >  > > > > > storage devices.
> >  > > > > > It has CLINT, PLIC, 16550A UART devices in addition to VirtIO
> >  > > > > > and it also uses device-tree to pass configuration information
> >  > > > > > to guest software. It implements RISC-V privileged architecture
> >  > > > > > spec v1.10.
> >  > > > > >
> >  > > > > > Both 32-bit and 64-bit builds are supported. Support is pretty
> >  > > > > > much preliminary, only booting to U-Boot shell with the UART
> >  > > > > > driver on a single core. Booting Linux is not supported yet.
> >  > > > > >
> >  > > > >
> >  > > > > For your information and to avoid duplicate work, I am working on
> >  > > > > a patch set that improves RISC-V support in u-boot. I am currently
> >  > > > > able to boot Linux on a multi-core setup in QEMU, but they are not
> >  > > > > quite ready to submit yet.
> >  > > > >
> >  > > >
> >  > > > This is great! My next step is to work on virtio driver support in
> >  > > > U-Boot as qemu-riscv virt machine has these devices but we don't
> >  > > > have corresponding drivers in U-Boot. Then I will try to boot Linux
> >  > > > after that. Good to hear you already boot Linux with qemu-riscv!
> >  > > > Have you already supported virtio drivers in your port? If yes, I
> >  > > > will just hold on and wait for your patch series :-)
> >  > > >
> >  > >
> >  > > Hi Bin,
> >  > >
> >  > > Support for the virtio devices would be great! I don't support them in
> >  > > my port, I can only boot a kernel image from RAM.
> >  > > I only have a driver for the clint0 (core local interrupt controller),
> >  > > which I need for software interrupts to other cores and as a timer.
> >  > > Software interrupts also work over the supervisor binary interface
> >  > > (SBI), which allows u-boot to run in supervisor mode with bbl running
> >  > > in machine mode to handle the SBI calls.
> >  > >
> >
> > Hi Bin and Auer
> >
> > I have already boot bbl run in S-mode and riscv-linux in M-mode via
> > u-boot from SD card or FLASH.
> > It mean after booting riscv-linux, u-boot will be dead. And no matter
> > about kernel.
> > Please refer to doc/README.ae350
> >
>
> Thanks for pointing out the doc for ae350. I just read it, and have
> one question. There is a chapter in that doc "Boot bbl and riscv-linux
> via U-Boot on QEMU", yet I don't see what QEMU command is invoked. Can
> you please clarify? AFAIK mainline QEMU does not have support to ae350
> board. Also there is no instructions on how bbl was built. Is that the
> mainline bbl that can work on every riscv board? I doubt that.
>

There are some teammates who are responsible for bbl, riscv-linux,
u-boot, qemu individually.
As I know they just pull source from mainline and have relative hooks
for ax25-ae350.
I am in charge of booting kernel via u-boot.
And drivers (timer, serial, spi flash, smc flash, sd, mac, rtc,
wdt,i2c, sound, lcd) verification on u-boot and kernel.
That is why I am pending u-boot for a while.

When I finish booting riscv-linux via u-boot function. Then I have
pushed them to u-boot upstream.
And describe simply the build and run flow in doc/README.ae350.
As I know, the implementations about bbl and qemu still not been
pushed to upstream yet.
Maybe I can ask them how about the upstream schedule !

Hope this can answer your question !

> > May I figure out more clearly what are you going to do ?
> > What are you going to do is let u-boot run in S-mode and boot bbl and
> > riscv-linux in M-mode, right ?
>
> I want to use U-Boot to directly boot Linux, but seems Lukas is using
> bbl for SBI implementation.
>
> > It mean after booting bbl and riscv-linux, u-boot will still alive and
> > handle SBI calls and somethings in S-mode.
> >
> > Or u-boot is going to replace the role of bbl ?
> >
>
> That's my plan. I don't see a need to use bbl which is quite feature limited.
>

Sounds great !
Very looking forward to this achievement !

Rick

> Regards,
> Bin