Re: [Qemu-devel] [PATCH v1 1/4] hw/riscv/sifive_u: Create a U54 SoC object

[Alistair Francis <alistair23@gmail.com>]

On Fri, May 4, 2018 at 3:55 PM, Michael Clark <mjc@sifive.com> wrote:
>
>
> On Sat, May 5, 2018 at 8:12 AM, Alistair Francis <alistair.francis@wdc.com>
> wrote:
>>
>> Create a SiFive Unleashed U54 SoC and use that in the sifive_u machine.
>>
>> We leave the SoC, RAM, device tree and reset/fdt loading as part of the
>> machine. All the other device creation has been moved to the SoC.
>
>
> There is a tiny problem that we will have to resolve with renaming,
> otherwise we will end up with lots of SOCs that are the essentially same
> with a different CPU.
>
> There is an intention to add a HiFive1 and HiFiveU board in the future
> however we were very explicit in renaming sifive_e300 and sifive_u500 to
> sifive_e and sifive_u.
>
> If you read the code more closely you'll notice that we instantiate the
> sifive_u board with a U34 if 32-bit and a U54 if 64-bit.
>
> #if defined(TARGET_RISCV32)
> #define SIFIVE_U_CPU TYPE_RISCV_CPU_SIFIVE_U34
> #elif defined(TARGET_RISCV64)
> #define SIFIVE_U_CPU TYPE_RISCV_CPU_SIFIVE_U54
> #endif
>
> The rationale is that sifive_e and sifive_u can eventually be customized to
> represent different configurations of SiFive Core IP. We won't want to end
> up hardcoding specific models in sifive_e or sifive_u
>
> SiFive have been talking internally about having sifive_e and sifive_u
> reconfigurable, possibly even to the extend where we can configure with a
> memory map. This is somewhat consistent with what SiFive do internally as
> the FE310 and FU540 are configurations generated by a core generator.
>
> Now comes the question of whether its the right time to add a 'hifive1' or
> 'hifiveu' machine. I don't think it is immediately necessary. The thought
> being that we would be able to give a configuration string of file to
> sifive_u e.g. "e51,u54,u54,u54". There is a different between the U54 and
> the U54-MC which has an E51 core for management tasks. The PLIC has already
> been written with this in mind, and is re-configurable to support the U54-MC
> memory layout.

Aren't the E51, U54, U54-MC, etc. all different SoCs? So doesn't it
make sense to break out the SoCs and then in future the user can
specify the SoC for the machine/board when they start QEMU?

Alistair

>
> In anycase. The change is simply to use sifive_u_soc or sifive_u without the
> 54 (given it configures with a U34 in 32-bit like the sifive_e configures
> with an E51 in 64-bit mode, both valid configurations)
>