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Re: [PATCH v2 9/9] hw/riscv: virt: Set the clock-frequency


From: Alistair Francis
Subject: Re: [PATCH v2 9/9] hw/riscv: virt: Set the clock-frequency
Date: Tue, 21 Dec 2021 16:32:23 +1000

On Mon, Dec 20, 2021 at 5:52 PM Bin Meng <bmeng.cn@gmail.com> wrote:
>
> On Thu, Dec 16, 2021 at 12:55 PM Alistair Francis
> <alistair.francis@opensource.wdc.com> wrote:
> >
> > From: Alistair Francis <alistair.francis@wdc.com>
> >
> > As per the device tree specification let's set the clock-frequency for
> > the virt CPUs.
> >
> > QEMU doesn't really have an exact clock, so let's just 1000000 as it's a
> > nice round number and matches the sifive_u CLINT_TIMEBASE_FREQ.
> >
> > Resolves: https://gitlab.com/qemu-project/qemu/-/issues/472 (RISC-V virt)
>
> I tend to think this issue is not valid, as the comment in the issue
> says the value should reflect the running frequency.
>
> Note the "clock-frequency" was once in the codes but was intentionally
> removed before because it is not needed:
>
> See commit 7ae05377b85f (" riscv: hw: Drop "clock-frequency" property
> of cpu nodes")

Hmmm... Good point.

But if the device tree spec says it's required then I think we should
include it. Even if it isn't super relevant for us

Alistair

>
> > Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
> > ---
> >  hw/riscv/virt.c | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > diff --git a/hw/riscv/virt.c b/hw/riscv/virt.c
> > index 3af074148e..41a85cfc60 100644
> > --- a/hw/riscv/virt.c
> > +++ b/hw/riscv/virt.c
> > @@ -202,6 +202,7 @@ static void create_fdt_socket_cpus(RISCVVirtState *s, 
> > int socket,
> >          qemu_fdt_setprop_cell(mc->fdt, cpu_name, "reg",
> >              s->soc[socket].hartid_base + cpu);
> >          qemu_fdt_setprop_string(mc->fdt, cpu_name, "device_type", "cpu");
> > +        qemu_fdt_setprop_cell(mc->fdt, cpu_name, "clock-frequency", 
> > 1000000);
> >          riscv_socket_fdt_write_id(mc, mc->fdt, cpu_name, socket);
> >          qemu_fdt_setprop_cell(mc->fdt, cpu_name, "phandle", cpu_phandle);
>
> Regards,
> Bin



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