在 2022-07-13星期三的 15:09 +0000，Conor.Dooley@xxxxxxxxxxxxx写道：
>
>
> On 13/07/2022 16:02, Icenowy Zheng wrote:
> > 在 2022-07-13星期三的 14:55 +0000，Conor.Dooley@xxxxxxxxxxxxx写道：
> > > On 13/07/2022 15:26, Icenowy Zheng wrote:
> > > >
> > > > 在 2022-07-11星期一的 19:43 +0100，Conor Dooley写道：
> > > > > From: Conor Dooley <conor.dooley@xxxxxxxxxxxxx>
> > > > >
> > > > > The JH7100 has a 32 bit monitor core that is missing from the
> > > > > device
> > > > > tree. Add it (and its cpu-map entry) to more accurately
> > > > > reflect
> > > > > the
> > > > > actual topology of the SoC.
> > > > >
> > > > > Signed-off-by: Conor Dooley <conor.dooley@xxxxxxxxxxxxx>
> > > > > ---
> > > > > arch/riscv/boot/dts/starfive/jh7100.dtsi | 21
> > > > > +++++++++++++++++++++
> > > > > 1 file changed, 21 insertions(+)
> > > > >
> > > > > diff --git a/arch/riscv/boot/dts/starfive/jh7100.dtsi
> > > > > b/arch/riscv/boot/dts/starfive/jh7100.dtsi
> > > > > index c617a61e26e2..92fce5b66d3d 100644
> > > > > --- a/arch/riscv/boot/dts/starfive/jh7100.dtsi
> > > > > +++ b/arch/riscv/boot/dts/starfive/jh7100.dtsi
> > > > > @@ -67,6 +67,23 @@ cpu1_intc: interrupt-controller {
> > > > > };
> > > > > };
> > > > >
> > > > > + E24: cpu@2 {
> > > > > + compatible = "sifive,e24", "riscv";
> > > > > + reg = <2>;
> > > > > + device_type = "cpu";
> > > > > + i-cache-block-size = <32>;
> > > > > + i-cache-sets = <256>;
> > > > > + i-cache-size = <16384>;
> > > > > + riscv,isa = "rv32imafc";
> > > > > + status = "disabled";
> > > > > +
> > > > > + cpu2_intc: interrupt-controller {
> > > > > + compatible = "riscv,cpu-
> > > > > intc";
> > > > > + interrupt-controller;
> > > > > + #interrupt-cells = <1>;
> > > > > + };
> > > > > + };
> > > > > +
> > > > > cpu-map {
> > > > > cluster0 {
> > > > > core0 {
> > > > > @@ -76,6 +93,10 @@ core0 {
> > > > > core1 {
> > > > > cpu = <&U74_1>;
> > > > > };
> > > > > +
> > > > > + core2 {
> > > > > + cpu = <&E24>;
> > > > > + };
> > > >
> > > > Sorry but I think this change makes the topology more
> > > > inaccurate.
> > > >
> > > > The E24 core is very independent, just another CPU core
> > > > connected
> > > > the
> > > > same bus -- even no coherency (E24 takes AHB, which is not
> > > > coherency-
> > > > sensible). Even the TAP of it is independent with the U74 TAP.
> > > >
> > > > And by default it does not boot any proper code (if a debugger
> > > > is
> > > > attached, it will discover that the E24 is in consistently
> > > > fault at
> > > > 0x0
> > > > (mtvec is 0x0 and when fault it jumps to 0x0 and fault again),
> > > > until
> > > > its clock is just shutdown by Linux cleaning up unused clocks.)
> > > >
> > > > Personally I think it should be implemented as a remoteproc
> > > > instead.
> > >
> > > Maybe I am missing something, but I don't quite get what the
> > > detail
> > > of how we access this in code has to do with the devicetree?
> > > It is added here in a disabled state, and will not be used by
> > > Linux.
> > > The various SiFive SoCs & SiFive corecomplex users that have a
> > > hart
> > > not capable of running Linux also have that hart documented in
> > > the
> > > devicetree.
> > > To me, what we are choosing to do with this hart does not really
> > > matter very much, since this is a description of what the
> > > hardware
> > > actually looks like.
> >
> > The E24 is not in the core complex at all. It's just a dedicate CPU
> > connected to another bus (well as I saw the document says the E24
> > bus
> > is maximum 2G, I doubt whether it's the same bus with the U74 one).
> >
> > The U74 MC only allows S5 management cores to be part of it, not
> > E24.
>
> So is the correct topology more like:
> cpu-map {
> cluster0 {
> core0 {
> cpu = <&U74_0>;
> };
> core1 {
> cpu = <&U74_1>;
> };
> };
> cluster1 {
> core0 {
> cpu = <&E24>;
> };
> };
> };
Considering E24 seems to see a total different bus connected to it, I
don't think it even proper to add it to cpus node.
And I don't think it has a hart id of 2, as your node describes.
>
