cpu specific kernel call

[Michael Grunditz]

You can't run riscos on a m4, I am running on a53 core1. I will reply
better later today.

Den fre 5 mars 2021 12:08Stefan Kalkowski <stefan.kalkowski at genode-labs.com>
skrev:

> Hello Michael,
>
> On Wed, Mar 03, 2021 at 11:22:33PM +0100, Michael Grunditz wrote:
> > Hi,
> >
> > I have a kernel call that starts RISC OS, and uses psci. I wonder ,
> where
> > should I put that very aarch64 dependent code. I somehow need to be able
> > to call it from userspace.
> >
> > Regarding kernel calls in general , what is the best way of calling
> them?
> > Right now I do "MOV x0,#number ; SVC" , probably not very Genode style!
> :)
>
> Actually, there is already support for what you are looking for, I
> think. As far as I understood it correctly, you want to wake up the
> Cortex-M4 (side-) processor, after you've prepared RiscOS to run on top of
> it?
>
> Of course, you should not just add a system call that can be executed
> by every component to do something like this ;-). But we already had
> similar needs, when doing power control inside of the platform driver
> for i.MX 8M. There are some GPC controls that are done by the ARM
> Trusted firmware. Therefore we extended a previously existent
> privilege to the so called "managing_system" privilege that can be
> given when creating a new PD resp. component. This privilege is
> typically given only to the platform driver. With it a component can
> do a "managing_system(State&)" call on its PD session. This call transfers
> registers (State == Cpu_state) to core, which on will do a "secure
> monitor call" with the given registers (at least on ARMv8).
> For further understanding, please grep for "managing_system" inside
> base and base-hw.
>
> To sum it up, you could define a specific "Power_domain" for the M4 in
> the platform driver of your board, and then do the corresponding SMC
> call therein using the managing_system call. Your application doing
> the RiscOS loading just needs to acquire the device with the M4
> Power_domain from the platform driver at the point where you want to
> power it, and release it again when you want to power it off.
>
> This way, you will have a secure and sane integration of the M4
> handling.
>
> I hope I could somehow express myself comprehensivly.
>
> Best regards
> Stefan
>
> >
> >
> >
> >
> > --
> >        Michael Grunditz
> > Sent from my RISC OS workstation..
> >
> > _______________________________________________
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> > users at lists.genode.org
> > https://lists.genode.org/listinfo/users
>
> --
> Stefan Kalkowski
> Genode labs
>
> https://github.com/skalk | https://genode.org
>
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