linux-kernel - Re: Need suggestions for smp related properties in cpus.yaml to support smpboot for cortex-r52 based platform

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Mon, 15 May 2023 11:08:10 +0100
From:   Sudeep Holla <sudeep.holla@....com>
To:     Ayan Kumar Halder <ayankuma@....com>
Cc:     robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
        matthias.bgg@...il.com, angelogioacchino.delregno@...labora.com,
        geert+renesas@...der.be, magnus.damm@...il.com,
        konrad.dybcio@...aro.org, andersson@...nel.org,
        mazziesaccount@...il.com, conor.dooley@...rochip.com, j@...nau.net,
        mailingradian@...il.com, me@...ren.info, lpieralisi@...nel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org,
        linux-renesas-soc@...r.kernel.org, Julien Grall <julien@....org>,
        Stefano Stabellini <sstabellini@...nel.org>,
        Michal Orzel <michal.orzel@....com>,
        Sudeep Holla <sudeep.holla@....com>,
        Michal Simek <michal.simek@...inx.com>
Subject: Re: Need suggestions for smp related properties in cpus.yaml to
 support smpboot for cortex-r52 based platform

On Thu, May 11, 2023 at 10:35:37AM +0100, Ayan Kumar Halder wrote:
> Hi Device Tree engineers,
>
> Recently I have ported Xen on Cortex-R52 (AArch32-V8R processor) for our AMD
> platform.
>

I remember that there was some exploration on feasibility of using PSCI
here. What happened to that ? Any summary why that was dropped ?

> I was discussing with xen-devel community about how we can properly support
> smpboot when I was suggested that this might be the correct forum for
> discussion.
>
> Please refer
> https://lists.xenproject.org/archives/html/xen-devel/2023-05/msg00224.html
> and the follow-ups for context.
>
>
> The way smpboot works on our platform is as follows:-
>
> 1. core0 writes to register (say regA) the address of the secondary core
> initialization routine.
>
> 2. core0 writes to another register (say regB) the value "0x1" to put the
> secondary core in reset mode.
>
> 3. core0 writes to regB the value "0x0" to pull the secondary core out of
> reset mode.
>
> regA, regB will differ for core1, core2, core3 and so on.
>

Sounds OK but will you ever need to support power management on these cores ?
If so, just start with PSCI or provide reasons as why it doesn't fit well
before exploring and extending the existing spin table bindings.

>
> Currently, I am trying to bringup core1 only.
>
>
> I am thinking to use "enable-method=spin-table" in the cpu node for core1. 
> So that I can use "cpu-release-address" for regA.
>
> For regB, I am thinking of introducing a new property "amd-cpu-reset-addr"
> in the cpu node.
>
> Please let me know your thoughts on this approach. I am also open to any
> alternative suggestions.
>
>
> Also I see that in https://elixir.bootlin.com/linux/v6.4-rc1/source/Documentation/devicetree/bindings/arm/cpus.yaml#L87
> , "arm,cortex-r52" is missing.
>

Yes that should be fine IMO.

> Can I submit a patch (a one line change) to add this ?
>

Of course, it makes it easy to accept or reject rather than this question
hidden as part of other discussion.

--
Regards,
Sudeep