Hi Sudeep,
On 15/05/2023 11:08, Sudeep Holla wrote:
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 ?
We are discussing internally with other Xilinx/AMD engineers about this.
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.
Power management is not in scope.
About PSCI, we are discussing internally.
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.
I have submitted a patch for this.
https://archive.armlinux.org.uk/lurker/message/20230518.152730.c91cc994.en.html
- Ayan
--
Regards,
Sudeep
