On 03/03/2025 23:21, Ricardo Neri wrote: > On Fri, Sep 20, 2024 at 01:15:41PM +0200, Krzysztof Kozlowski wrote: > > [...] > >> enable-method is part of CPUs, so you probably should match the CPUs... >> I am not sure, I don't have the big picture here. >> >> Maybe if companies want to push more of bindings for purely virtual >> systems, then they should first get involved more, instead of relying on >> us. Provide reviews for your virtual stuff, provide guidance. There is >> resistance in accepting bindings for such cases for a reason - I don't >> even know what exactly is this and judging/reviewing based on my >> practices will no be accurate. > > Hi Krzysztof, > > I am taking over this work from Yunhong. > > First of all, I apologize for the late reply. I will make sure > communications are timely in the future. > > Our goal is to describe in the device tree a mechanism or artifact to boot > secondary CPUs. > > In our setup, the firmware puts secondary CPUs to monitor a memory location > (i.e., the wakeup mailbox) while spinning. From the boot CPU, the OS writes > in the mailbox the wakeup vector and the ID of the secondary CPU it wants > to boot. When a secondary CPU sees its own ID it will jump to the wakeup > vector. > > This is similar to the spin-table described in the Device Tree > specification. The key difference is that with the spin-table CPUs spin > until a non-zero value is written in `cpu-release-addr`. The wakeup mailbox > uses CPU IDs. > > You raised the issue of the lack of a `compatible` property, and the fact > that we are not describing an actual device. > > I took your suggestion of matching by node and I came up with the binding > below. I see these advantages in this approach: > > * I define a new node with a `compatible` property. > * There is precedent: the psci node. In the `cpus` node, each cpu@n has psci is a standard. If you are documenting here a standard, clearly express it and provide reference to the specification. > an `enable-method` property that specify `psci`. > * The mailbox is a device as it is located in a reserved memory region. > This true regardless of the device tree describing bare-metal or > virtualized machines. > > Thanks in advance for your feedback! > > Best, > Ricardo > > (only the relevant sections of the binding are shown for brevity) > > properties: > $nodename: > const: wakeup-mailbox > > compatible: > const: x86,wakeup-mailbox You need vendor prefix for this particular device. If I pointed out lack of device and specific compatible, then adding random compatible does not solve it. I understand it solves for you, but not from the bindings point of view. > > mailbox-addr: > $ref: /schemas/types.yaml#/definitions/uint64 So is this some sort of reserved memory? Mailbox needs mbox-cells, so maybe that's not mailbox. Best regards, Krzysztof
