Hi Stefano, Oleksii,
Stefano Stabellini <sstabell...@kernel.org> writes: > On Wed, 22 Dec 2021, Oleksii Moisieiev wrote: >> On Tue, Dec 21, 2021 at 01:22:50PM -0800, Stefano Stabellini wrote: >> > On Tue, 21 Dec 2021, Oleksii Moisieiev wrote: >> > > Hi Stefano, >> > > >> > > On Mon, Dec 20, 2021 at 04:52:01PM -0800, Stefano Stabellini wrote: >> > > > On Mon, 20 Dec 2021, Oleksii Moisieiev wrote: >> > > > > Hi Stefano, >> > > > > >> > > > > On Fri, Dec 17, 2021 at 06:14:55PM -0800, Stefano Stabellini wrote: >> > > > > > On Tue, 14 Dec 2021, Oleksii Moisieiev wrote: [...] >> > > > In general we can't use properties that are not part of the device tree >> > > > spec, either >> > > > https://urldefense.com/v3/__https://www.devicetree.org/specifications/__;!!GF_29dbcQIUBPA!kNodtgmOQBc1iO76_6vTK-O1SoLxee_ChowYQiQYC595rMOsrnmof2zmk7BnhXCSnJPN$ >> > > > [devicetree[.]org] or >> > > > https://urldefense.com/v3/__https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/devicetree/bindings__;!!GF_29dbcQIUBPA!kNodtgmOQBc1iO76_6vTK-O1SoLxee_ChowYQiQYC595rMOsrnmof2zmk7BnhXloYUaj$ >> > > > [git[.]kernel[.]org] >> > > > >> > > > "linux,scmi_mem" is currently absent. Are you aware of any upstreaming >> > > > activities to get "linux,scmi_mem" upstream under >> > > > Documentation/devicetree/bindings in Linux? >> > > > >> > > > If "linux,scmi_mem" is going upstream in Linux, then we could use it. >> > > > Otherwise, first "linux,scmi_mem" needs to be added somewhere under >> > > > Documentation/devicetree/bindings (probably >> > > > Documentation/devicetree/bindings/firmware/arm,scmi.yaml), then we can >> > > > work on the Xen code that makes use of it. >> > > > >> > > > Does it make sense? >> > > > >> > > >> > > Yes I agree. I think linux,scmi_mem and scmi_devid should be upstreamed. >> > > I will add those properties to arm,scmi.yaml, mark them as related to >> > > XEN and send patch. >> > >> > I didn't realize that linux,scmi_mem and scmi_devid are supposed to be >> > Xen specific. In general, it would be best not to introduce Xen specific >> > properties into generic bindings. It is a problem both from a >> > specification perspective (because it has hard to handle Xen specific >> > cases in fully generic bindings, especially as those bindings are >> > maintained as part of the Linux kernel) and from a user perspective >> > (because now the user has to deal with a Xen-specific dtb, or has to >> > modify the host dtb to add Xen-specific information by hand.) >> > >> > >> > Let me start from scmi_devid. Why would scmi_devid be Xen-specific? It >> > looks like a generic property that should be needed for the Linux SCMI >> > driver too. Why the Linux driver doesn't need it? >> > >> >> scmi_devid used during domain build. It passed as input parameter for >> SCMI_BASE_SET_DEVICE_PERMISSIONS message. >> On non-virtualized systems - there is no need of this call, because OS >> is the only one entity, running on the system. > > OK. Even if it is only required for virtualized systems, I think that > scmi_devid is important enough that should be part of the upstream > binding. I think it is worth starting an email thread on the LKML with > Rob Herring and the SCMI maintainers to discuss the addition of > scmi_devid to the binding. Agree there. Also I want to point that there are other hypervisors, like KVM, which may benefit from this. Another approach is to name this node "xen,scmdi_devid", but I don't like it. >> I've chatted with Volodymyr_Babchuk and he gave a great idea to add a >> list of device_ids to dom.cfg, such as: >> sci_devs = [ 0, 1, 15, 35 ]; >> Well, yes. We discussed this possibility, but personally I stick to idea of re-using dt_dev, as we discussed in the different thread. >> Using this approach, we can remove scmi_devid from the device tree and >> just pass a list of scmi_devids to XEN using additional hypercall. >> We can probably make hypercall taking devid list as input parameter. >> This will take only 1 hypercall to setup sci permissions. > > But how would a user know which are the right SCMI IDs to add to the > sci_devs list? Would the user have to go and read the reference manual > of the platform to find the SCMI IDs and then write sci_devs by hand? > If that is the case, then I think that it would be better to add > scmi_devid to device tree. > Yes, ideally this needs to be done by BSP vendor in the device tree. -- Volodymyr Babchuk at EPAM
