On Thu 21 May 12:29 PDT 2020, Suman Anna wrote: > On 5/21/20 2:21 PM, Bjorn Andersson wrote: > > On Thu 21 May 12:06 PDT 2020, Suman Anna wrote: > > > > > Hi Bjorn, > > > > > > On 5/21/20 12:54 PM, Bjorn Andersson wrote: > > > > On Wed 25 Mar 13:46 PDT 2020, Suman Anna wrote: > > > > > > > > > The current remoteproc core has supported only 32-bit remote > > > > > processors and as such some of the current resource structures > > > > > may not scale well for 64-bit remote processors, and would > > > > > require new versions of resource types. Each resource is currently > > > > > identified by a 32-bit type field. Introduce the concept of version > > > > > for these resource types by overloading this 32-bit type field > > > > > into two 16-bit version and type fields with the existing resources > > > > > behaving as version 0 thereby providing backward compatibility. > > > > > > > > > > The version field is passed as an additional argument to each of > > > > > the handler functions, and all the existing handlers are updated > > > > > accordingly. Each specific handler will be updated on a need basis > > > > > when a new version of the resource type is added. > > > > > > > > > > > > > I really would prefer that we add additional types for the new > > > > structures, neither side will be compatible with new versions without > > > > enhancements to their respective implementations anyways. > > > > > > OK. > > > > > > > > > > > > An alternate way would be to introduce the new types as completely > > > > > new resource types which would require additional customization of > > > > > the resource handlers based on the 32-bit or 64-bit mode of a remote > > > > > processor, and introduction of an additional mode flag to the rproc > > > > > structure. > > > > > > > > > > > > > What would this "mode" indicate? If it's version 0 or 1? > > > > > > No, for indicating if the remoteproc is 32-bit or 64-bit and adjust the > > > loading handlers if the resource types need to be segregated accordingly. > > > > > > > Sorry, I think I'm misunderstanding something. Wouldn't your 64-bit > > remote processor need different firmware from your 32-bit processor > > anyways, if you want to support the wider resource? And you would pack > > your firmware with the appropriate resource types? > > Yes, that's correct. > > > > > Afaict the bit width of your remote processor, busses or memory is > > unrelated to the choice of number of bits used to express things in the > > resource table. > > I would have to add the new resource type to the loading_handlers right, so > it is a question of whether we want to impose any restrictions in remoteproc > core or not from supporting a certain resource type (eg: I don't expect > RSC_TRACE entries on 64-bit processors). > Right, but either you add support for new resource types to the loading_handlers, or you add the version checks within each handler, either way you will have to do some work to be compatible with new versions. Regarding what resources would be fit for a 64-bit processor probably relates to many things, in particular the question of what we actually mean when we say that a coprocessor is 64-bit. So I don't really see a need for the remoteproc core to prevent someone to design their system/firmware to have a 64-bit CPU being passed 32-bit addresses. Regards, Bjorn
