Re: [PATCH 2/4] remoteproc: introduce version element into resource type field

[Suman Anna]

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.

> > Signed-off-by: Suman Anna <s-anna@xxxxxx>
> > ---
> >   drivers/remoteproc/remoteproc_core.c    | 25 +++++++++++++++----------
> >   drivers/remoteproc/remoteproc_debugfs.c | 17 ++++++++++-------
> >   include/linux/remoteproc.h              |  8 +++++++-
> >   3 files changed, 32 insertions(+), 18 deletions(-)
> [..]
> > diff --git a/include/linux/remoteproc.h b/include/linux/remoteproc.h
> > index 77788a4bb94e..526d3cb45e37 100644
> > --- a/include/linux/remoteproc.h
> > +++ b/include/linux/remoteproc.h
> > @@ -86,7 +86,13 @@ struct resource_table {
> >    * this header, and it should be parsed according to the resource type.
> >    */
> >   struct fw_rsc_hdr {
> > -	u32 type;
> > +	union {
> > +		u32 type;
> > +		struct {
> > +			u16 t;
> > +			u16 v;
> > +		} st;
>
> I see your "type" is little endian...

Yeah, definitely a draw-back if we want to support big-endian rprocs. Do 
you have any remoteprocs following big-endian? All TI remoteprocs are 
little-endian except for really old ones.

regards
Suman