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SubjectRe: [PATCH 2/4] remoteproc: introduce version element into resource type field
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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@ti.com>
>> ---
>> 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

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