Re: [PATCH v4 1/4] Documentation: fpga: dfl: Add documentation for DFHv1

[Ilpo Järvinen]

On Fri, 21 Oct 2022, Ilpo Järvinen wrote:

> On Thu, 20 Oct 2022, matthew.gerlach@xxxxxxxxxxxxxxx wrote:
> 
> > From: Matthew Gerlach <matthew.gerlach@xxxxxxxxxxxxxxx>
> > 
> > Add documentation describing the extensions provided by Version
> > 1 of the Device Feature Header (DFHv1).
> > 
> > Signed-off-by: Matthew Gerlach <matthew.gerlach@xxxxxxxxxxxxxxx>
> > ---
> > v4: Remove marketing speak and separate v0 and v1 descriptions.
> >     Fix errors reported by "make htmldocs".
> > 
> > v3: no change
> > 
> > v2: s/GUILD/GUID/
> >     add picture
> > ---
> >  Documentation/fpga/dfl.rst | 96 ++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 96 insertions(+)
> > 
> > diff --git a/Documentation/fpga/dfl.rst b/Documentation/fpga/dfl.rst
> > index 15b670926084..12365be435a8 100644
> > --- a/Documentation/fpga/dfl.rst
> > +++ b/Documentation/fpga/dfl.rst
> > @@ -561,6 +561,102 @@ new DFL feature via UIO direct access, its feature id should be added to the
> >  driver's id_table.
> >  
> >  
> > +Device Feature Header - Version 0
> > +===========================================
> > +The format of Version 0 of a Device Feature Header (DFH) is shown below::
> > +
> > +    +-----------------------------------------------------------------------+
> > +    |63 Type 60|59 DFH VER 52|51 Rsvd 41|40 EOL|39 Next 16|15 VER 12|11 ID 0| 0x00
> > +    +-----------------------------------------------------------------------+
> > +    |63                                 GUID_L                             0| 0x08
> > +    +-----------------------------------------------------------------------+
> > +    |63                                 GUID_H                             0| 0x10
> > +    +-----------------------------------------------------------------------+
> > +
> > +Offset 0x00
> > +Type - The type of DFH (e.g. FME, AFU, or private feature).
> > +DFH VER - The version of the DFH.
> > +Rsvd - Currently unused.
> > +EOL - Set if this DFH is the end of the Device Feature List (DFL).
> > +Next - The offset of the next DFH in the DFL from the start of the DFH.
> > +If EOL is set, Next refers to size of mmio for last feature in the list.
> > +ID - If Type field is 'private feature', then ID of the private feature.
> > +
> > +Offset 0x08
> > +GUID_L - Least significant 64 bits of a 128 bit Globally Unique Identifier
> > +if Type is FME or AFU.
> > +
> > +Offset 0x10
> > +GUID_H - Most significant 64 bits of a 128 bit Globally Unique Identifier
> > +if Type is FME or AFU.
> > +
> > +
> > +Device Feature Header - Version 1
> > +===========================================
> 
> While this is structurally better than the previous one. I'd still include
> at least one paragraph about the purpose. Something along these lines 
> (picked from v3 + edited the marketing speak/v0 compare away from it):
> 
> Version 1 of the Device Feature Header (DFHv1) provides flexibility and 
> extensibility to hardware designs using Device Feature Lists. It is a
> standardized mechanism for features to describe parameters/capabilities to 
> software.
> 
> With DFHv1:
> * GUID is mandatory for all types
> * The register space of the feature is decoupled from the location of the DFH
> * A list of parameter values associates to a particular feature.
> 
> After that, the header itself makes much more sense already.
> 
> > +The format of Version 1 of a Device Feature Header (DFH) is shown below::
> > +
> > +    +-----------------------------------------------------------------------+
> > +    |63 Type 60|59 DFH VER 52|51 Rsvd 41|40 EOL|39 Next 16|15 VER 12|11 ID 0| 0x00
> > +    +-----------------------------------------------------------------------+
> > +    |63                                 GUID_L                             0| 0x08
> > +    +-----------------------------------------------------------------------+
> > +    |63                                 GUID_H                             0| 0x10
> > +    +-----------------------------------------------------------------------+
> > +    |63                 Address/Offset                            1|  Rel  0| 0x18
> 
> Should this mention it's addr/offs of registers? As is it's bit hard to 
> figure out from the diagram w/o the extra description. I think you have 
> plenty of space for adding that extra bit of info.
> 
> > +    +-----------------------------------------------------------------------+
> > +    |63        Reg Size       32|Params 31|30 Group    16|15 Instance      0| 0x20
> > +    +-----------------------------------------------------------------------+
> > +    |63 Next      34|RSV33|EOP32|31 Param Version 16|15 Param ID           0| 0x28
> > +    +-----------------------------------------------------------------------+
> > +    |63                 Parameter Data                                     0| 0x30
> > +    +-----------------------------------------------------------------------+
> > +
> > +                                  ...
> > +
> > +    +-----------------------------------------------------------------------+
> > +    |63 Next parameter offset 32|31 Param Version 16|15 Param ID           0|

Copy-paste error on the next field.

-- 
 i.

> > +    +-----------------------------------------------------------------------+
> > +    |63                 Parameter Data                                     0|
> > +    +-----------------------------------------------------------------------+

> > +
> > +Offset 0x00
> > +Type - The type of DFH (e.g. FME, AFU, or private feature).
> > +DFH VER - The version of the DFH.
> > +Rsvd - Currently unused.
> > +EOL - Set if this DFH is the end of the Device Feature List (DFL).
> > +Next - The offset of the next DFH in the DFL from the start of the DFH.
> > +If EOL is set, Next refers to size of mmio for last feature in the list.
> > +ID - If Type field is 'private feature', then ID of the private feature.
> > +
> > +Offset 0x08
> > +GUID_L - Least significant 64 bits of a 128 bit Globally Unique Identifier.
> > +
> > +Offset 0x10
> > +GUID_H - Most significant 64 bits of a 128 bit Globally Unique Identifier
> > +if Type is FME or AFU.
> 
> A copy-paste error?
> 
> > +
> > +Offset 0x18
> > +Address/Offset - If Rel bit is set, then high 63 bits of a 16 bit aligned
> > +absolute address for the location of the feature's registers.
> > +If Rel bit is clear, then the feature's registers start at the
> > +offset from the start of the DFH.
> > +
> > +Offset 0x20
> > +Reg Size - Size of feature's register set.
> > +Params - Set if DFH has one or more parameter blocks.
> > +Group - Id of group if feature is part of a group.
> > +Instance - Id of instance of feature within a group.
> > +
> > +Offset 0x28 if feature has parameters
> > +Next - High 30 bits of a 32 bit aligned offset to the next parameter block.
> > +If EOP set, size of last parameter.
> > +Param Version - Version of Param ID.
> > +Param ID - ID of parameter.
> > +
> > +Offset 0x30
> > +Parameter Data - Parameter data whose size and format is defined by version
> > +and ID of the parameter.
> 
> I'd reverse the order and say "ID and version" (kind of major thing 
> first).
> 
> > +
> >  Open discussion
> >  ===============
> >  FME driver exports one ioctl (DFL_FPGA_FME_PORT_PR) for partial reconfiguration
> > 
> 
>