Documentation: fpga: dfl: Add documentation for DFHv1

Add documentation describing the extensions provided by Version
1 of the Device Feature Header (DFHv1).

Signed-off-by: Matthew Gerlach <matthew.gerlach@linux.intel.com>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Reviewed-by: Tom Rix <trix@redhat.com>
Link: https://lore.kernel.org/r/20230115151447.1353428-2-matthew.gerlach@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/fpga/dfl.rst

@@ -75,6 +75,125 @@ convenient for software to locate each feature by walking through this list,
 and can be implemented in register regions of any FPGA device.
 
 
+Device Feature Header - Version 0
+=================================
+Version 0 (DFHv0) is the original version of the Device Feature Header.
+All multi-byte quantities in DFHv0 are little-endian.
+The format of DFHv0 is shown below::
+
+    +-----------------------------------------------------------------------+
+    |63 Type 60|59 DFH VER 52|51 Rsvd 41|40 EOL|39 Next 16|15 REV 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 the DFH is the end of the Device Feature List (DFL).
+  * Next - The offset in bytes of the next DFH in the DFL from the DFH start,
+    and the start of a DFH must be aligned to an 8 byte boundary.
+    If EOL is set, Next is the size of MMIO of the last feature in the list.
+  * REV - The revision of the feature associated with this header.
+  * ID - The feature ID if Type is private feature.
+
+- Offset 0x08
+
+  * GUID_L - Least significant 64 bits of a 128-bit Globally Unique Identifier
+    (present only if Type is FME or AFU).
+
+- Offset 0x10
+
+  * GUID_H - Most significant 64 bits of a 128-bit Globally Unique Identifier
+    (present only if Type is FME or AFU).
+
+
+Device Feature Header - Version 1
+=================================
+Version 1 (DFHv1) of the Device Feature Header adds the following functionality:
+
+* Provides a standardized mechanism for features to describe
+  parameters/capabilities to software.
+* Standardize the use of a GUID for all DFHv1 types.
+* Decouples the DFH location from the register space of the feature itself.
+
+All multi-byte quantities in DFHv1 are little-endian.
+The format of Version 1 of the Device Feature Header (DFH) is shown below::
+
+    +-----------------------------------------------------------------------+
+    |63 Type 60|59 DFH VER 52|51 Rsvd 41|40 EOL|39 Next 16|15 REV 12|11 ID 0| 0x00
+    +-----------------------------------------------------------------------+
+    |63                                 GUID_L                             0| 0x08
+    +-----------------------------------------------------------------------+
+    |63                                 GUID_H                             0| 0x10
+    +-----------------------------------------------------------------------+
+    |63                   Reg Address/Offset                      1|  Rel  0| 0x18
+    +-----------------------------------------------------------------------+
+    |63        Reg Size       32|Params 31|30 Group    16|15 Instance      0| 0x20
+    +-----------------------------------------------------------------------+
+    |63 Next    35|34RSV33|EOP32|31 Param Version 16|15 Param ID           0| 0x28
+    +-----------------------------------------------------------------------+
+    |63                 Parameter Data                                     0| 0x30
+    +-----------------------------------------------------------------------+
+
+                                  ...
+
+    +-----------------------------------------------------------------------+
+    |63 Next    35|34RSV33|EOP32|31 Param Version 16|15 Param ID           0|
+    +-----------------------------------------------------------------------+
+    |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 the DFH is the end of the Device Feature List (DFL).
+  * Next - The offset in bytes of the next DFH in the DFL from the DFH start,
+    and the start of a DFH must be aligned to an 8 byte boundary.
+    If EOL is set, Next is the size of MMIO of the last feature in the list.
+  * REV - The revision of the feature associated with this header.
+  * ID - The feature ID if Type is 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.
+
+- Offset 0x18
+
+  * Reg Address/Offset - If Rel bit is set, then the value is the high 63 bits
+    of a 16-bit aligned absolute address of the feature's registers. Otherwise
+    the value is the offset from the start of the DFH of the feature's registers.
+
+- Offset 0x20
+
+  * Reg Size - Size of feature's register set in bytes.
+  * Params - Set if DFH has a list of parameter blocks.
+  * Group - Id of group if feature is part of a group.
+  * Instance - Id of feature instance within a group.
+
+- Offset 0x28 if feature has parameters
+
+  * Next - Offset to the next parameter block in 8 byte words. If EOP set,
+    size in 8 byte words 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.
+
+
 FIU - FME (FPGA Management Engine)
 ==================================
 The FPGA Management Engine performs reconfiguration and other infrastructure