linux-kernel - Re: [PATCH v2 1/6] Documentation: fpga: dfl: Add documentation for DFHv1

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Date:   Tue, 27 Sep 2022 05:38:41 -0700 (PDT)
From:   matthew.gerlach@...ux.intel.com
To:     Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
cc:     hao.wu@...el.com, yilun.xu@...el.com, russell.h.weight@...el.com,
        basheer.ahmed.muddebihal@...el.com, trix@...hat.com,
        mdf@...nel.org, linux-fpga@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        tianfei.zhang@...el.com, corbet@....net,
        gregkh@...uxfoundation.org, linux-serial@...r.kernel.org,
        jirislaby@...nel.org, geert+renesas@...der.be,
        andriy.shevchenko@...ux.intel.com,
        niklas.soderlund+renesas@...natech.se, phil.edworthy@...esas.com,
        macro@...am.me.uk, johan@...nel.org, lukas@...ner.de
Subject: Re: [PATCH v2 1/6] Documentation: fpga: dfl: Add documentation for
 DFHv1



On Fri, 23 Sep 2022, Ilpo Järvinen wrote:

> On Fri, 23 Sep 2022, matthew.gerlach@...ux.intel.com wrote:
>
>> From: Matthew Gerlach <matthew.gerlach@...ux.intel.com>
>>
>> Add documentation describing the extensions provided by Version
>> 1 of the Device Feature Header (DFHv1).
>>
>> Signed-off-by: Matthew Gerlach <matthew.gerlach@...ux.intel.com>
>> ---
>> v2: s/GUILD/GUID/
>>     add picture
>> ---
>>  Documentation/fpga/dfl.rst | 49 ++++++++++++++++++++++++++++++++++++++
>>  1 file changed, 49 insertions(+)
>>
>> diff --git a/Documentation/fpga/dfl.rst b/Documentation/fpga/dfl.rst
>> index 15b670926084..7c786b75b498 100644
>> --- a/Documentation/fpga/dfl.rst
>> +++ b/Documentation/fpga/dfl.rst
>> @@ -561,6 +561,55 @@ new DFL feature via UIO direct access, its feature id should be added to the
>>  driver's id_table.
>>
>>
>> +Extending the Device Feature Header - DFHv1
>> +===========================================
>> +The current 8 bytes of the Device Feature Header, hereafter referred to as
>> +to DFHv0, provide very little opportunity for the hardware to describe itself
>> +to software. Version 1 of the Device Feature Header (DFHv1) is being introduced
>> +to provide increased flexibility and extensibility to hardware designs using
>> +Device Feature Lists.  The list below describes some of the goals behind the
>> +changes in DFHv1:
>> +
>> +* Provide a standardized mechanism for features to describe
>> +  parameters/capabilities to software.
>> +* Standardize the use of a GUID for all DFHv1 types.
>> +* Decouple the location of the DFH from the register space of the feature itself.
>> +
>> +Modeled after PCI Capabilities, DFHv1 Parameters provide a mechanism to associate
>> +a list of parameter values to a particular feature.
>> +
>> +With DFHv0, not all features types contained a GUID.  DFHv1 makes the GUID standard
>> +across all types.
>> +
>> +With DFHv0, the register map of a given feature is located immediately following
>> +the DFHv0 in the memory space.  With DFHv1, the location of the feature register
>> +map can be specified as an offset to the DFHv1 or as an absolute address.  The DFHv1
>> +structure is shown below:
>> +
>> +    +-----------------------------------------------------------------------+
>> +    |63 Type 60|59 DFH VER 52|51 Rsvd 41|40 EOL|39 Next 16|15 VER 12|11 ID 0|
>> +    +-----------------------------------------------------------------------+
>> +    |63                                 GUID_L                             0|
>> +    +-----------------------------------------------------------------------+
>> +    |63                                 GUID_H                             0|
>> +    +-----------------------------------------------------------------------+
>> +    |63                 Address/Offset                            1|  Rel  0|
>> +    +-----------------------------------------------------------------------+
>
> Is something missing here given the layout is claimed (in 2/6) to be:
>
> "DFHv1 Register Offset definitons
> In DHFv1, DFH + GUID + CSR_START + CSR_SIZE_GROUP + PARAM_HDR + PARAM_DATA"
>
> ?


I was hesitant to have a picture because the description would then be in 
two places.  I suspect my picture is not clear, but it does line up with 
the offset definitions:

DFH offset 0x0
GUID offsets 0x8 and 0x10
CSR_START offset 0x18
CSR_SIZE offset 0x20
First PARAM_HDR, if it exists, is 0x28,
First PARAM_DATA, if it exists, is 0x30.

>
>> +    |63 Size of register set  32|Params 31|30 Group    16|15 Instance      0|
>> +    +-----------------------------------------------------------------------+
>> +    |63 Next parameter offset 32|31 Param Version 16|15 Param ID           0|
>> +    +-----------------------------------------------------------------------+
>> +    |63                 Parameter Data                                     0|
>> +    +-----------------------------------------------------------------------+
>> +
>> +                                  ...
>> +
>> +    +-----------------------------------------------------------------------+
>> +    |63 Next parameter offset 32|31 Param Version 16|15 Param ID           0|
>> +    +-----------------------------------------------------------------------+
>> +    |63                 Parameter Data                                     0|
>> +    +-----------------------------------------------------------------------+
>> +
>>  Open discussion
>>  ===============
>>  FME driver exports one ioctl (DFL_FPGA_FME_PORT_PR) for partial reconfiguration
>>
>
> -- 
> i.
>
>