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

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Date:   Fri, 23 Sep 2022 17:34:11 +0300 (EEST)
From:   Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To:     Matthew Gerlach <matthew.gerlach@...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, 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"

?

> +    |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.