RE: [PATCH V3 01/12] dt-bindings: xilinx-sdfec: Add SDFEC binding

[Dragan Cvetic]

Hi Rob,

Please find inline comments below

Regards
Dragan

> -----Original Message-----
> From: Rob Herring [mailto:robh@xxxxxxxxxx]
> Sent: Thursday 2 May 2019 21:16
> To: Dragan Cvetic <draganc@xxxxxxxxxx>
> Cc: arnd@xxxxxxxx; gregkh@xxxxxxxxxxxxxxxxxxx; Michal Simek <michals@xxxxxxxxxx>; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx;
> mark.rutland@xxxxxxx; devicetree@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Derek Kiernan <dkiernan@xxxxxxxxxx>
> Subject: Re: [PATCH V3 01/12] dt-bindings: xilinx-sdfec: Add SDFEC binding
> 
> On Thu, May 2, 2019 at 6:04 AM Dragan Cvetic <draganc@xxxxxxxxxx> wrote:
> >
> > Hi Rob,
> >
> > Please find my inline comments below
> >
> > Thank you
> > Dragan
> >
> > > -----Original Message-----
> > > From: Rob Herring [mailto:robh@xxxxxxxxxx]
> > > Sent: Wednesday 1 May 2019 20:48
> > > To: Dragan Cvetic <draganc@xxxxxxxxxx>
> > > Cc: arnd@xxxxxxxx; gregkh@xxxxxxxxxxxxxxxxxxx; Michal Simek <michals@xxxxxxxxxx>; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx;
> > > mark.rutland@xxxxxxx; devicetree@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Derek Kiernan <dkiernan@xxxxxxxxxx>
> > > Subject: Re: [PATCH V3 01/12] dt-bindings: xilinx-sdfec: Add SDFEC binding
> > >
> > > On Sat, Apr 27, 2019 at 11:04:55PM +0100, Dragan Cvetic wrote:
> > > > Add the Soft Decision Forward Error Correction (SDFEC) Engine
> > > > bindings which is available for the Zynq UltraScale+ RFSoC
> > > > FPGA's.
> > > >
> > > > Signed-off-by: Dragan Cvetic <dragan.cvetic@xxxxxxxxxx>
> > > > Signed-off-by: Derek Kiernan <derek.kiernan@xxxxxxxxxx>
> > > > ---
> > > >  .../devicetree/bindings/misc/xlnx,sd-fec.txt       | 58 ++++++++++++++++++++++
> > > >  1 file changed, 58 insertions(+)
> > > >  create mode 100644 Documentation/devicetree/bindings/misc/xlnx,sd-fec.txt
> > > >
> > > > diff --git a/Documentation/devicetree/bindings/misc/xlnx,sd-fec.txt b/Documentation/devicetree/bindings/misc/xlnx,sd-
> fec.txt
> > > > new file mode 100644
> > > > index 0000000..425b6a6
> > > > --- /dev/null
> > > > +++ b/Documentation/devicetree/bindings/misc/xlnx,sd-fec.txt
> > > > @@ -0,0 +1,58 @@
> > > > +* Xilinx SDFEC(16nm) IP *
> > > > +
> > > > +The Soft Decision Forward Error Correction (SDFEC) Engine is a Hard IP block
> > > > +which provides high-throughput LDPC and Turbo Code implementations.
> > > > +The LDPC decode & encode functionality is capable of covering a range of
> > > > +customer specified Quasi-cyclic (QC) codes. The Turbo decode functionality
> > > > +principally covers codes used by LTE. The FEC Engine offers significant
> > > > +power and area savings versus implementations done in the FPGA fabric.
> > > > +
> > > > +
> > > > +Required properties:
> > > > +- compatible: Must be "xlnx,sd-fec-1.1"
> > > > +- clock-names : List of input clock names from the following:
> > > > +    - "core_clk", Main processing clock for processing core (required)
> > > > +    - "s_axi_aclk", AXI4-Lite memory-mapped slave interface clock (required)
> > > > +    - "s_axis_din_aclk", DIN AXI4-Stream Slave interface clock (optional)
> > > > +    - "s_axis_din_words-aclk", DIN_WORDS AXI4-Stream Slave interface clock (optional)
> > > > +    - "s_axis_ctrl_aclk",  Control input AXI4-Stream Slave interface clock (optional)
> > > > +    - "m_axis_dout_aclk", DOUT AXI4-Stream Master interface clock (optional)
> > > > +    - "m_axis_dout_words_aclk", DOUT_WORDS AXI4-Stream Master interface clock (optional)
> > > > +    - "m_axis_status_aclk", Status output AXI4-Stream Master interface clock (optional)
> > > > +- clocks : Clock phandles (see clock_bindings.txt for details).
> > > > +- reg: Should contain Xilinx SDFEC 16nm Hardened IP block registers
> > > > +  location and length.
> > > > +- xlnx,sdfec-code : Should contain "ldpc" or "turbo" to describe the codes
> > > > +  being used.
> > > > +- xlnx,sdfec-din-words : A value 0 indicates that the DIN_WORDS interface is
> > > > +  driven with a fixed value and is not present on the device, a value of 1
> > > > +  configures the DIN_WORDS to be block based, while a value of 2 configures the
> > > > +  DIN_WORDS input to be supplied for each AXI transaction.
> > > > +- xlnx,sdfec-din-width : Configures the DIN AXI stream where a value of 1
> > > > +  configures a width of "1x128b", 2 a width of "2x128b" and 4 configures a width
> > > > +  of "4x128b".
> > >
> > > Perhaps append with '-bits' and make the values 0, 128, 256, 512.
> > >
> >
> >
> > The suggested will require the extra code for converting from 128,256,512  to 1,2,4, as HW is configured with 1, 2 and 4.
> 
> A simple divide by 128.
> 
> We generally prefer DT to use real units rather than register values.

The data enters/exits SDFEC in 128 bits word units (__int128).
1,2,4 are not a register values only, they represent a number
of units which are used in SDFEC communication.

> 
> Rob