Re: [PATCH 1/3] dt-bindings: can: xilinx_can: add Xilinx CAN FD bindings

[Rob Herring <robh@kernel.org>]

On Wed, Jun 27, 2018 at 05:34:12PM +0300, Anssi Hannula wrote:
> Add compatible string and new attributes to support the Xilinx CAN FD
> core.
> 
> Unlike the previously documented Xilinx CAN cores, the CAN FD core has
> TX mailboxes instead of TX FIFO, and optionally RX mailboxes instead of
> RX FIFO (selected at core generation time, not switchable at runtime).
> Add "tx-mailbox-count" and "rx-mailbox-count" to specify the mailbox
> counts instead of reusing "tx-fifo-depth" and "rx-fifo-depth". "rx-mode"
> attribute is added to allow mailbox mode.
> 
> The RX FIFO depth is constant 32, but allow it to be specified via
> "rx-fifo-depth" to match DT usage with Zynq CAN (which has constant RX
> FIFO of depth of 64).
> 
> Signed-off-by: Anssi Hannula <anssi.hannula@bitwise.fi>
> Cc: Michal Simek <michal.simek@xilinx.com>
> 
> ---
> 
> Xilinx has an out-of-tree driver that uses the same compatible string
> "xlnx,canfd-1.0" but reads the TX mailbox count from "tx-fifo-depth"
> and always assumes RX FIFO mode.
> 
> I'm not 100% sure if we want to introduce "tx-mailbox-count" and
> "rx-mailbox-count" or just do the same and use the "fifo" depth
> properties for non-fifo as well.

Don't you need a way to distinguish between rx fifo and mailbox?

> 
> 
>  .../devicetree/bindings/net/can/xilinx_can.txt     | 36 +++++++++++++++++-----
>  1 file changed, 28 insertions(+), 8 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/net/can/xilinx_can.txt b/Documentation/devicetree/bindings/net/can/xilinx_can.txt
> index fe38847..ab14e56 100644
> --- a/Documentation/devicetree/bindings/net/can/xilinx_can.txt
> +++ b/Documentation/devicetree/bindings/net/can/xilinx_can.txt
> @@ -2,20 +2,28 @@ Xilinx Axi CAN/Zynq CANPS controller Device Tree Bindings
>  ---------------------------------------------------------
>  
>  Required properties:
> -- compatible		: Should be "xlnx,zynq-can-1.0" for Zynq CAN
> -			  controllers and "xlnx,axi-can-1.00.a" for Axi CAN
> -			  controllers.
> -- reg			: Physical base address and size of the Axi CAN/Zynq
> -			  CANPS registers map.
> +- compatible		: Should be:
> +			  - "xlnx,zynq-can-1.0" for Zynq CAN controllers
> +			  - "xlnx,axi-can-1.00.a" for Axi CAN controllers
> +			  - "xlnx,canfd-1.0" for CAN FD controllers
> +- reg			: Physical base address and size of the controller
> +			  registers map.
>  - interrupts		: Property with a value describing the interrupt
>  			  number.
>  - interrupt-parent	: Must be core interrupt controller
>  - clock-names		: List of input clock names - "can_clk", "pclk"
> -			  (For CANPS), "can_clk" , "s_axi_aclk"(For AXI CAN)
> +			  (For CANPS), "can_clk", "s_axi_aclk" (For AXI CAN

"(For CANPS)" should go on the previous line to be more readable.

> +		          and CAN FD)
>  			  (See clock bindings for details).
>  - clocks		: Clock phandles (see clock bindings for details).
> -- tx-fifo-depth		: Can Tx fifo depth.
> -- rx-fifo-depth		: Can Rx fifo depth.
> +- rx-mode		: Rx mode of a CAN FD controller core: "sequential"
> +			  (fifo) or "mailbox" (default: "sequential").

You can determine this with the presence of the below properties.

> +- tx-fifo-depth		: Can Tx fifo depth (Zynq, Axi CAN).
> +- rx-fifo-depth		: Can Rx fifo depth (Zynq, Axi CAN, CAN FD in
> +                          sequential Rx mode).
> +- tx-mailbox-count	: Can Tx mailbox buffer count (CAN FD).
> +- rx-mailbox-count	: Can Rx mailbox buffer count (CAN FD in mailbox Rx
> +			  mode).
>  
>  
>  Example:
> @@ -42,3 +50,15 @@ For Axi CAN Dts file:
>  			tx-fifo-depth = <0x40>;
>  			rx-fifo-depth = <0x40>;
>  		};
> +For CAN FD Dts file:
> +	canfd_0: canfd@40000000 {
> +			compatible = "xlnx,canfd-1.0";
> +			clocks = <&clkc 0>, <&clkc 1>;
> +			clock-names = "can_clk", "s_axi_aclk";
> +			reg = <0x40000000 0x2000>;
> +			interrupt-parent = <&intc>;
> +			interrupts = <0 59 1>;
> +			rx-mode = "sequential";
> +			tx-mailbox-count = <0x20>;
> +			rx-fifo-depth = <0x20>;
> +		};
> -- 
> 2.8.3
>