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Date:   Thu, 28 Mar 2019 13:07:59 -0500
From:   Rob Herring <robh@...nel.org>
To:     Kishon Vijay Abraham I <kishon@...com>
Cc:     Roger Quadros <rogerq@...com>, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH v3 3/5] dt-bindings: phy: ti: Add dt binding
 documentation for SERDES in AM654x SoC

On Mon, Mar 25, 2019 at 01:38:13PM +0530, Kishon Vijay Abraham I wrote:
> AM654x has two SERDES instances. Each instance has three input clocks
> (left input, externel reference clock and right input) and two output
> clocks (left output and right output) in addition to a PLL mux clock
> which the SERDES uses for Clock Multiplier Unit (CMU refclock).
> The PLL mux clock can select from one of the three input clocks.
> The right output can select between left input and external reference
> clock while the left output can select between the right input and
> external reference clock.
> 
> The left and right input reference clock of SERDES0 and SERDES1
> respectively are connected to the SoC clock. In the case of two lane
> SERDES personality card, the left input of SERDES1 is connected to
> the right output of SERDES0 in a chained fashion.
> 
> See section "Reference Clock Distribution" of AM65x Sitara Processors
> TRM (SPRUID7 – April 2018) for more details.
> 
> Add dt-binding documentation in order to represent all these different
> configurations in device tree.
> 
> Signed-off-by: Kishon Vijay Abraham I <kishon@...com>
> ---
>  .../bindings/phy/ti,phy-am654-serdes.txt      | 81 +++++++++++++++++++
>  include/dt-bindings/phy/phy-am654-serdes.h    | 13 +++
>  2 files changed, 94 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/phy/ti,phy-am654-serdes.txt
>  create mode 100644 include/dt-bindings/phy/phy-am654-serdes.h
> 
> diff --git a/Documentation/devicetree/bindings/phy/ti,phy-am654-serdes.txt b/Documentation/devicetree/bindings/phy/ti,phy-am654-serdes.txt
> new file mode 100644
> index 000000000000..25a9206147ad
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/phy/ti,phy-am654-serdes.txt
> @@ -0,0 +1,81 @@
> +TI AM654 SERDES
> +
> +Required properties:
> + - compatible: Should be "ti,phy-am654-serdes"
> + - reg : Address and length of the register set for the device.
> + - reg-names: Should be "serdes" which corresponds to the register space
> +	populated in "reg".

*-names is kind of pointless with only 1 entry.

> + - #phy-cells: determine the number of cells that should be given in the
> +	phandle while referencing this phy. Should be "2". The 1st cell
> +	corresponds to the phy type (should be one of the types specified in
> +	include/dt-bindings/phy/phy.h) and the 2nd cell should be the serdes
> +	lane function.
> +	If SERDES0 is referenced 2nd cell should be:
> +		0 - USB3
> +		1 - PCIe0 Lane0
> +		2 - ICSS2 SGMII Lane0
> +	If SERDES1 is referenced 2nd cell should be:
> +		0 - PCIe1 Lane0
> +		1 - PCIe0 Lane1
> +		2 - ICSS2 SGMII Lane1
> + - clocks: List of clock-specifiers representing the input to the SERDES.
> +	Should have 3 items representing the left input clock, external
> +	reference clock and right input clock in that order.
> + - clock-output-names: List of clock names for each of the clock outputs of
> +	SERDES. Should have 3 items for CMU reference clock,
> +	left output clock and right output clock in that order.
> + - assigned-clocks: As defined in
> +	Documentation/devicetree/bindings/clock/clock-bindings.txt
> + - assigned-clock-parents: As defined in
> +	Documentation/devicetree/bindings/clock/clock-bindings.txt
> + - #clock-cells: Should be <1> to choose between the 3 output clocks.
> +	Defined in Documentation/devicetree/bindings/clock/clock-bindings.txt
> +
> +   The following macros are defined in dt-bindings/phy/phy-am654-serdes.h
> +   for selecting the correct reference clock. This can be used while
> +   specifying the clocks created by SERDES.
> +	=> AM654_SERDES_CMU_REFCLK
> +	=> AM654_SERDES_LO_REFCLK
> +	=> AM654_SERDES_RO_REFCLK
> +
> + - mux-controls: phandle to the multiplexer

What does this mux?

> +
> +Example:
> +
> +Example for SERDES0 is given below. It has 3 clock inputs;
> +left input reference clock as indicated by <&k3_clks 153 4>, external
> +reference clock as indicated by <&k3_clks 153 1> and right input
> +reference clock as indicated by <&serdes1 AM654_SERDES_LO_REFCLK>. (The
> +right input of SERDES0 is connected to the left output of SERDES1).
> +
> +SERDES0 registers 3 clock outputs as indicated in clock-output-names. The
> +first refers to the CMU reference clock, second refers to the left output
> +reference clock and the third refers to the right output reference clock.
> +
> +The assigned-clocks and assigned-clock-parents is used here to set the
> +parent of left input reference clock to MAINHSDIV_CLKOUT4 and parent of
> +CMU reference clock to left input reference clock.
> +
> +serdes0: serdes@...000 {
> +	compatible = "ti,phy-am654-serdes";
> +	reg = <0x0 0x900000 0x0 0x2000>;
> +	reg-names = "serdes";

> +	#phy-cells = <2>;
> +	power-domains = <&k3_pds 153>;

Not documented.

> +	clocks = <&k3_clks 153 4>, <&k3_clks 153 1>,
> +			<&serdes1 AM654_SERDES_LO_REFCLK>;
> +	clock-output-names = "serdes0_cmu_refclk", "serdes0_lo_refclk",
> +				"serdes0_ro_refclk";
> +	assigned-clocks = <&k3_clks 153 4>, <&serdes0 AM654_SERDES_CMU_REFCLK>;
> +	assigned-clock-parents = <&k3_clks 153 8>, <&k3_clks 153 4>;
> +	ti,serdes-clk = <&serdes0_clk>;
> +	mux-controls = <&serdes_mux 0>;
> +	#clock-cells = <1>;
> +};
> +
> +Example for PCIe consumer node using the SERDES PHY specifier is given below.
> +&pcie0_rc {
> +        num-lanes = <2>;
> +        phys = <&serdes0 PHY_TYPE_PCIE 1>, <&serdes1 PHY_TYPE_PCIE 1>;
> +        phy-names = "pcie-phy0", "pcie-phy1";
> +};
> diff --git a/include/dt-bindings/phy/phy-am654-serdes.h b/include/dt-bindings/phy/phy-am654-serdes.h
> new file mode 100644
> index 000000000000..e8d901729ed9
> --- /dev/null
> +++ b/include/dt-bindings/phy/phy-am654-serdes.h
> @@ -0,0 +1,13 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * This header provides constants for AM654 SERDES.
> + */
> +
> +#ifndef _DT_BINDINGS_AM654_SERDES
> +#define _DT_BINDINGS_AM654_SERDES
> +
> +#define AM654_SERDES_CMU_REFCLK	0
> +#define AM654_SERDES_LO_REFCLK	1
> +#define AM654_SERDES_RO_REFCLK	2
> +
> +#endif /* _DT_BINDINGS_AM654_SERDES */
> -- 
> 2.17.1
> 

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