linux-kernel - Re: [PATCH v4 5/5] usb: dwc3: rockchip: add devicetree bindings documentation

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Date:	Fri, 17 Jun 2016 01:15:35 +0200
From:	Heiko Stübner <heiko@...ech.de>
To:	William Wu <william.wu@...k-chips.com>
Cc:	gregkh@...uxfoundation.org, balbi@...nel.org,
	linux-rockchip@...ts.infradead.org, briannorris@...gle.com,
	dianders@...gle.com, kever.yang@...k-chips.com,
	huangtao@...k-chips.com, frank.wang@...k-chips.com,
	eddie.cai@...k-chips.com, John.Youn@...opsys.com,
	linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
	sergei.shtylyov@...entembedded.com
Subject: Re: [PATCH v4 5/5] usb: dwc3: rockchip: add devicetree bindings documentation

Hi William,

Am Donnerstag, 2. Juni 2016, 20:34:56 schrieb William Wu:
> This patch adds the devicetree documentation required for Rockchip
> USB3.0 core wrapper consisting of USB3.0 IP from Synopsys.
> 
> It supports DRD mode, and could operate in device mode (SS, HS, FS)
> and host mode (SS, HS, FS, LS).
> 
> Signed-off-by: William Wu <william.wu@...k-chips.com>

devicetree binding documentation patches should include the devicetree 
maintainers (scripts/get_maintainer.pl)

> ---
> Changes in v4:
> - modify commit log, and add phy documentation location (Sergei)
> 
> Changes in v3:
> - add dwc3 address (balbi)
> 
> Changes in v2:
> - add rockchip,dwc3.txt to Documentation/devicetree/bindings/ (balbi, 
Brian)
> 
>  .../devicetree/bindings/usb/rockchip,dwc3.txt      | 46
> ++++++++++++++++++++++ 1 file changed, 46 insertions(+)
>  create mode 100644 
Documentation/devicetree/bindings/usb/rockchip,dwc3.txt
> 
> diff --git a/Documentation/devicetree/bindings/usb/rockchip,dwc3.txt
> b/Documentation/devicetree/bindings/usb/rockchip,dwc3.txt new file mode
> 100644
> index 0000000..0edf013
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/usb/rockchip,dwc3.txt
> @@ -0,0 +1,46 @@
> +Rockchip SuperSpeed DWC3 USB SoC controller
> +
> +Required properties:
> +- compatible:	should contain "rockchip,dwc3"

are you sure this will work for all future socs in the same way? I guess 
doing this as rockchip,rk3399-dwc3 might make our lifes easier down the road 
:-) [both the xilinx and st dwc3 bindings do already that]

> +- clocks:		A list of phandle + clock-specifier pairs for the
> +				clocks listed in clock-names
> +- clock-names:	Should contain the following:
> +  "clk_usb3otg0_ref"	Controller reference clk
> +  "clk_usb3otg0_suspend"Controller suspend clk, can use 24 MHz or 32 KHz
> +  "aclk_usb3"		Master/Core clock, have to be >= 62.5 MHz for SS 
operation

clock names should always be in the scope of the device block (named after 
what it supplies). And looking at the dwc3-xilinx.txt binding, I'd suggest 
getting inspiration from their clock names (bus_clk, ref_clk, suspend_clk or 
so)

> +Optional clocks:
> +  "aclk_usb3otg0"	Aclk for specific usb controller clock.
> +  "aclk_usb3_rksoc_axi_perf"  USB AXI perf clock.  Not present on all
> platforms. 

The clock names looks pretty strange. What are they for? Especially as 
nothing seems to use them right now.


> +  "aclk_usb3_grf"	USB grf clock.  Not present on all platforms.

for my own education, which part of the GRF does this clock supply?


> +
> +Required child node:
> +A child node must exist to represent the core DWC3 IP block. The name of
> +the node is not important. The content of the node is defined in dwc3.txt.
> +
> +Phy documentation is provided in the following places:
> +Documentation/devicetree/bindings/phy/rockchip,dwc3-usb-phy.txt
> +
> +Example device nodes:
> +
> +	usbdrd3_0: usb@...00000 {
> +		compatible = "rockchip,dwc3";
> +		clocks = <&cru SCLK_USB3OTG0_REF>, <&cru SCLK_USB3OTG0_SUSPEND>,
> +			 <&cru ACLK_USB3>, <&cru ACLK_USB3OTG0>,
> +			 <&cru ACLK_USB3_RKSOC_AXI_PERF>, <&cru ACLK_USB3_GRF>;
> +		clock-names = "clk_usb3otg0_ref", "clk_usb3otg0_suspend",
> +			      "aclk_usb3", "aclk_usb3otg0",
> +			      "aclk_usb3_rksoc_axi_perf", "aclk_usb3_grf";
> +		#address-cells = <2>;
> +		#size-cells = <2>;
> +		ranges;
> +		status = "disabled";
> +		usbdrd_dwc3_0: dwc3@...00000 {
> +			compatible = "snps,dwc3";
> +			reg = <0x0 0xfe800000 0x0 0x100000>;
> +			interrupts = <GIC_SPI 105 IRQ_TYPE_LEVEL_HIGH>;
> +			dr_mode = "otg";
> +			status = "disabled";
> +		};
> +	};