linux-kernel - Re: [PATCH v2 5/5] usb: dwc3: rockchip: add devicetree bindings documentation

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Date:	Wed, 25 May 2016 16:58:38 +0800
From:	William Wu <william.wu@...k-chips.com>
To:	Felipe Balbi <balbi@...nel.org>, gregkh@...uxfoundation.org,
	heiko@...ech.de, Rob Herring <robh+dt@...nel.org>
CC:	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,
	devicetree@...r.kernel.org
Subject: Re: [PATCH v2 5/5] usb: dwc3: rockchip: add devicetree bindings documentation

Hi Felipe & Rob,
On 05/25/2016 04:04 PM, Felipe Balbi wrote:
> Hi,
>
> William Wu <william.wu@...k-chips.com> writes:
>> Hi Felipe,
>>
>> On 05/24/2016 05:32 PM, Felipe Balbi wrote:
>>> Hi,
>>>
>>> William Wu <william.wu@...k-chips.com> writes:
>>>> This patch documents the device tree documentation required for
>>>> Rockchip USB3.0 core wrapper consist of USB3.0 IP from Synopsys.
>>>>
>>>> It 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>
>>>> ---
>>>> Changes in v2:
>>>> - add rockchip,dwc3.txt to Documentation/devicetree/bindings/ (Felipe, Brian)
>>>>
>>>>    .../devicetree/bindings/usb/rockchip,dwc3.txt      | 45 ++++++++++++++++++++++
>>>>    1 file changed, 45 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..10303d9
>>>> --- /dev/null
>>>> +++ b/Documentation/devicetree/bindings/usb/rockchip,dwc3.txt
>>>> @@ -0,0 +1,45 @@
>>>> +Rockchip SuperSpeed DWC3 USB SoC controller
>>>> +
>>>> +Required properties:
>>>> +- compatible:	should contain "rockchip,dwc3"
>>>> +- 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
>>>> +
>>>> +
>>>> +Optional clocks:
>>>> +  "aclk_usb3otg0"	Aclk for specific usb controller clock.
>>>> +  "aclk_usb3_rksoc_axi_perf"  USB AXI perf clock.  Not present on all platforms.
>>>> +  "aclk_usb3_grf"	USB grf clock.  Not present on all platforms.
>>>> +
>>>> +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:
>>>> +
>>>> +Example device nodes:
>>>> +
>>>> +	usbdrd3_0: usb@...00000 {
>>>> +
>>> no reg property?
>> For now, we don't need reg property here. Because we only need to do
>> enable some clocks and populate its children in
>> drivers/usb/dwc3/dwc3-of-simple.c.
>> And it's similar to arch/arm/boot/dts/exynos5420.dtsi usbdrd3_0 node.
>>> 		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 {
>>> no address here?
>> I think here don't  necessarily need address. The child node dwc3 can
>> inherit address from the parent node.
>> And with this dtsi patch, the dev path show as follows:
>> /sys/devices/platform/usb@...00000/fe800000.dwc3
>>
>> Is it need for coding style or other reason?
> I don't think your arguments match what devicetree folks want to see in
> DT. Let's ask them. Rob, care to look at this one?
Sorry, I need to correct myself. I have done some test, and the result 
shows that
the  child node dwc3 don't inherit address from the parent node, but get 
address
from its reg property. And It seems that whether I add address here or 
not, the
dwc3 node always get address from reg property.
However, I don't know much about the DT. But I think it's better to add 
address here than no.
>
>>>> +			compatible = "snps,dwc3";
>>>> +			reg = <0x0 0xfe800000 0x0 0x100000>;
>>>> +			interrupts = <GIC_SPI 105 IRQ_TYPE_LEVEL_HIGH>;
>>>> +			dr_mode = "otg";
>>>> +			status = "disabled";
>>>> +		};
>>>> +	};
>>>> -- 
>>>> 1.9.1
>>>>
>>>>
>>>> --
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>>
>> --
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