USB support for device tree

[Pavan Kondeti]

Hi

On 11/4/2011 10:15 PM, Grant Likely wrote:
> On Fri, Nov 4, 2011 at 4:25 AM, Pavan Kondeti <pkondeti at codeaurora.org> wrote:
>> Hi
>>
>> I am working on adding USB device tree support for MSM platform.  One of
>> our chip set has 2 hsusb cores. The first core is configured as otg and
>> the other core is configured in host only mode (EHCI compliant). Are the
>> below device node names Okay? Please suggest.
>>
>> hsusb0-otg: usb at 0xa6000000 {
>>        compatible = "qcom,hsusb-otg";
>>        ---
>> };
>>
>> hsusb0-device: usb at 0xa6000000 {
>>        compatible = "qcom,hsusb-device";
>>        ---
>> };
>>
>> hsusb0-host: usb at 0xa6000000 {
>>        compatible = "qcom,hsusb-host", "usb-ehci";
>>        ---
>> };
>>
>> hsusb1-host: usb at 0xa6000000 {
>>        compatible = "qcom,hsusb-host", "usb-ehci";
>>        ---
>> };
>>
>> /* super speed support
>>
>> ssusb0-device: usb at 0xa6000000 {
>>        compatible = "qcom,ssusb-device";
>> };
> 
> 
> The host controller node names as "usb@<adddr>" as you have here is
> exactly right.  The driver doesn't care and will only look at the
> compatible list.  OTG controllers can also use "usb@" as the prefix.
> 
> Controllers that are only in device mode should probably be called
> something like "usb-gadget@<addr>" or similar, because "usb@" is used
> for host controllers.
> 

In our case OTG, gadget and host controllers are part of a single core
i.e they all share the same register address space.

If I use usb at addr for OTG controller, then host and OTG device node
names becomes same. Is that okay? Can two devices have the same device
node name in device tree source file?

> The label names (hsusb*-host, hsusb*-device) are completely irrelevant
> since Linux never sees them.  Use whatever you want for the label
> names.
> 
Is it a good practice to give label names? I thought, it improves a bit
readability of device tree source file.

> Also, the form of the node name is: "usb at a6000000" (without '0x' in
> the address).
> 
Thanks for the correction.

Thanks,
Pavan


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