[U-Boot] [PATCH v4 2/4] USB: host: Add the USB3 host driver

Mon Sep 9 11:33:43 UTC 2019

Hi Sherry,

On 03/09/2019 14:44, Sherry Sun wrote:
> Hi Jean,
>
>>
>> On 02/09/2019 13:29, Sherry Sun wrote:
>>> Hi Vignesh,
>>>
>>>> Hi Sherry,
>>>>
>>>> [...]
>>>>>> AFAIK, U-Boot does not support runtime switching of USB port to
>>>>>> host from device and vice versa. This is the case for existing
>>>>>> driver like
>>>> DWC3/MUSB etc.
>>>>>> Ideally we would need a role switch driver that unbinds and rebinds
>>>>>> host vs device driver as when required based on U-Boot cmd or via
>>>>>> an API (if required to be done during SPL stage etc).
>>>>> I wonder if we can add two subnodes under the wrapper node as below,
>>>> one bind to usb gadget driver and another bind to usb host driver.
>>>>> So if we want to use usb device, just call the gadget driver, and if
>>>>> want to
>>>> use usb host, just call the host driver. The driver will probe correspond
>> node.
>>>>> I'm not sure if it is feasible, what do you think about it?
>>>>>
>>>>>         usbss0: cdns_usb at 4104000 {
>>>>>             compatible = "ti,j721e-usb";
>>>>>             [....]
>>>>>             usb0: usb at 6010000 {		/* xhci reg address*/
>>>>>                 compatible = "cdns,usb3-1.0.1";
>>>>> 	dr_mode = "host";
>>>>> 	[....]
>>>>> 	}
>>>>>             usb1: usb at 6020000 {		/* dev reg address*/
>>>>>                 compatible = "cdns,usb3-1.0.1";
>>>>> 	dr_mode = "peripheral";
>>>>> 	[....]
>>>>> 	}
>>>>>       }
>>>>>
>>>> But this is not how DT would look in kernel. There will be single DT
>>>> node representing both Host and Device node. DT repesentation should
>>>> not be changed based on OS/bootloader, its HW description and must
>> remain same.
>>>> Unbinding host/gadget driver and rebinding with a different role
>>>> should not be hard as the U-Boot core infrastructure exists.
>>>>
>>>> Moreover if xhci reg and dev reg are separated into different nodes
>>>> dont we still need access to OTG register block to switch b/w host and
>> device mode?
>>> I think we may not need to access OTG register if we add two subnodes for
>> gadget and host.
>>> But I see a for loop in dwc3_glue_bind() as follows, if there only one single
>> node representing both Host and Device node under usb wrapper node, why
>> we need this for loop?
>>> 212     for (node = fdt_first_subnode(fdt, dev_of_offset(parent)); node > 0;
>>> 213          node = fdt_next_subnode(fdt, node)) {
>> I believe this is a legacy from the code it was inspired from.
>>
>> Indeed the loop is not required.
>>
>> Like Vignesh I think we must stick with the dt-bindings used by the kernel.
> Thanks for your reply, I understand now.
>
>> BTW we are working on the USB3 support right now that is lacking in our tree.
>> I choose to keep the PHY drivers as close as possible to their linux version. I'll
>> probably start posting preliminary patches this week.
>>
>> If you have the USB3 working in the kernel, can you point to a tree where I
>> can have a look at the drivers and dt-bindings ?
> Sure, you can see our downstream kernel code at my github, here is the link address: https://github.com/sherrysun1/linux-imx.git.
> And look forward to seeing your patches in uboot maillist.

It will take some times before I can post on the mailing list because I 
did the work on top TI's u-boot. But you can find the patches under 
https://github.com/jjhiblot/u-boot/tree/usb3_cleanup_v2. 
<https://github.com/jjhiblot/u-boot/tree/usb3_cleanup_v2>

The DTS bindings are the same as under Linux. The CDNS3 driver is a port 
of the iteration v11 of the linux driver that has just been merged in 
the linux usb tree 
(https://git.kernel.org/pub/scm/linux/kernel/git/balbi/usb.git/log/?h=next)

Care has been taken to keep the changes with linux minimal to ease the 
maintenance: the drivers are quite new and will probably evolve quite a 
bit in the next few months.

JJ

>
> Best regards
> Sherry sun
>
>> JJ
>>
>>> Best regards
>>> Sherry sun
>>>
>>>> Regards
>>>> Vignesh
>>>>
>>>>> Best regards
>>>>> Sherry sun
>>>>>
>>>>>> Regards
>>>>>> Vignesh
>>>>>>
>>>>>>> Best regards
>>>>>>> Sherry sun
>>>>>>>
>>>>>>>> JJ
>>>>>>>>
>>>>>>>>>> Then when binding the wrapper node, it will hard-coded the two
>>>>>>>> subnodes
>>>>>>>>>> to different driver(gadge/host driver) according to the dr_mode
>>>>>>>>>> property
>>>>>>>> in
>>>>>>>>>> nodes.
>>>>>>>>>>
>>>>>>>>> Do you think I understand it right?
>>>>>>>>> Best regards
>>>>>>>>> Sherry sun
>>>>>>>>>
>>>>>>>>>> Best regards
>>>>>>>>>> Sherry sun
>>>>>>>>>>
>>>>>>>>>>> JJ
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>>>>>>> +	{ }
>>>>>>>>>>>>>>>>> +};
>>>>>>>>>> _______________________________________________
>>>>>>>>>> U-Boot mailing list
>>>>>>>>>> U-Boot at lists.denx.de
>>>>>>>>>> https://l
>>>>>>>>>>
>> ists.d&data=02%7C01%7Csherry.sun%40nxp.com%7C7d1d76a7124f4c3f
>>>>>> e9
>> 9d08d72d3ddf82%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C63
>>>>>> 70276
>> 16080089878&sdata=70BPVQkomokcNpxsHRD3njfZQvuG51VSD1QKBjQ
>>>>>> o1kA%3
>>>>>>>>>> D&reserved=0
>>>>>>>>>> enx.de%2Flistinfo%2Fu-
>>>>>>>>>>
>> boot&data=02%7C01%7Csherry.sun%40nxp.com%7C35f1d34da1ea4b7
>> 670ba08d72b823e9a%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7
>> C637025710721487079&sdata=Nfk0qWtSViz60wJHAOr2m5tgIwTWjNwI
>>>>>>>>>> GrNOxDH6HC0%3D&reserved=0
>>>>>> --
>>>>>> Regards
>>>>>> Vignesh