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

[Jean-Jacques Hiblot]

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@4104000 {
            compatible = "ti,j721e-usb";
            [....]
            usb0: usb@6010000 {         /* xhci reg address*/
                compatible = "cdns,usb3-1.0.1";
        dr_mode = "host";
        [....]
        }
            usb1: usb@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



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Regards
Vignesh
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