Re: USB init before using usb_serial_acm gadget?
Hi Sergey,
On Thu, 14 Apr 2022 at 20:31, Sergey Nazaryev sergey@coolautomation.com wrote:
Hi!
As I can see, recently [1] the implementation of USB ACM gadget has been merged into U-boot master. I tried to use it but the problem is that running `setenv stdout usbacm` on my board based on STM32MP157 leads to errors below:
STM32MP> setenv stdout usbacm couldn't find an available UDC g_dnl_register: failed!, error: -19 ## Error inserting "stdout" variable, errno=22
After some research I've found that USB OTG controller must be initialized somehow before we can actually start using any gadget. For instance, on my STM32MP board `dwc2_udc_otg_probe` should be called. My research shows that `usb_gadget_initalize` is responsible for it; so, for this reason, there are explicit calls of `usb_gadget_initialize` (e.g. usb_dnl_dfu [2], usb_dnl_sdp [3]) before actual usage of any gadget.
However, unlike all other gadgets, usb_serial_acm code and code that uses it don't call usb_gadget_initialize at all. Okay, I understand that usb_serial_acm shouldn't initialize USB controllers by itself, but it's still unclear who must be responsible for it.
So, my main question is: what's the best place for `usb_gadget_initialize` call? Should I put it to board-specific code (board/vendor/xxx.c) or maybe it's better to put `usb_gadget_initialize` into new `usb` subcommand (`usb otgstart` or something like that) and call it before `setenv stdout usbacm`?
Yes, you're right. I did not catch this problem because the iMX board/platform I've tested on automatically initializes the usb controller in the right role (peripheral) based on devicetree property... but it's specific to that host driver.
So I think the right place to call usb_gadget_initialize is probably before registering the acm gadget function into acm_stdio_start(). Can you try this? and submit a follow_up fix patch if working?
Regards, Loic
So I think the right place to call usb_gadget_initialize is probably before registering the acm gadget function into acm_stdio_start(). Can you try this? and submit a follow_up fix patch if working?
It's required for `usb_gadget_initialize` to provide a "USB controller index" as an argument. It's pretty obvious how to do it in "interactive world" (e.g. to ask user for this number via CLI, like it was in commands mentioned in my previous message) but in our case we need to provide this number in non-interactive manner.
There is not an elegant solution with hardcoding '0' as a controller index like it was done in `ether` gadget [1], but it seems that it was a temporary fix ("This is a preparatory work for DM support for UDC drivers") that occasionaly became a permament solution.
So, that's why I suggested to add a new subcommand to `usb` for OTG initialization: in my opinion, it's better to require an explicit call of something like `usb otgstart 0` than hardcoding a '0' into the code. One more option is to add a new environment variable to explictly specify a controller index, and read this variable from all places when it requires.
P.S. I already put `usb_gadget_intiialize(0)` to my board code, and ACM gadget started working; so the remaining problem is only to decide where is the best place for this call.
[1]: https://source.denx.de/u-boot/u-boot/-/blob/master/drivers/usb/gadget/ether....
On Sun, 17 Apr 2022 at 10:45, Sergey Nazaryev sergey@coolautomation.com wrote:
So I think the right place to call usb_gadget_initialize is probably before registering the acm gadget function into acm_stdio_start(). Can you try this? and submit a follow_up fix patch if working?
It's required for `usb_gadget_initialize` to provide a "USB controller index" as an argument. It's pretty obvious how to do it in "interactive world" (e.g. to ask user for this number via CLI, like it was in commands mentioned in my previous message) but in our case we need to provide this number in non-interactive manner.
There is not an elegant solution with hardcoding '0' as a controller index like it was done in `ether` gadget [1], but it seems that it was a temporary fix ("This is a preparatory work for DM support for UDC drivers") that occasionaly became a permament solution.
So, that's why I suggested to add a new subcommand to `usb` for OTG initialization: in my opinion, it's better to require an explicit call of something like `usb otgstart 0` than hardcoding a '0' into the code. One more option is to add a new environment variable to explictly specify a controller index, and read this variable from all places when it requires.
P.S. I already put `usb_gadget_intiialize(0)` to my board code, and ACM gadget started working; so the remaining problem is only to decide where is the best place for this call.
Yes, but whatever the solution, we also need to know the controller index from gadget driver, since we need it for usb_gadget_handle_interrupts(index). So an env or global variable would be at least a good start.
Regards, Loic
participants (2)
-
Loic Poulain -
Sergey Nazaryev