[PATCH v3 09/12] usb: cdns3: Handle otg mode as peripheral

[Marek Vasut]

On 8/19/23 09:00, Roger Quadros wrote:
> +Peter & Pawel.
> 
> On 19/08/2023 02:47, Marek Vasut wrote:
>> On 8/18/23 21:26, Roger Quadros wrote:
>>>
>>>
>>> On 18/08/2023 21:48, Tom Rini wrote:
>>>> On Thu, Aug 17, 2023 at 11:15:17AM +0300, Roger Quadros wrote:
>>>>> Hi Tom,
>>>>>
>>>>> On 14/08/2023 20:17, Tom Rini wrote:
>>>>>> On Thu, Jul 13, 2023 at 03:45:42PM +0200, Julien Panis wrote:
>>>>>>
>>>>>>> Override 'otg' to 'peripheral' mode, since 'otg' mode
>>>>>>> is not yet supported by u-boot.
>>>>>>>
>>>>>>> Signed-off-by: Julien Panis <jpanis at baylibre.com>
>>>>>>> Suggested-by: Roger Quadros <rogerq at kernel.org>
>>>>>>> ---
>>>>>>>    drivers/usb/cdns3/core.c | 4 ++++
>>>>>>>    1 file changed, 4 insertions(+)
>>>>>>>
>>>>>>> diff --git a/drivers/usb/cdns3/core.c b/drivers/usb/cdns3/core.c
>>>>>>> index 644a9791b9c9..bd763fc593e1 100644
>>>>>>> --- a/drivers/usb/cdns3/core.c
>>>>>>> +++ b/drivers/usb/cdns3/core.c
>>>>>>> @@ -149,6 +149,10 @@ static int cdns3_core_init_role(struct cdns3 *cdns)
>>>>>>>          dr_mode = best_dr_mode;
>>>>>>>    +    /* u-boot doesn't yet support OTG so limit to PERIPHERAL */
>>>>>>> +    if (dr_mode == USB_DR_MODE_OTG)
>>>>>>> +        dr_mode = USB_DR_MODE_PERIPHERAL;
>>>>>>> +
>>>>>>>    #if defined(CONFIG_SPL_USB_HOST) || !defined(CONFIG_SPL_BUILD)
>>>>>>>        if (dr_mode == USB_DR_MODE_OTG || dr_mode == USB_DR_MODE_HOST) {
>>>>>>>            ret = cdns3_host_init(cdns);
>>>>>>
>>>>>> Julien, why don't we support otg mode here?
>>>>>>
>>>>>
>>>>> dr_mode will never be OTG at this point as the previous if condition
>>>>> would have forced it to PERIPHERAL.
>>>>>
>>>>> My understanding was that u-boot USB framework doesn't support OTG mode
>>>>> so we force it to PERIPHERAL.
>>>>
>>>> Well, the first part of this series is "make unknown state be OTG" for
>>>> DWC3, so we do in general (and Marek told me off-list he's used it on
>>>> DWC2 as well), so it sounds like these (CDNS3, MUSB) drivers need fixing
>>>> / updating.
>>>>
>>>
>>> CDNS3 does not have an internal OTG state machine. We mostly really care
>>> about role switching and not the full OTG stack. There needs to be
>>> some kind of SW framework to do that in u-boot.
>>>
>>> Marek could you please advise what can be done here?
>>
>> As far as I can tell, MX8MM (CI HDRC), STM32MP1 (DWC2) all can do the host/peripheral switching. Why is that a problem with CDNS3 ? I am not familiar with this controller btw.
> 
> So for MX8MM and STM32MP1, do  we support on the fly host/peripheral switching based on USB plug type?
> As we don't have interrupts, do you keep polling for ID status change?

Nope, you just plug in one cable or the other and run the matching 
command -- either 'usb reset' for Host or 'ums/dfu/...' for Peripheral .

> CDNS3 does support host/peripheral switching. i.e. cdsn3_hw_role_state_machine() and drd.c.
> What we are missing is the interrupt logic to map ID pin status change to role change.

I don't think you need any interrupt logic for this to work ?