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

[Marek Vasut <marex@denx.de>]

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@baylibre.com>
>>>>> Suggested-by: Roger Quadros <rogerq@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.