[PATCH] usb: gadget: dwc2_udc_otg: implement pullup()

[Mattijs Korpershoek]

On Tue, Jan 10, 2023 at 14:45, Marek Vasut <marex at denx.de> wrote:

> On 1/10/23 14:39, Mattijs Korpershoek wrote:
>> Hi Harald,
>> 
>> Thank you for your review.
>> 
>> On Tue, Jan 10, 2023 at 14:30, Harald Seiler <hws at denx.de> wrote:
>> 
>>> Hi,
>>>
>>> On Tue, 2023-01-10 at 10:11 +0100, Mattijs Korpershoek wrote:
>>>> Pullup is used by the usb framework in order to do software-controlled
>>>> usb_gadget_connect() and usb_gadget_disconnect().
>>>>
>>>> Implement pullup() for dwc2 using the SOFT_DISCONNECT bit in the dctl
>>>> register.
>>>>
>>>> This is especially useful when a gadget disconnection is initiated but
>>>> no board_usb_cleanup() is called.
>>>>
>>>> Signed-off-by: Mattijs Korpershoek <mkorpershoek at baylibre.com>
>>>> ---
>>>> On some boards using the dwc2 controller, like the Khadas VIM3L, whenever
>>>> usb_gadget_release() is called, the D+ and D- lines are in an unknown state.
>>>>
>>>> Because of that, the host can't detect usb disconnection.
>>>>
>>>> It was attempted to be be fixed with [1] but ended up doing the gadget disconnection
>>>> too early, creating issues on NXP-based boards which use uuu [2].
>>>>
>>>> By implementing pullup() in the controller driver, we ensure that the disconnection will
>>>> only be done when the framework calls usb_gadget_disconnect().
>>>>
>>>> [1] https://lore.kernel.org/all/20220728-reset-usb-controller-v2-1-ef7657ce78b1@baylibre.com/
>>>> [2] https://lore.kernel.org/all/20230107164807.3597020-1-dario.binacchi@amarulasolutions.com/
>>>> ---
>>>>   drivers/usb/gadget/dwc2_udc_otg.c | 16 ++++++++++++++++
>>>>   1 file changed, 16 insertions(+)
>>>>
>>>> diff --git a/drivers/usb/gadget/dwc2_udc_otg.c b/drivers/usb/gadget/dwc2_udc_otg.c
>>>> index 77988f78ab30..93ed9712d18a 100644
>>>> --- a/drivers/usb/gadget/dwc2_udc_otg.c
>>>> +++ b/drivers/usb/gadget/dwc2_udc_otg.c
>>>> @@ -236,6 +236,21 @@ static int udc_enable(struct dwc2_udc *dev)
>>>>   	return 0;
>>>>   }
>>>>   
>>>> +static int dwc2_gadget_pullup(struct usb_gadget *g, int is_on)
>>>> +{
>>>> +	unsigned int uTemp;
>>>
>>> Just some minor points about style...
>>>
>>> I think the `u32` type should be used for 32-bit registers instead.
>>> More explicit and no room for accidentally choosing the wrong size.
>>>
>>> Also, U-Boot and Linux don't use hungarian notation for variable names,
>>> just call it `tmp` or even better `dctl` to be explicit.
>> 
>> I agree with this. I actually picked up some of the code from
>> reconfig_usbd() where hungarian nototation is used. That's also where
>> the unsigned int comes from.
>> 
>> Sorry I did not convert it to some more Linux/U-Boot oriented style
>> before submitting.
>> 
>>>
>>>> +
>>>> +	is_on = !!is_on;
>>>
>>> This is superfluous, the if condition works either way.
>> 
>> Ack.
>> 
>> The maintainer (Marek) already picked this up in his usb tree:
>> https://lore.kernel.org/all/1f2c5d74-faae-42f8-5d4d-dfc08cb093aa@denx.de/
>> 
>> Should I send a clean-up/follow-up patch for this?
>
> The maintainer already dropped it and waits for V2 :)

Thank you, will send a V2 shortly.