[PATCH] usb: dwc3: respect role-switch-default-mode

[Caleb Connolly]

Hi Marek,

On 24/06/2024 02:33, Marek Vasut wrote:
> On 6/21/24 4:11 AM, Caleb Connolly wrote:
>> * Factor out the common pattern of checking the dr_mode property on
>>    the usb node and it's parent
>> * Respect the usb-role-switch property, rather than requiring dr_mode be
>>    set
>> * Override OTG mode with the value in role-switch-default-mode
>>
>> The devicetree bindings don't dictate that dr_mode is a required
>> property, but the dwc3 driver would refuse to probe if it was unset
>> (this breaks the Qualcomm RB2 board which doesn't set it).
>>
>> Here, we update the driver to respect the other properties that can be
>> used to describe the controller, and more gracefully handle some of the
>> edge cases.
>>
>> Signed-off-by: Caleb Connolly <caleb.connolly at linaro.org>
>> ---
>> Cc: Ilias Apalodimas <ilias.apalodimas at linaro.org>
>> Cc: Neil Armstrong <neil.armstrong at linaro.org>
>> ---
>>   drivers/usb/dwc3/dwc3-generic.c | 56 +++++++++++++++++++++++++--------
>>   1 file changed, 43 insertions(+), 13 deletions(-)
>>
>> diff --git a/drivers/usb/dwc3/dwc3-generic.c 
>> b/drivers/usb/dwc3/dwc3-generic.c
>> index cbb5d61dfb0b..1cf8b90e8bbf 100644
>> --- a/drivers/usb/dwc3/dwc3-generic.c
>> +++ b/drivers/usb/dwc3/dwc3-generic.c
>> @@ -49,8 +49,46 @@ struct dwc3_generic_host_priv {
>>       struct dwc3_generic_priv gen_priv;
>>       struct udevice *vbus_supply;
>>   };
>> +/**
>> + * dwc3_get_preferred_dr_mode() - Get the preferred DR mode for the 
>> USB node
>> + *
>> + * Since we don't support dynamic role switching yet in dwc3, this is 
>> a slightly
>> + * opinionated wrapper around usb_get_dr_mode() which will respect the
>> + * role-switch-default-mode property if it is present and the dr_mode 
>> is OTG.
>> + *
>> + * @child: Node to get the DR mode for
>> + */
>> +static enum usb_dr_mode dwc3_get_preferred_dr_mode(ofnode node)
>> +{
>> +    enum usb_dr_mode mode;
>> +    bool is_role_switch = ofnode_has_property(node, "usb-role-switch");
> 
> The usb-role-switch DT property is not DWC3 specific, even in U-Boot it 
> is used by e.g. STM32MP15xx which is DWC2. This should be added to core 
> code.

I couldn't see an obvious way to add this desired behaviour without 
risking breaking some existing boards. Do you mean keep this as a new 
function but just move it to core code? Or update the existing 
get_dr_mode() function?
> 
> Also, it would be really good to sync the DWC3 driver with more up to 
> date Linux state, but that's out of the scope of this patch obviously.

Yes, I'm definitely feeling this. Last time I tried updating dwc3 as you 
suggested (reverting all patches since the Linux import, updating, 
re-applying)... But there have just been too many changes on the Linux 
side for this to work anymore, and too many arch specific dwc3 glue 
drivers which call into the core that might break.

I would love it if we could figure out some path forward here, even if 
that's just someone spending more than half a day on the porting effort :D

-- 
// Caleb (they/them)