[PATCH 0/2] AM62A DWC3: Add support for USB DFU boot in OTG mode

[Siddharth Vadapalli]

Hello Roger,

On 28-11-2024 18:15, Roger Quadros wrote:
> 
> 
> On 26/11/2024 14:03, Siddharth Vadapalli wrote:
>> Hello,
>>
>> This series adds support for USB DFU boot on TI's AM62A SoC which has
>> two instances of DWC3 USB Controllers namely USB0 and USB1. The USB0
>> instance of the USB Controller supports USB DFU boot:
>> ROM => tiboot3.bin => tispl.bin => u-boot.img
>>
>> USB DFU Boot requires the USB Controller to be configured for Gadget
>> mode of operation. Since the USB0 instance of the DWC3 USB Controller
>> supports both Host and Gadget modes of operation via the Type-C interface
>> on the AM62A7-SK board, the device-tree specifies the "dr_mode" as "OTG".
>> However, there is currently no support for dynamically switching the "mode"
>> from Host to Gadget and vice-versa with the help of a state-machine.
>> The OTG mode is treated as a separate mode in itself rather than being
>> treated as an intermediate stage before assuming the Host/Gadget mode.
>> Due to this, USB DFU boot via the Type-C interface doesn't work as the
>> USB Controller hasn't been appropriately configured for Device/Gadget
>> mode of operation. One option is to change the device-tree to specify
>> "dr_mode" as "peripheral" and force the controller to assume the Device
>> role. This will imply that the U-Boot device-tree for AM62A diverges
>> from its Linux counterpart. Therefore, with the intent of keeping the
>> device-tree uniform across Linux and U-Boot, and at the same time, in
>> order to enable USB DFU boot in "OTG" mode with the DWC3 Controller,
>> the first patch in this series sets the "mode" on the basis of the
>> caller function, rather than using the "dr_mode" property in the
>> device-tree. There are only two callers of "dwc3_generic_probe()",
>> each of which clearly specify the expected mode of configuration.
>> This will enable both Host and Device mode of operation based on the
>> command executed by the user, thereby truly supporting "OTG"
>> functionality when the USB Controller supports it.
> 
> We don't really support OTG state machine. All you are supporting is
> user initiated role change.

I should have probably used the term "Dual Role" instead of "OTG". I
meant to say that the controller can be used both as Host and Device
based on the command executed by the user, if the controller's dr_mode
is "otg". I am aware that we don't support the OTG state machine in
U-Boot unlike Linux, which is why I have posted this series as a
workaround to utilize both Host and Device modes in the interim.

[...]

-- 
Regards,
Siddharth.