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.
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