drivers: udc_dwc2: Initial Buffer DMA support

Implement absolute minimum necessary to get Buffer DMA working. Require
Data Cache to be disabled if DWC2 OTG has DMA enabled because the stack
does not currently guarantee cache line alignment for allocated buffers.

Set EPENA bit before disabling IN endpoints because it seems to be
necessary in Buffer DMA mode (without EPENA the wait for INEPNAKEFF does
time out). Setting EPENA should have no impact on Completer mode
operation (where EPENA is not necessary for INEPNAKEFF to trigger).

Programming Guide recommends programming SUPCnt to 3, but the only
advantage would be to be able to tell how many back-to-back SETUP packets
were received if there was no more than 3 back-to-back SETUPs. This
information doesn't seem to be useful. The disadvantage is that the
buffer needed for receiving SETUP packet must be able to hold SUPCnt
multiple of 8 bytes. Use SUPCnt 1 so the 8 bytes buffer is enough.

Make sure to clear StsPhseRcvd interrupt bit in Buffer DMA mode because
the DMA seems to prevent the SETUP Phase Done interrupt from triggering
if StsPhseRcvd is set. Clearing this bit doesn't seem to be necessary in
Completer mode. This bit is set on control transfers with data stage
from host to device.

Both Buffer DMA and Completer mode operation on nRF54H20DK was verified
using USB2CV Chapter 9 Tests and MSC Tests with Mass Storage sample.

Signed-off-by: Tomasz Moń <[email protected]>

Author: tmon-nordic

drivers/usb/udc/Kconfig.dwc2

@@ -10,6 +10,13 @@ config UDC_DWC2
 	help
 	  DWC2 USB device controller driver.
 
+config UDC_DWC2_DMA
+	bool "DWC2 USB DMA support"
+	default n
+	depends on UDC_DWC2
+	help
+	  Enable Buffer DMA if DWC2 USB controller supports Internal DMA.
+
 config UDC_DWC2_STACK_SIZE
 	int "UDC DWC2 driver internal thread stack size"
 	depends on UDC_DWC2