As reported by one of our users here: https://github.com/raspberrypi/linux/issues/3148 There is a bug when the dwc2 core receives USB data packets that are between 1 and 4 bytes in length - 4 bytes are always written to memory where the non-packet bytes are garbage. This is easily reproducible by - Plugging a UVC-compliant webcam into a Raspberry Pi gen 1, 2 or 3 product - Running "v4l2-ctl -d 0 --all" The camera's control ranges (brightness/contrast etc) are all queried by 1- or 2-byte control IN transfers. As 4 bytes get written to the URB's buffer, this results in the uvcvideo data struct containing the control information getting corrupted like so: contrast 0x00980901 (int) : min=0 max=64 step=1 default=57343 value=32 saturation 0x00980902 (int) : min=0 max=128 step=1 default=57343 value=105 hue 0x00980903 (int) : min=-40 max=40 step=1 default=-8193 value=0 white_balance_temperature_auto 0x0098090c (bool) : default=1 value=1 gamma 0x00980910 (int) : min=72 max=500 step=1 default=57343 value=100 [etc] We've implemented a downstream fix for dwc_otg[1] that just forces use of the dword alignment buffer mechanism (aka DMA bounce buffer), but dwc2 only uses a bounce buffer for split-IN transfers. I have two questions: 1) Does this bug occur on non-Pi hardware? 2) What's the easiest way to patch this for dwc2? [1] https://github.com/raspberrypi/linux/commit/c0e4ca17457d6669a263e86a88f0036875fc019e
