We have a situation where occasionally the USB glitches where the D- glitches low at or near an end of frame (EOF) or end of packet (EOP). We're using the TWL4030 with MUSB on an OMAP3 processor. We cannot tell where the glitch is originating. We're working on resolving this in both hardware and software, but I was hoping someone might have some insights on how to address it in software. We created a special test fixture to force the D- low for a moment during the EOP and EOF to attempt to compare the handling of other USB controllers and/or USB hubs. The reason I think it's unique to the MUSB controller or the TWL4030, because we cannot reproduce this issue using other USB controllers and/or other USB controllers handle the error condition. On an older, 3.0.x kernel, if we get a glitch on D-, the MUSB controller may become unresponsive to the point where a reboot becomes required. Testing this similar scenario with the 4.14-RC kernel, the MUSB controller drops the connection and re-enumerates almost immediately, which indicates to me that the error handling is getting better (or the glitching is reduced somehow). I have not seen a reboot be required. If I connect the same USB devices to a USB Hub and/or other USB controller and attempt to force this same condition with the test fixture, the high level USB code does not notice there is an error. There is no disconnect, no hanging, no loss of data. I am not a USB expert, but it seems like we might be able to handle the error in software and/or retry if necessary without dropping the connection. Might someone have any ideas or thoughts on how we might be able to tweak the software? thanks adam -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
