On Tue, Feb 27, 2018 at 7:47 AM, Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > On Tue, Feb 27, 2018 at 07:26:23AM -0500, Brent Sink wrote: >> Hi Greg, >> >> On Tue, Feb 27, 2018 at 4:16 AM, Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: >> > On Mon, Feb 26, 2018 at 10:05:35PM -0500, Brent Sink wrote: >> >> Hello, >> >> >> >> I'm trying to debug a problem I'm having with a usb-serial device >> >> (modem) when it's plugged into a USB port on a custom i.MX6 board. >> >> >> >> If I connect a USB to Serial converter (I'm using Prolific PL2303), >> >> and I short the RX and TX lines together so I read back what I write, >> >> I've noticed that I can send data correctly, but when I receive data >> >> it is missing the LSB. I've verified this by using a logic analyzer >> >> to make sure that when I type "A", the logic analyzer also reads "A". >> >> But when looking at the echo from minicom, it shows "@" instead. "B" >> >> = "B", "C" = "B", "D" = "D", "E" = "D", and so on. This same problem >> >> happens to the 3G and 4G modems, as they create ttyACMx ports and >> >> ModemManager is unable to talk to them because of this same issue. >> >> This happens on every board we had made, and I've tried using both >> >> Buildroot and Debian in case it was a rootfs issue... it's not. I >> >> also tried using a 3.14 kernel and 4.1.15 kernel - same problem exists >> >> in both versions. >> > >> > This sounds like you have a problem with your physical loopback device. >> > I suggest getting a different one and trying that out. >> > >> > good luck! >> > >> > greg k-h >> >> I'm not sure I understand what you mean by the physical loopback >> device? Do you mean the Prolific PL2303 device, or the modem, or >> something else? > > What ever you are using to "loop" the TX/RX lines together. Usually > this is a little "loopback" dongle that you plug into the device. Make > sure that is stable and works well. It seems that no matter what type > of device you plug yours into, it does not work, are you sure you have > all of the needed lines connected? I see. Yes, both a usb-serial adapter (using usb-serial driver), and modems (using cdc_acm driver) have the same problem. The usb-serial adapter is stable and works well - I've tested it with a RPi and it works just fine. Could something with the device tree influence these drivers? I added some printk lines to the cdc_acm.c driver to show what it is writing and what it is reading. As you can see towards the bottom of the dmesg below (at time 39.277549), I type an 'a', which it correctly recognizes as 0x61, but in the acm_process_read_urb and acm_read_bulk_callback methods it reads 0x60 instead. Also, I'm really confused that if I paste text into the terminal it makes it through ok. It's like if I fill the buffer quick enough, it works, but if I fill the buffer one character at a time it doesn't work. Not sure if that makes any sense...?? [ 3.755020] cdc_acm 1-1.1:1.0: interfaces are valid [ 3.845450] cdc_acm 1-1.1:1.0: ttyACM0: USB ACM device [ 3.846546] cdc_acm 1-1.1:1.0: acm_ctrl_msg - rq 0x20, val 0x0, len 0x7, result 7 [ 3.847188] cdc_acm 1-1.1:1.2: interfaces are valid [ 3.904252] cdc_acm 1-1.1:1.2: ttyACM1: USB ACM device [ 3.905153] cdc_acm 1-1.1:1.2: acm_ctrl_msg - rq 0x20, val 0x0, len 0x7, result 7 [ 3.918053] cdc_ether 1-1.1:1.8 usb0: register 'cdc_ether' at usb-ci_hdrc.1-1.1, CDC Ethernet Device, 6a:dc:65:00:ec:f6 [ 3.918189] usbcore: registered new interface driver cdc_ether [ 3.920624] cdc_acm 1-1.1:1.4: interfaces are valid [ 3.976558] cdc_acm 1-1.1:1.4: ttyACM2: USB ACM device [ 3.977600] cdc_acm 1-1.1:1.4: acm_ctrl_msg - rq 0x20, val 0x0, len 0x7, result 7 [ 3.978388] cdc_acm 1-1.1:1.6: interfaces are valid [ 4.058378] cdc_acm 1-1.1:1.6: ttyACM3: USB ACM device [ 4.062264] cdc_acm 1-1.1:1.6: acm_ctrl_msg - rq 0x20, val 0x0, len 0x7, result 7 [ 4.066925] cdc_acm 1-1.2:1.0: interfaces are valid [ 4.154076] cdc_acm 1-1.2:1.0: ttyACM4: USB ACM device [ 4.155176] cdc_acm 1-1.2:1.0: acm_ctrl_msg - rq 0x20, val 0x0, len 0x7, result 7 [ 4.155549] cdc_acm 1-1.2:1.2: interfaces are valid [ 4.189088] cdc_acm 1-1.2:1.2: ttyACM5: USB ACM device [ 4.191554] cdc_acm 1-1.2:1.2: acm_ctrl_msg - rq 0x20, val 0x0, len 0x7, result 7 [ 4.191882] cdc_acm 1-1.2:1.4: interfaces are valid [ 4.239954] cdc_acm 1-1.2:1.4: ttyACM6: USB ACM device [ 4.265495] cdc_acm 1-1.2:1.4: acm_ctrl_msg - rq 0x20, val 0x0, len 0x7, result 7 [ 4.265867] cdc_acm 1-1.2:1.6: interfaces are valid [ 4.299007] cdc_acm 1-1.2:1.6: ttyACM7: USB ACM device [ 4.301671] cdc_acm 1-1.2:1.6: acm_ctrl_msg - rq 0x20, val 0x0, len 0x7, result 7 [ 4.301990] cdc_acm 1-1.2:1.8: interfaces are valid [ 4.317575] cdc_acm 1-1.2:1.8: ttyACM8: USB ACM device [ 4.318397] cdc_acm 1-1.2:1.8: acm_ctrl_msg - rq 0x20, val 0x0, len 0x7, result 7 [ 4.318708] cdc_acm 1-1.2:1.10: interfaces are valid [ 4.345074] cdc_acm 1-1.2:1.10: ttyACM9: USB ACM device [ 4.346402] cdc_acm 1-1.2:1.10: acm_ctrl_msg - rq 0x20, val 0x0, len 0x7, result 7 [ 4.349568] usbcore: registered new interface driver cdc_acm [ 4.349576] cdc_acm: USB Abstract Control Model driver for USB modems and ISDN adapters [ 30.552284] tty ttyACM4: acm_tty_install [ 30.552331] tty ttyACM4: acm_tty_open [ 30.552342] cdc_acm 1-1.2:1.0: acm_port_activate [ 30.552458] cdc_acm 1-1.2:1.1: acm_submit_read_urb - urb 0 [ 30.552477] cdc_acm 1-1.2:1.1: acm_submit_read_urb - urb 1 [ 30.552490] cdc_acm 1-1.2:1.1: acm_submit_read_urb - urb 2 [ 30.552502] cdc_acm 1-1.2:1.1: acm_submit_read_urb - urb 3 [ 30.552514] cdc_acm 1-1.2:1.1: acm_submit_read_urb - urb 4 [ 30.552527] cdc_acm 1-1.2:1.1: acm_submit_read_urb - urb 5 [ 30.552539] cdc_acm 1-1.2:1.1: acm_submit_read_urb - urb 6 [ 30.552551] cdc_acm 1-1.2:1.1: acm_submit_read_urb - urb 7 [ 30.552563] cdc_acm 1-1.2:1.1: acm_submit_read_urb - urb 8 [ 30.552575] cdc_acm 1-1.2:1.1: acm_submit_read_urb - urb 9 [ 30.552587] cdc_acm 1-1.2:1.1: acm_submit_read_urb - urb 10 [ 30.552600] cdc_acm 1-1.2:1.1: acm_submit_read_urb - urb 11 [ 30.552612] cdc_acm 1-1.2:1.1: acm_submit_read_urb - urb 12 [ 30.552625] cdc_acm 1-1.2:1.1: acm_submit_read_urb - urb 13 [ 30.552636] cdc_acm 1-1.2:1.1: acm_submit_read_urb - urb 14 [ 30.552648] cdc_acm 1-1.2:1.1: acm_submit_read_urb - urb 15 [ 30.553660] cdc_acm 1-1.2:1.0: acm_ctrl_msg - rq 0x22, val 0x3, len 0x0, result 0 [ 30.553882] cdc_acm 1-1.2:1.0: acm_ctrl_irq - network connection: 1 [ 30.555880] cdc_acm 1-1.2:1.0: acm_ctrl_irq - network connection: 1 [ 39.277507] cdc_acm 1-1.2:1.1: acm_tty_write - count 1 [ 39.277532] cdc_acm 1-1.2:1.1: acm_tty_write - write 1 [ 39.277549] 61 a [ 39.277825] cdc_acm 1-1.2:1.1: acm_softint [ 39.289651] 60 ` [ 39.289674] cdc_acm 1-1.2:1.1: acm_read_bulk_callback - urb 0, len 1 [ 39.289687] 60 ` [ 39.289721] cdc_acm 1-1.2:1.1: acm_submit_read_urb - urb 0 > > thanks, > > greg k-h -- -brent -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
