Le Potato Invalid Argument

duskglow · May 12, 2022

Not sure if this is beginner or advanced, so I guess I'll start here.

I have a "le potato" I recently bought. Getting it working has been a nightmare, but I'm almost there. Right now my project is to get a 32x64 RGB matrix working using an adafruit hat. I got Armbian 22.02.1 Focal running on it, and I'm using the gpiod library.

I've had to write my own access library, but I've almost got it working, translating the pin labels ("7J1 Header Pin15") to the appropriate GPIO/offset values for use with gpiod. Except for exactly one. I try to use request_line on GPIO 22 (chip 0, offset 10) and it gives me an invalid argument.

Doesn't do this for any other GPIO and I'm at my wit's end. I see in the docs that this is a "TEST_N" pin with a double asterisk notation that it needs a recent kernel to set output, but mine is plenty recent enough. I've also verified triply that I'm trying to access gpiochip0, offset 10.

Some info that might be valuable.

Spoiler

Linux lepotato 5.10.102-meson64 #22.02.1 SMP PREEMPT Sun Feb 27 09:09:25 UTC 2022 aarch64 aarch64 aarch64 GNU/Linux

lepotato:~/rpi-rgb-led-matrix$ sudo gpioinfo
gpiochip0 - 11 lines:
        line   0:    "UART TX"       unused   input  active-high
        line   1:    "UART RX"       unused   input  active-high
        line   2:   "Blue LED" "librecomputer:blue" output active-high [used]
        line   3: "SDCard Voltage Switch" "VCC_CARD" output active-high [used]
        line   4: "7J1 Header Pin5" unused input active-high
        line   5: "7J1 Header Pin3" unused input active-high
        line   6: "7J1 Header Pin12" unused input active-high
        line   7:      "IR In"       unused   input  active-high
        line   8: "9J3 Switch HDMI CEC/7J1 Header " unused input active-high
        line   9: "7J1 Header Pin13" unused input active-high
        line  10: "7J1 Header Pin15" unused input active-high
gpiochip1 - 100 lines:
        line   0:      unnamed       unused   input  active-high
        line   1:      unnamed       unused   input  active-high
        line   2:      unnamed       unused   input  active-high
        line   3:      unnamed       unused   input  active-high
        line   4:      unnamed       unused   input  active-high
        line   5:      unnamed       unused   input  active-high
        line   6:      unnamed       unused   input  active-high
        line   7:      unnamed       unused   input  active-high
        line   8:      unnamed       unused   input  active-high
        line   9:      unnamed       unused   input  active-high
        line  10:      unnamed       unused   input  active-high
        line  11:      unnamed       unused   input  active-high
        line  12:      unnamed       unused   input  active-high
        line  13:      unnamed       unused   input  active-high
        line  14: "Eth Link LED" unused input active-high
        line  15: "Eth Activity LED" unused input active-high
        line  16:   "HDMI HPD"       unused   input  active-high
        line  17:   "HDMI SDA"       unused   input  active-high
        line  18:   "HDMI SCL"       unused   input  active-high
        line  19: "HDMI_5V_EN" "regulator-hdmi-5v" output active-high [used]
        line  20: "9J1 Header Pin2" unused input active-high
        line  21: "Analog Audio Mute" "enable" output active-high [used]
        line  22: "2J3 Header Pin6" unused input active-high
        line  23: "2J3 Header Pin5" unused input active-high
        line  24: "2J3 Header Pin4" unused input active-high
        line  25: "2J3 Header Pin3" unused input active-high
        line  26:    "eMMC D0"       unused   input  active-high
        line  27:    "eMMC D1"       unused   input  active-high
        line  28:    "eMMC D2"       unused   input  active-high
        line  29:    "eMMC D3"       unused   input  active-high
        line  30:    "eMMC D4"       unused   input  active-high
        line  31:    "eMMC D5"       unused   input  active-high
        line  32:    "eMMC D6"       unused   input  active-high
        line  33:    "eMMC D7"       unused   input  active-high
        line  34:   "eMMC Clk"       unused   input  active-high
        line  35: "eMMC Reset"      "reset"  output   active-low [used]
        line  36:   "eMMC CMD"       unused   input  active-high
        line  37: "ALT BOOT MODE" unused input active-high
        line  38:      unnamed       unused   input  active-high
        line  39:      unnamed       unused   input  active-high
        line  40:      unnamed       unused   input  active-high
        line  41: "eMMC Data Strobe" unused input active-high
        line  42:  "SDCard D1"       unused   input  active-high
        line  43:  "SDCard D0"       unused   input  active-high
        line  44: "SDCard CLK"       unused   input  active-high
        line  45: "SDCard CMD"       unused   input  active-high
        line  46:  "SDCard D3"       unused   input  active-high
        line  47:  "SDCard D2"       unused   input  active-high
        line  48: "SDCard Det"         "cd"   input   active-low [used]
        line  49:      unnamed       unused   input  active-high
        line  50:      unnamed       unused   input  active-high
        line  51:      unnamed       unused   input  active-high
        line  52:      unnamed       unused   input  active-high
        line  53:      unnamed       unused   input  active-high
        line  54:      unnamed       unused   input  active-high
        line  55:      unnamed       unused   input  active-high
        line  56:      unnamed       unused   input  active-high
        line  57:      unnamed       unused   input  active-high
        line  58:      unnamed       unused   input  active-high
        line  59:      unnamed       unused   input  active-high
        line  60:      unnamed       unused   input  active-high
        line  61:      unnamed       unused   input  active-high
        line  62:      unnamed       unused   input  active-high
        line  63:      unnamed       unused   input  active-high
        line  64:      unnamed       unused   input  active-high
        line  65:      unnamed       unused   input  active-high
        line  66:      unnamed       unused   input  active-high
        line  67:      unnamed       unused   input  active-high
        line  68:      unnamed       unused   input  active-high
        line  69:      unnamed       unused   input  active-high
        line  70:      unnamed       unused   input  active-high
        line  71:      unnamed       unused   input  active-high
        line  72:      unnamed       unused   input  active-high
        line  73:  "Green LED" "librecomputer:system-status" output active-high [used]
        line  74: "VCCK Enable" unused input active-high
        line  75: "7J1 Header Pin27" unused input active-high
        line  76: "7J1 Header Pin28" unused input active-high
        line  77: "VCCK Regulator" unused input active-high
        line  78: "VDDEE Regulator" unused input active-high
        line  79: "7J1 Header Pin22" unused input active-high
        line  80: "7J1 Header Pin26" unused input active-high
        line  81: "7J1 Header Pin36" unused input active-high
        line  82: "7J1 Header Pin38" unused input active-high
        line  83: "7J1 Header Pin40" unused input active-high
        line  84: "7J1 Header Pin37" unused input active-high
        line  85: "7J1 Header Pin33" unused input active-high
        line  86: "7J1 Header Pin35" unused input active-high
        line  87: "7J1 Header Pin19" unused input active-high
        line  88: "7J1 Header Pin21" unused input active-high
        line  89: "7J1 Header Pin24" unused input active-high
        line  90: "7J1 Header Pin23" unused input active-high
        line  91: "7J1 Header Pin8" unused input active-high
        line  92: "7J1 Header Pin10" unused input active-high
        line  93: "7J1 Header Pin16" unused input active-high
        line  94: "7J1 Header Pin18" unused input active-high
        line  95: "7J1 Header Pin32" unused input active-high
        line  96: "7J1 Header Pin29" unused input active-high
        line  97: "7J1 Header Pin31" unused input active-high
        line  98: "7J1 Header Pin7" unused input active-high
        line  99:      unnamed       unused   input  active-high

--- ADDING LINE ---
Adding pin 22: offset 10, label 7J1 Header Pin15
requesting...
terminate called after throwing an instance of 'std::system_error'
  what():  error requesting GPIO lines: Invalid argument
Aborted

Virtual cookies if you can help. Thanks.,

Edited May 16, 2022 by TRS-80
put long output inside spoiler

TonyMac32 · May 12, 2022

I have this hat and a couple potato's, if you can provide the scripts I could take a look. I am just getting my lab/office set back up, so it might take a bit longer to review than hoped for.

duskglow · May 13, 2022

Hi Tony, thanks. I can make a small program that will trigger this issue this weekend, I had to cannibalize the card for the rpi 3 because the project must go on, but new cards are arriving this weekend.

I will say that I discovered more, though. It's a gpxx potato, apparently there are a few different kinds. I also managed to track the fault across kernel boundaries and right into kernel space. The EINVAL is coming from the GPIO_V2_GET_LINE_IOCTL
ioctl, and while I don't understand exactly how it works, the problem *seems* to be that the GPIO22 (chip 0, offset 10, header pin 15) line is also the TEST_N line, and for some reason this line is in a different bank than the kernel pinctrl code is expecting.

I think this is true *only* for this particular line, and while it won't get in the way of most people, the adafruit hat uses this line, so it's kind of impossible to make that work properly at the moment (I actually made some really good progress at getting the rpi-rgb-led-matrix software to work using gpiod, but this is not surmountable at the present time.)

If this is not enough info, check back Sat. or Sun., I will post a small proof of concept program that will just exercise that line.

Thanks for getting back.