Finding power switch GPIO/ testing all possible GPIO

pparent76 · July 9, 2018, 9:44am

Hi,

I'm trying to port Openwrt to this device:

The issue is that they have a GPIO that controls the 3G card power supply. But I can't find which one and how to access it.

1°) Is there a way to know which gpio it is from the factory firmware? It is mounted to /sys/class/gpio/3g_power/ , but I do not have sources.
2°) Is there a way to modify dts so that all pins are availliable as GPIO, and so that I can manually test them one by one, to see if they trigger power supply for 3g?

Thank's a lot in adavance.
Pierre.

robimarko · July 9, 2018, 10:13am

Do you have a firmware upgrade image maybe?
If its using DTS you could extract DTB fromt the uImage and convert it back to DTS with DTC

pparent76 · July 9, 2018, 10:15am

Ok thank's I will try to see if I can get a firmware image from the manufacturer.

pparent76 · July 9, 2018, 10:44am

Also is there maybe a way to dump uimage from the device itself running their firmware?

(It is based on openwrt 14.04 so it is most probably using dts)

robimarko · July 9, 2018, 10:55am

You can try dumping the firmware partition and then use binwalk to inspect it and extract the dtb

juppin · July 9, 2018, 11:05am

If you have a dts based device, then you will have /sys/firmware/devicetree/base/ with all nodes and properties of your used device tree populated...

Here you can read also something like the gpio number... Your gpio should be under gpio-export as in my example.

Example for WDR3600 (ath79):

hexdump /sys/firmware/devicetree/base/gpio-export/gpio_usb2_power/gpios 
0000000 0000 000f 0000 0015 0000 0000

0000 000f = phandle to gpio-controller node
0000 0015 = gpio number in hex (here gpio 21 on gpio controller with phandle 0000 000f)
0000 0000 = active high (0000 0001 = active low)

Output of phandle from gpio controller:

hexdump /sys/firmware/devicetree/base/ahb/apb/gpio@18040000/phandle 
0000000 0000 000f

You can search for all available gpio-controllers with
find /sys/firmware/devicetree/base -name gpio-controller

Example for WDR3600 (ATH79):

find /sys/firmware/devicetree/base -name gpio-controller
/sys/firmware/devicetree/base/ahb/apb/gpio@18040000/gpio-controller
/sys/firmware/devicetree/base/ahb/apb/pcie-controller@180c0000/wifi@168c,0033/gpio-controller

This device does have two gpio controllers.

pparent76 · July 9, 2018, 11:43am

@robimarko

Ok I could extract it with

dd if=/dev/mtdblock3 of=/tmp/test3.dump

Then

binwalk -e test3.dump

I get

DECIMAL       HEXADECIMAL     DESCRIPTION
--------------------------------------------------------------------------------
0             0x0             uImage header, header size: 64 bytes, header CRC: 0x3A30D79, created: Thu Jan 18 00:16:36 2018, image size: 1076996 bytes, Data Address: 0x80000000, Entry Point: 0x80000000, data CRC: 0x6C2D491D, OS: Linux, CPU: MIPS, image type: OS Kernel Image, compression type: lzma, image name: "MIPS OpenWrt Linux-3.10.49"
64            0x40            LZMA compressed data, properties: 0x6D, dictionary size: 8388608 bytes, uncompressed size: 3213996 bytes
1077060       0x106F44        Squashfs filesystem, little endian, version 4.0, compression:lzma (non-standard type definition), size: 7511348 bytes,  2031 inodes, blocksize: 262144 bytes, created: Thu Jan 18 00:16:31 2018
8650752       0x840000        JFFS2 filesystem, little endian

And I have a file 40.7z which obviously is the uImage. Now i need to find how to extract dts from it.

robimarko · July 9, 2018, 11:44am

You should also have file 40
Simply use device tree compiler.
It has really good --help page that is pretty self explanatory

pparent76 · July 9, 2018, 11:45am

@juppin

There is no such folder. Their firmware is based on 14.04 , should there be /sys/firmware/devicetree/base/ on 14.04?

juppin · July 9, 2018, 11:46am

Binwalk didn´t find a dtb...
This is no dts based kernel!

Only the rootfs is based on openwrt i think... Kernel is from vendor!

pparent76 · July 9, 2018, 11:47am

Indeed

uname -a
Linux G3 3.10.49 #217 Thu Jan 18 07:16:22 CST 2018 mips GNU/Linux

So is there a way to test all processor pins one by one, to see which one is enabling power for 3g?

juppin · July 9, 2018, 11:49am

https://openwrt.org/docs/guide-developer/add.new.device

pparent76 · July 9, 2018, 11:54am

@juppin

If you're suggesting this method:

cd /sys/class/gpio
GPIO=3
echo $GPIO > export
echo "out" > gpio$GPIO/direction
echo 0 > gpio$GPIO/value
sleep 1s
echo 1 > gpio$GPIO/value
sleep 1s
echo $GPIO > unexport

I've already tested, but by default only very few pins are available as gpio (6 I believe). And none of them triggers 3g power. I guess some configuration needs to be put in dts so that processors pin are muxed as gpio?

juppin · July 9, 2018, 12:07pm

Seems you could not export a gpio that is already exported with gpio-export.

pparent76 · July 9, 2018, 12:10pm

On MY firmware based on 15.05, I can export:

gpio1 gpio2 gpio37 gpio38 gpio39 gpio72

All other refuse to export with my current dts ( ZBT-WA05.dts ), none of theses is the one I'm looking for.

pparent76 · July 9, 2018, 1:34pm

Ok so I got the info form the manufacturer the pin that controls the power supply is H2 (i.e EPHY _LED2 _N _JTMS )

Any idea how to get it available as a GPIO?

robimarko · July 9, 2018, 1:39pm

It should be GPIO 42
Check page 22 of the datasheet.
But I think you gotta disable JTAG and Switch LED modes so its exposed as GPIO.

Check out page 37 of Programming guide.
http://download.villagetelco.org/hardware/MT7620/MT7620_ProgrammingGuide.pdf

EPHY_LED_GPIO _MODE

pparent76 · July 9, 2018, 1:47pm

Yes the pin multiplexing is not correctly done.

I will try to see if I can do something with that:

http://wiki.wrtnode.com/index.php?title=Released_multiused_GPIO_and_register_gpio-leds

I will need a bit of time, I keep you updated.

robimarko · July 9, 2018, 1:47pm

You can do something like this:

Just the mode needs to be changed

mkresin · July 9, 2018, 1:56pm

The following might be helpful: