Making calls work on PinePhone
------------------------------

Modem needs to be setup with:

  AT+QDAI=1,0,0,1,0,1,1,1
  AT+QDAI?

and restarted.
  
This sets modem to:

  1 - Digital PCM
  0 - I2S master
  0 - Primary mode (short sync)
  1 - 256kHz clock (256kHz / 16bit = 16k samples/s)
  0 - 16bit linear format
  1 - 16kHz sample
  1 - 1 slot
  1 - map to first slot (the only slot)

The SoC I2S0 interface needs to be configured to match this. To try various
configurations in real-time we can run pulseaudio and set it up so that:

1) alsamixer

  - set "Line Out Source" to "Mono Differential"
  - Unmute "AIF1 Slot 0 Digital DAC"
  - (optional) unmute the microphone / mute loudpeaker

2) pulseaudio

  # Outbound - connect audio from aif1 to i2s0
  pactl load-module module-loopback \
  	source=alsa_input.platform-sound.stereo-fallback \
  	sink=alsa_output.platform-sound-modem.mono-fallback

  # Inbound - connect audio from i2s0 to aif1
  pactl load-module module-loopback \
  	source=alsa_input.platform-sound-modem.mono-fallback \
  	sink=alsa_output.platform-sound.stereo-fallback

To test inbound audio, we can play audio using modem's TTS (text to speech
functionality):

  AT+QTTS=2,"Welcome to use the module of QUECTEL"

To test outbound, we can make a call. I call the pinephone from a dumbphone
and answer the call with:

  ATA

I2S interface module has quite a lot of toggles/bits that can be configured,
and the right configuration was found to be:

I2S0: (initial)
0x01c22000 : 00000107
0x01c22004 : 00000f33
0x01c22008 : 00000030
0x01c2200c : 00000000
0x01c22010 : 00000000
0x01c22014 : 000400f5
0x01c22018 : 00390000
0x01c2201c : 00000088
0x01c22020 : 00000000
0x01c22024 : 000001c4
0x01c22028 : 00000000
0x01c2202c : 00000000
0x01c22030 : 00000000
0x01c22034 : 00001010
0x01c22038 : 00000000
0x01c2203c : 00000000
0x01c22040 : 00000000
0x01c22044 : 76543210
0x01c22048 : 00000000
0x01c2204c : 00000000
0x01c22050 : 00000000
0x01c22054 : 00001000
0x01c22058 : 76543210
0x01c2205c : 00000050

I2S0: (working)
0x01c22000 : 00000107
0x01c22004 : 00080f33
0x01c22008 : 00000030
0x01c2200c : 00000004
0x01c22010 : 00000006
0x01c22014 : 000400f5
0x01c22018 : 003e010e
0x01c2201c : 00000088
0x01c22020 : 00000000
0x01c22024 : 000001c4
0x01c22028 : 00316016
0x01c2202c : 00314b88
0x01c22030 : 00000000
0x01c22034 : 00000010
0x01c22038 : 00000000
0x01c2203c : 00000000
0x01c22040 : 00000000
0x01c22044 : 76543210
0x01c22048 : 00000000
0x01c2204c : 00000000
0x01c22050 : 00000000
0x01c22054 : 00001000
0x01c22058 : 76543210
0x01c2205c : 00000050

The only difference comapred to what kernels configures is that TX offset should be
set to 0. and RX offset to 1 (already is).

Linux kernel with necessary patches and DTS changes integrated is available at:

  https://megous.com/git/linux/log/?h=pp-5.5
  
If you want to build my kernel, use this branch, because pp-5.5 branch is not
standalone and depends on ths-5.5 branch. orange-pi-5.5 is integration
branch for all my kernel work:
  
  https://megous.com/git/linux/log/?h=orange-pi-5.5


To enable the modem in my kernel you need to run this script (only on DEV
phone version 1.0!!):

-------------------------------------------
#!/bin/sh

GPIO=/sys/class/gpio
PIN=/sys/class/gpio/gpio
PB3_PWRKEY=35
PL7_PWR=359
PC4_RESET=68
PH8_DISABLE=232
PH7_WAKEUP=231

echo $PL7_PWR > $GPIO/export
echo $PC4_RESET > $GPIO/export
echo $PH7_WAKEUP > $GPIO/export
echo $PH8_DISABLE > $GPIO/export
echo $PB3_PWRKEY > $GPIO/export

echo out > $PIN$PH8_DISABLE/direction
echo out > $PIN$PH7_WAKEUP/direction
echo out > $PIN$PC4_RESET/direction
echo out > $PIN$PL7_PWR/direction
echo out > $PIN$PB3_PWRKEY/direction

echo 0 > $PIN$PH8_DISABLE/value
echo 0 > $PIN$PH7_WAKEUP/value
echo 0 > $PIN$PC4_RESET/value

echo 1 > $PIN$PL7_PWR/value
sleep 0.1
echo 1 > $PIN$PB3_PWRKEY/value
sleep 0.2
echo 0 > $PIN$PB3_PWRKEY/value
-------------------------------------------

To disable the modem before poweroff/reboot:

-------------------------------------------
#!/bin/sh

GPIO=/sys/class/gpio
PIN=/sys/class/gpio/gpio
PB3_PWRKEY=35
PL7_PWR=359
PC4_RESET=68
PH8_DISABLE=232
PH7_WAKEUP=231

echo 1 > $PIN$PB3_PWRKEY/value
sleep 0.8
echo 0 > $PIN$PB3_PWRKEY/value

echo waiting for shutdown
sleep 30

echo 0 > $PIN$PL7_PWR/value
-------------------------------------------


Enjoy!

   ~megi