Add I2C device emulation support for ARM targets

[stephanosio]

Cherry-pick upstream patches to support I2C device emulation (e.g. LSM303DLHC magnetometer) for ARM targets

Zephyr SDK PR: zephyrproject-rtos/sdk-ng#449

[stephanosio]

@microbuilder

[microbuilder]

Thanks @stephanosio

For reference sake, this sensor can added to QEMU at startup via:

$ qemu-system-arm -M mps2-an521 -device loader,file=build/zephyr/zephyr.elf -serial stdio \
  -monitor tcp:localhost:4444,server,nowait \
  -device lsm303dlhc_mag,id=lsm303,address=0x1E

We can be automatically handles this in Zephyr with an addition like this to the project cmake file:

if(BOARD MATCHES "mps2_an521")
  list(APPEND QEMU_EXTRA_FLAGS -device lsm303dlhc_mag,id=lsm303,address=0x1E)
endif()

For the device tree (mps2_an521 or mps3_an547 assumed here):

&i2c_shield1 {
	lsm303dlhc-magn@1e {
		compatible = "st,lsm303dlhc-magn";
		reg = <0x1e>;
		label = "LSM303DLHC-MAGN";
	};
};

Config settings:

CONFIG_I2C=y
CONFIG_I2C_SHELL=y
CONFIG_LSM303DLHC_MAGN=y

[microbuilder]

To update values for the magn or temp sensor, you have a several options, but the easiest to quickly test is with the monitor interface (see -monitor in an earlier comment here), then:

$ nc localhost 4444
QEMU 6.0.93 monitor - type 'help' for more information
(qemu) qom-list /machine/peripheral/
(qemu) qom-set lsm303 mag-x 1000
(qemu) qom-set lsm303 temperature 23000

Note: For the magnetometer 1 = 0.001 uT, and for the temperature sensor 1 = 0.001 C

[MaureenHelm]

Cool! Looking forward to playing with this.

@yperess @erwango FYI

[yperess]

Thanks, very exciting

[microbuilder]

It's nice to have emulated devices that appear exactly the same as real HW on the I2C bus.

This should make testing specific edge cases with sensors much easier, although you'll need something to script the sensor data updates in parallel. Most languages have libraries to make communicting with QEMU possible, though, and it can be done in a bash script in a pinch.

I only emulate the magnetometer for now since it was a much simpler device than the accel (less than a dozen registers), but it's still useful as a proof of concept.

[erwango]

@avisconti FYI

[microbuilder]

This seems OK:

$ ./qemu-system-arm -device help | grep lsm
name "lsm303dlhc_mag", bus i2c-bus

$ ./qemu-system-arm -M mps2-an521 -S -monitor stdio \
  -device lsm303dlhc_mag,id=lsm303,address=0x1E

QEMU 6.2.0 monitor - type 'help' for more information
(qemu) VNC server running on ::1:5900
(qemu) qom-list /machine/peripheral
type (string)
lsm303 (child<lsm303dlhc_mag>)
(qemu) qom-get lsm303 temperature
0
(qemu) qom-set lsm303 temperature 23000
(qemu) qom-get lsm303 temperature
23000

After adding the DTS overlay and kconfig changes mentionned earlier in this PR, I built an image with:

$ west build -p -b mps2_an521 zephyr/samples/sensor/sensor_shell/

Then run it with:

$ ./qemu-system-arm -M mps2-an521 \
  -device loader,file=/home/ubuntu/zephyr/build/zephyr/zephyr.elf \
  -serial stdio   -monitor tcp:localhost:4444,server,nowait  \
   -device lsm303dlhc_mag,id=lsm303,address=0x1E
VNC server running on ::1:5900


uart:~$ i2c scan I2C_SHIELD1
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:             -- -- -- -- -- -- -- -- -- -- -- -- 
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- 1e -- 
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
70: -- -- -- -- -- -- -- --                         
1 devices found on I2C_SHIELD1

uart:~$ sensor get LSM303DLHC-MAGN magn_xyz
channel idx=11 magn_xyz x =   0.000000 y =   0.000000 z =   0.000000

Update the register values via QOM in the qemu terminal:

$ nc localhost 4444
(qemu) qom-list /machine/peripheral/lsm303
qom-list /machine/peripheral/lsm303
type (string)
parent_bus (link<bus>)
realized (bool)
hotplugged (bool)
hotpluggable (bool)
address (uint8)
mag-y (int)
temperature (int)
mag-z (int)
mag-x (int)
(qemu) qom-set lsm303 mag-x 1000
qom-set lsm303 mag-x 1000
(qemu) qom-set lsm303 mag-z 1500
qom-set lsm303 mag-z 1500

Then scan the device again in zephyr's shell:

uart:~$ sensor get LSM303DLHC-MAGN magn_xyz
channel idx=11 magn_xyz x =   0.010000 y =   0.000000 z =   0.014285

Note that the z value doesn't exactly match the expected 0.015 since it will scale inputs to the closest valid value based on the magnetometer gain, etc.