Hello!
I'm trying to add I2C devices to I2C/SMBus buses via the ACPI SSDT
overlay method. I've managed to do it for the I2C buses, but can't get
it working for the SMBus (PIIX4).
Now the long description of what I've tried and learned.
I've successfully managed to add my I2C devices to the I2C buses. In
this case I2C buses are described in the ACPI code of my system like
this:
```
Device (I2CF)
{
Name (_HID, "AMDI0010")
Name (_UID, 0x05)
Method (_CRS, 0, Serialized) {...}
Method (_STA, 0, NotSerialized) {...}
}
```
These buses are present in the system as:
```
$ i2cdetect -l
i2c-0 unknown Synopsys DesignWare I2C adapter N/A
...
```
For my custom device (at24 EEPROM) I've created SSDT table:
```
DefinitionBlock ("at24.aml", "SSDT", 5, "", "AT24", 1)
{
External (_SB_.I2CF, DeviceObj)
Scope (\_SB.I2CF)
{
Device (EEP0) {
Name (_HID, "PRP0001")
Name (_DDN, "Atmel AT24 compatible EEPROM")
Name (_CRS, ResourceTemplate () {
I2cSerialBusV2 (
0x0050, // I2C Slave Address
ControllerInitiated,
400000, // Bus speed
AddressingMode7Bit,
"\\_SB.I2CF", // Link to ACPI I2C host controller
0
)
})
Name (_DSD, Package () {
ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
Package () {
Package () { "compatible", Package() { "atmel,24c128" } },
}
})
}
}
}
```
And after I've loaded it via 'acpi_configfs' I can successfully see
EEPROM in the system:
```
root@ubuntu-SP3:/home/ubuntu/acpi/custom# hexdump -C
/sys/bus/i2c/devices/i2c-PRP0001\:00/eeprom
00000000 63 6a a9 05 00 65 14 35 9f 81 a7 60 aa c2 18 d2 |cj...e.5...`....|
00000010 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff |................|
*
00004000
```
Now I'm trying to add devices to the SMBus bus. Which in my case is
produced from the i2c_piix4 PCI device:
```
$ lspci -s 00:14.0 -vvvxxx
00:14.0 SMBus: Advanced Micro Devices, Inc. [AMD] FCH SMBus Controller (rev 61)
Subsystem: Advanced Micro Devices, Inc. [AMD] FCH SMBus Controller
Control: I/O+ Mem+ BusMaster- SpecCycle- MemWINV- VGASnoop-
ParErr- Stepping- SERR- FastB2B- DisINTx+
Status: Cap- 66MHz+ UDF- FastB2B- ParErr- DEVSEL=medium
>TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
NUMA node: 0
IOMMU group: 58
Kernel driver in use: piix4_smbus
Kernel modules: i2c_piix4, sp5100_tco
00: 22 10 0b 79 03 04 20 02 61 00 05 0c 00 00 80 00
10: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
20: 00 00 00 00 00 00 00 00 00 00 00 00 22 10 0b 79
30: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
```
It is described as simple as this in the system ACPI code:
```
Device (SMBS) // \_SB_.PCI0.SMBS
{
Name (_ADR, 0x00140000) // _ADR: Address
}
```
And produces several I2C busses to the system:
```
i2c-7 unknown SMBus PIIX4 adapter port 0 at 0b00 N/A
i2c-8 unknown SMBus PIIX4 adapter port 2 at 0b00 N/A
i2c-9 unknown SMBus PIIX4 adapter port 1 at 0b20 N/A
```
No matter how I've tried, I can't get to add my custom devices to
these SMBus buses.
Apparently just using "\\_SB.PCI0.SMBS" is not enough for this case.
Maybe I need to somehow create port nodes for this Device? Or maybe it
is not possible at all with the current piix driver?
Anyway I've started digging and I've noticed that for the I2C device
there are two physical_nodes in the sysfs. Where the 'physical_node'
is a standard folder and 'physical_node1' is a direct link to the
proper i2c bus:
```
$ ls -la /sys/bus/acpi/devices/AMDI0010\:03/
total 0
drwxr-xr-x 4 root root 0 Nov 7 18:07 .
drwxr-xr-x 294 root root 0 Nov 7 18:05 ..
-r--r--r-- 1 root root 4096 Nov 7 18:06 hid
-r--r--r-- 1 root root 4096 Nov 7 18:06 modalias
-r--r--r-- 1 root root 4096 Nov 7 18:06 path
lrwxrwxrwx 1 root root 0 Nov 7 18:06 physical_node ->
../../../platform/AMDI0010:03
lrwxrwxrwx 1 root root 0 Nov 7 18:06 physical_node1 ->
../../../platform/AMDI0010:03/i2c-1
drwxr-xr-x 2 root root 0 Nov 7 18:06 power
-r--r--r-- 1 root root 4096 Nov 7 18:06 status
lrwxrwxrwx 1 root root 0 Nov 7 18:05 subsystem -> ../../../../bus/acpi
-rw-r--r-- 1 root root 4096 Nov 7 18:05 uevent
-r--r--r-- 1 root root 4096 Nov 7 18:06 uid
drwxr-xr-x 3 root root 0 Nov 7 18:05 wakeup
$ ls -la /sys/bus/acpi/devices/AMDI0010\:03/physical_node/
total 0
drwxr-xr-x 4 root root 0 Nov 7 18:08 .
drwxr-xr-x 7335 root root 0 Nov 7 18:05 ..
lrwxrwxrwx 1 root root 0 Nov 7 18:05 driver ->
../../../bus/platform/drivers/i2c_designware
-rw-r--r-- 1 root root 4096 Nov 7 18:08 driver_override
lrwxrwxrwx 1 root root 0 Nov 7 18:08 firmware_node ->
../../LNXSYSTM:00/LNXSYBUS:00/AMDI0010:03
drwxr-xr-x 4 root root 0 Nov 7 18:05 i2c-1
-r--r--r-- 1 root root 4096 Nov 7 18:08 modalias
drwxr-xr-x 2 root root 0 Nov 7 18:08 power
lrwxrwxrwx 1 root root 0 Nov 7 18:05 subsystem -> ../../../bus/platform
-rw-r--r-- 1 root root 4096 Nov 7 18:05 uevent
$ ls -la /sys/bus/acpi/devices/AMDI0010\:03/physical_node1/
total 0
drwxr-xr-x 4 root root 0 Nov 7 18:08 .
drwxr-xr-x 4 root root 0 Nov 7 18:08 ..
--w------- 1 root root 4096 Nov 7 18:08 delete_device
lrwxrwxrwx 1 root root 0 Nov 7 18:08 device -> ../../AMDI0010:03
lrwxrwxrwx 1 root root 0 Nov 7 18:08 firmware_node ->
../../../LNXSYSTM:00/LNXSYBUS:00/AMDI0010:03
drwxr-xr-x 3 root root 0 Nov 7 18:05 i2c-dev
-r--r--r-- 1 root root 4096 Nov 7 18:05 name
--w------- 1 root root 4096 Nov 7 18:08 new_device
drwxr-xr-x 2 root root 0 Nov 7 18:08 power
lrwxrwxrwx 1 root root 0 Nov 7 18:05 subsystem -> ../../../../bus/i2c
-rw-r--r-- 1 root root 4096 Nov 7 18:05 uevent
-r--r--r-- 1 root root 4096 Nov 7 18:08 waiting_for_supplier
```
But in the case of SMBus there is only one 'physical_node' folder (but
3 i2c buses) :
```
$ ls -l /sys/bus/acpi/devices/device\:25/
total 0
-r--r--r-- 1 root root 4096 Nov 7 18:07 adr
-r--r--r-- 1 root root 4096 Nov 7 18:07 path
lrwxrwxrwx 1 root root 0 Nov 7 18:07 physical_node ->
../../../../pci0000:00/0000:00:14.0
drwxr-xr-x 2 root root 0 Nov 7 18:07 power
lrwxrwxrwx 1 root root 0 Nov 7 18:05 subsystem -> ../../../../../bus/acpi
-rw-r--r-- 1 root root 4096 Nov 7 18:05 uevent
drwxr-xr-x 3 root root 0 Nov 7 18:05 wakeup
$ ls -l /sys/bus/acpi/devices/device\:25/physical_node/
total 0
-r--r--r-- 1 root root 4096 Nov 7 18:07 ari_enabled
-rw-r--r-- 1 root root 4096 Nov 7 18:07 broken_parity_status
-r--r--r-- 1 root root 4096 Nov 7 18:05 class
-rw-r--r-- 1 root root 256 Nov 7 18:07 config
-r--r--r-- 1 root root 4096 Nov 7 18:07 consistent_dma_mask_bits
-rw-r--r-- 1 root root 4096 Nov 7 18:07 d3cold_allowed
-r--r--r-- 1 root root 4096 Nov 7 18:05 device
-r--r--r-- 1 root root 4096 Nov 7 18:07 dma_mask_bits
lrwxrwxrwx 1 root root 0 Nov 7 18:05 driver ->
../../../bus/pci/drivers/piix4_smbus
-rw-r--r-- 1 root root 4096 Nov 7 18:07 driver_override
-rw-r--r-- 1 root root 4096 Nov 7 18:07 enable
lrwxrwxrwx 1 root root 0 Nov 7 18:07 firmware_node ->
../../LNXSYSTM:00/LNXSYBUS:00/PNP0A08:00/device:25
drwxr-xr-x 4 root root 0 Nov 7 18:05 i2c-7
drwxr-xr-x 4 root root 0 Nov 7 18:05 i2c-8
drwxr-xr-x 4 root root 0 Nov 7 18:05 i2c-9
lrwxrwxrwx 1 root root 0 Nov 7 18:07 iommu -> ../0000:00:00.2/iommu/ivhd3
lrwxrwxrwx 1 root root 0 Nov 7 18:07 iommu_group ->
../../../kernel/iommu_groups/58
-r--r--r-- 1 root root 4096 Nov 7 18:07 irq
drwxr-xr-x 2 root root 0 Nov 7 18:07 link
-r--r--r-- 1 root root 4096 Nov 7 18:07 local_cpulist
-r--r--r-- 1 root root 4096 Nov 7 18:07 local_cpus
-r--r--r-- 1 root root 4096 Nov 7 18:07 modalias
-rw-r--r-- 1 root root 4096 Nov 7 18:07 msi_bus
-rw-r--r-- 1 root root 4096 Nov 7 18:07 numa_node
drwxr-xr-x 2 root root 0 Nov 7 18:07 power
-r--r--r-- 1 root root 4096 Nov 7 18:07 power_state
--w--w---- 1 root root 4096 Nov 7 18:07 remove
--w------- 1 root root 4096 Nov 7 18:07 rescan
-r--r--r-- 1 root root 4096 Nov 7 18:05 resource
-r--r--r-- 1 root root 4096 Nov 7 18:07 revision
lrwxrwxrwx 1 root root 0 Nov 7 18:05 subsystem -> ../../../bus/pci
-r--r--r-- 1 root root 4096 Nov 7 18:07 subsystem_device
-r--r--r-- 1 root root 4096 Nov 7 18:07 subsystem_vendor
-rw-r--r-- 1 root root 4096 Nov 7 18:05 uevent
-r--r--r-- 1 root root 4096 Nov 7 18:05 vendor
```
Maybe I need to modify ACPI code somehow to create these
'physical_nodesX' folders for the relevant i2c-7/8/9 buses?
Any feedback is appreciated.
Best regards,
Konstantin Aladyshev
