[Linux I2C/SMBus] AMD FCH SMBus controller fails to bind on Gigabyte B850M FORCE WIFI6E

[Yazoudi <Yazoudi@proton.me>]

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Hello,

I am investigating an SMBus controller that does not bind to the Linux 
i2c_piix4 driver on my Gigabyte B850M FORCE WIFI6E (revision 1.0) 
motherboard.

The PCI device is detected, and i2c_piix4 is listed as a candidate 
module, but no driver is bound to the device. The kernel also logs an 
ACPI resource conflict involving the SMBus I/O range and the GSA1.SMBI 
operation region.

System details:

  *

    Motherboard: Gigabyte B850M FORCE WIFI6E, revision 1.0

  *

    BIOS: F8a

  *

    Distribution: Arch Linux with zen kernel

  *

    Kernel: 7.2.11-zen1-1-zen

  *

    SMBus PCI device: 00:14.0, AMD FCH SMBus Controller [1022:790b],
    revision 71

  *

    PCI subsystem: Gigabyte [1458:5001]

Relevant observations:

 1.

    |lspci -nnk -s 00:14.0|lists |i2c_piix4|under Kernel modules, but
    does not show a Kernel driver in use.

 2.

    |/sys/bus/pci/devices/0000:00:14.0/driver|does not resolve to a driver.

 3.

    The kernel logs:
    |ACPI Warning: SystemIO range 0x0000000000000B00-0x0000000000000B08
    conflicts with OpRegion 0x0000000000000B00-0x0000000000000B0F
    (\GSA1.SMBI)|
    followed by:
    |ACPI: OSL: Resource conflict; ACPI support missing from driver?|

 4.

    |/proc/ioports|lists |0b00-0b0f : PNP0C02:03|.

 5.

    Reloading i2c_piix4 does not bind the driver, and no SMBus adapter
    appears among the available I²C adapters.

I originally investigated this because OpenRGB cannot detect my KLEVV 
CRAS V RGB DDR5 modules. The |spd5118|driver loads, but no SPD devices 
are instantiated. I understand that SPD access and RGB control are 
separate issues; my immediate concern is the SMBus controller not binding.

I found a related patch discussion concerning an ACPI resource conflict 
on the Gigabyte X870 EAGLE WIFI7:
https://lkml.rescloud.iu.edu/2608.1/09152.html 
<https://lkml.rescloud.iu.edu/2608.1/09152.html>

That is a different motherboard, so I do not know whether the same 
underlying issue applies here.

Could you advise whether this looks like an ACPI resource reservation 
preventing i2c_piix4 from binding, and what additional diagnostics would 
help establish the cause? I have not forced the driver to bind or 
disabled the kernel's ACPI resource protections.

I can provide the full kernel log, PCI configuration, and other 
diagnostic output if needed.

Thank you.


[-- Attachment #2: diagnostics.txt --]
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=== Kernel ===
Linux YazoudiPc 7.2.11-zen1-1-zen #1 ZEN SMP PREEMPT_DYNAMIC Fri, 16 Oct 2026 00:28:42 +0000 x86_64 GNU/Linux
Linux version 7.2.11-zen1-1-zen (linux-zen@archlinux) (gcc (GCC) 16.2.1 20260810, GNU ld (GNU Binutils) 2.47) #1 ZEN SMP PREEMPT_DYNAMIC Fri, 16 Oct 2026 00:28:42 +0000

=== Distribution ===
NAME="Arch Linux"
PRETTY_NAME="Arch Linux"
ID=arch
BUILD_ID=rolling
ANSI_COLOR="38;2;23;147;209"
HOME_URL="https://archlinux.org/"
DOCUMENTATION_URL="https://wiki.archlinux.org/"
SUPPORT_URL="https://bbs.archlinux.org/"
BUG_REPORT_URL="https://gitlab.archlinux.org/groups/archlinux/-/issues"
PRIVACY_POLICY_URL="https://terms.archlinux.org/docs/privacy-policy/"
LOGO=archlinux-logo

=== Motherboard and BIOS ===
B850M FORCE WIFI6E
x.x
F8a
03/11/2026

=== SMBus PCI controller ===
00:14.0 SMBus [0c05]: Advanced Micro Devices, Inc. [AMD] FCH SMBus Controller [1022:790b] (rev 71)
	Subsystem: Gigabyte Technology Co., Ltd Device [1458:5001]
	Kernel modules: i2c_piix4, sp5100_tco
00:14.0 SMBus: Advanced Micro Devices, Inc. [AMD] FCH SMBus Controller (rev 71)
	Subsystem: Gigabyte Technology Co., Ltd Device 5001
	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-
	IOMMU group: 10
	Kernel modules: i2c_piix4, sp5100_tco


=== I/O resource reservation ===
  0000-0000 : PNP0B00:00

=== Relevant kernel messages ===
Oct 30 10:51:59 YazoudiPc kernel: BIOS-e820: [mem 0x000000000b000000-0x000000000b020fff]  device reserved
Oct 30 10:51:59 YazoudiPc kernel: PM: hibernation: Registered nosave memory: [mem 0x0b000000-0x0b020fff]
Oct 30 10:51:59 YazoudiPc kernel: e820: register RAM buffer resource [mem 0x0b000000-0x0bffffff]
Oct 30 10:51:59 YazoudiPc kernel: acpi PNP0C02:03: Reserved [io  0x0b00-0x0b0f]
Oct 30 10:51:59 YazoudiPc kernel: rtc_cmos PNP0B00:00: RTC can wake from S4
Oct 30 10:51:59 YazoudiPc kernel: rtc_cmos PNP0B00:00: registered as rtc0
Oct 30 10:51:59 YazoudiPc kernel: rtc_cmos PNP0B00:00: setting system clock to 2026-10-30T06:51:51 UTC (1793343111)
Oct 30 10:51:59 YazoudiPc kernel: rtc_cmos PNP0B00:00: alarms up to one month, y3k, 114 bytes nvram
Oct 30 10:51:59 YazoudiPc kernel: ACPI Warning: SystemIO range 0x0000000000000B00-0x0000000000000B08 conflicts with OpRegion 0x0000000000000B00-0x0000000000000B0F (\GSA1.SMBI) (20260408/utaddress-204)
Oct 30 10:51:59 YazoudiPc kernel: ACPI: OSL: Resource conflict; ACPI support missing from driver?
Oct 30 11:24:25 YazoudiPc kernel: ACPI Warning: SystemIO range 0x0000000000000B00-0x0000000000000B08 conflicts with OpRegion 0x0000000000000B00-0x0000000000000B0F (\GSA1.SMBI) (20260408/utaddress-204)
Oct 30 11:24:25 YazoudiPc kernel: ACPI: OSL: Resource conflict; ACPI support missing from driver?