[PATCH v3 0/2] ipmi: kcs_bmc_aspeed: g6: Add KCS Channel 4 over PCIe

The ASPEED AST2600 has a PCIe to LPC controller. It includes a KCS
interface on channel 4. This is a fully KCS-compatible interface
that is exposed over PCIe.

Add pcie_kcs4 to existing LPC bus in aspeed-g6.dtsi.
Modify kcs_bmc_aspeed driver to detect the PCIe over LPC channel.

In the driver, this PCIe over LPC channel will be detected as Channel 5.
In the datasheet this is defined as Channel 4 over PCIe.

The Channel 4 name is still referenced in the offsets macros.

The host need a driver to activate the MSI interrupts with the PCIe BMC
Device.

Tests:
With the patch [1] adding PCIe BMC device for Virtual UART, the MSI
interrupts are correctly setups. The Host driver is build and side
loaded on the host. The ipmi_si driver on the host is loaded manually
with the KCS address given by hand. 'ipmitool mc info' is run to confirm
it's working.

Tested on : Asus IPMI Expansion Card, AST2600.

$ insmod aspeed-host-bmc-dev.ko
$ lspci -vvv -d 1a03:2402
02:01.0 Unassigned class [ff00]: ASPEED Technology, Inc. Device 2402
	Subsystem: ASPEED Technology, Inc. Device 2402
	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-
	Latency: 0
	Interrupt: pin A routed to IRQ 154
	IOMMU group: 12
	Region 0: Memory at 82080000 (32-bit, non-prefetchable) [size=4K]
	Region 1: Memory at 82040000 (32-bit, non-prefetchable) [size=256K]
	Capabilities: [40] Power Management version 3
		Flags: PMEClk- DSI- D1+ D2+ AuxCurrent=375mA PME(D0+,D1+,D2+,D3hot+,D3cold+)
		Status: D0 NoSoftRst- PME-Enable- DSel=0 DScale=0 PME-
	Capabilities: [50] MSI: Enable+ Count=32/32 Maskable- 64bit+
		Address: 00000000fee00818  Data: 0000
	Kernel driver in use: aspeed-host-bmc-dev

$ modprobe ipmi_si type=kcs addrs=0x82040E88 regspacings=4 regsizes=1 regshifts=0

$ ipmitool mc info
Device ID                 : 32
Device Revision           : 1
Firmware Revision         : 26.04
IPMI Version              : 2.0
Manufacturer ID           : 2623
Manufacturer Name         : ASUSTek Computer Inc.
...

Changes since v2 [2]:
 - Put pcie_kcs4 node in ascending address order.
 - Add missing "case PCIE_LPC_ODR4" in aspeed_kcs_outb.

An RFC [3] is in discussion for implementing multiple LPC controller support
in kcs_bmc_aspeed. This would change the implementation of the pcie_lpc.
This series adds the pcie_kcs4 to have devices like the Asus IPMI Expansion Card
use it, before waiting to have full PCIe LPC support.

[1] https://lore.kernel.org/linux-aspeed/51e455417bdcfe608270c6cb2806b1fd971fb998.1783524645.git.gregoire.layet@9elements.com/ (local)
[2] https://lore.kernel.org/linux-aspeed/cover.1784732161.git.gregoire.layet@9elements.com/ (local)
[3] https://lkml.org/lkml/2026/7/23/429

Grégoire Layet (2):
  ipmi: kcs_bmc_aspeed: g6: Add KCS Channel 4 over PCIe
  ARM: dts: aspeed-g6: add pcie-kcs4

 arch/arm/boot/dts/aspeed/aspeed-g6.dtsi |  8 +++++
 drivers/char/ipmi/kcs_bmc_aspeed.c      | 41 +++++++++++++++++++++++--
 2 files changed, 47 insertions(+), 2 deletions(-)


base-commit: 03f906d8f5541e8bb741035981304feceed5993d
--
2.54.0