Re: [PATCH v2 0/2] soc: aspeed: ipmi: add KCS Channel 4 over PCIe

[YC Hsieh]

> The PCIe-to-LPC bridge on the AST2600 exposes 4 channels, matching the LPC
> controller's own KCS1-4, not just channel 4.
> It would be better If you can provide a way to handle multiple LPC controller for
> kcs channels.

I raised an RFC to discuss support for multiple LPC controllers in [1].

Perhaps we should first take other people's opinions into consideration
before moving forward.

[1] https://lkml.org/lkml/2026/7/23/429

> >
> > 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 [2] 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.
> > ...
> > ```
> >
> > The original patch [1] review set to use the existing LPC bus and modify the
> > kcs_bmc_aspeed driver.
> >
> > [1]
> > https://lore.kernel.org/linux-aspeed/de49f2032f5b1f170161dcd6191c0daa48f0
> > b0c2.1784117715.git.gregoire.layet@xxxxxxxxxxxxx/
> > [2]
> > https://lore.kernel.org/linux-aspeed/51e455417bdcfe608270c6cb2806b1fd971f
> > b998.1783524645.git.gregoire.layet@xxxxxxxxxxxxx/
> >
> > 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 |  7 +++++
> >  drivers/char/ipmi/kcs_bmc_aspeed.c      | 39
> > +++++++++++++++++++++++--
> >  2 files changed, 44 insertions(+), 2 deletions(-)
> >
> >
> > base-commit: 03f906d8f5541e8bb741035981304feceed5993d
> > --
> > 2.54.0