Hi, On Thu, Sep 23, 2021 at 04:17:13PM +0200, Florian Eckert wrote: > I am working wit OpenWrt which has recently switched the kernel version > from 5.4 to 5.10 on x86 Target [1] in its master branch. > > I am using a APU3 board from PC-Engine [2]. > > The APU3 board has an SMBus [3] device (Intel PIIX4 and compatible > (ATI/AMD/Serverworks/Broadcom/SMSC) to communicate with additional connected > I2C devices. > > On This SMBus there is a IO expander from microchip connect [4] via the > SMBus (i2c). > I used this microchip IO expander to control additional LEDs, as the APU3 > only has 3. > > So far, everything has worked fine, because I had wirten a platform device > for this. > Everything was recognized and compiled cleanly and I could control the LEDs > from the user-land. > > Due to the following change [5] between 5.4 and 5.10 by removing the > platform data support in > the IO expander mcp23s08, my plaform device does not compile anymore, > I can no longer use the platform device pattern for this kind of device. > > The only possibility I can think of now is to make this device known > to the kernel via a dynamic ACPI SSDT table. I have already tried various > things but I can't get the driver [4] to feel responsible for this device. > > I have used the following links that were provided by "Andy Shevchenko" to > me > to understand the concept begind ACPI SSDT handling. Thanks for that. > > https://connect.linaro.org/resources/lvc21f/lvc21f-304/ > https://www.youtube.com/watch?v=nlKjUAv3RL0&ab_channel=OSDNConf > https://stackoverflow.com/questions/65727454/ > https://stackoverflow.com/questions/60105101/ > https://stackoverflow.com/questions/54768841/ > https://stackoverflow.com/questions/46095840/ > https://github.com/westeri/meta-acpi/tree/master/recipes-bsp/acpi-tables/samples/ > > This is my aml file that I tried with. It loads but nothing happens. > > DefinitionBlock ("mcp23s08.aml", "SSDT", 5, "", "IO", 2) > { > External (\_SB.PCI0.SBUS, DeviceObj) > > Device (\_SB.PCI0.SBUS.BUS0) > { > Name (_CID, "smbus") > NAME (_ADR, Zero) > Device (PIN) > { > Name (_HID, "PRP0001") > Name (_DDN, "io expander") > Name (_CRS, ResourceTemplate () { > I2cSerialBus ( > 0x24, // Bus address > ControllerInitiated, // Don't care > 400000, // Fast mode (400 kHz) > AddressingMode7Bit, // 7-bit addressing > "\\_SB.PCI0.SBUS.BUS0", // I2C host controller > 0 // Must be 0 > ) > }) > > Name (_DSD, Package () { > ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"), > Package () { > Package () { "compatible", Package () { > "microchip,mcp23017" } }, > } > }) > } > } > } > > In Coreboot the SMBus named SBUS and is on address 0x0014000 [7]. > > But I'm not sure if that's right at all. > Somehow I don't understand how the io expander is connected to SMBus. > According to my research, however, it should fit. > > The SMBus device driver i2c-piix4 creates 3 I2C devices: > ls -la /sys/bus/i2c/devices/ > ../../../devices/pci0000:00/0000:00:14.0/i2c-0 (SMBus PIIX4 adapter port 0 > at 0b00) > ../../../devices/pci0000:00/0000:00:14.0/i2c-1 (SMBus PIIX4 adapter port 2 > at 0b00) > ../../../devices/pci0000:00/0000:00:14.0/i2c-2 (SMBus PIIX4 adapter port 1 > at 0b20) > > > The mcp23s08 is connected to the i2c-0 with address 0x24 > > Therefore I believe the following applies > > +------+ +------+ > | PCI0 |--->| SMB0 |--> i2c client A (0x24) > | | | | > +------+ +------+ > > > I have enabled the following kernel config parameters for ACPI SSDT: > CONFIG_ACPI_CUSTOM_METHOD > CONFIG_CONFIGFS_FS > CONFIG_ACPI_CONFIGFS > CONFIG_ACPI_DEBUG How do you load the SSDT? Via initrd or something else? You may need to enable CONFIG_ACPI_TABLE_UPGRADE too. Also do you see in dmesg that the SSDT is loaded? Then I suggest checking the below attributes: ../../../devices/pci0000:00/0000:00:14.0/firmware_node/path ../../../devices/pci0000:00/0000:00:14.0/i2c-0/firmware_node/path
