Re: Add a SSDT ACPI description to recognize my I2C device connected via SMBus

Florian Eckert
2021-09-29T22:40:51Z

> The mcp23s08 can not be connected to I2C. It's a SPI device.
> Which chip do you actually have? I believe it's MCP23017 or MCP23018,
> which is I2C.

Yes the device is a mcp23017, but the driver is the pinctrl_mcp23s08 [1]

root@dev ~ # lsmod | grep mcp
pinctrl_mcp23s08 16384 0
regmap_core 45056 1 pinctrl_mcp23s08,[permanent]

> Summary:
> 1) _CID notation is wrong in ASL;

I got it

> 2) driver seems supports the _ADR schema which you have used in ASL;

This refers to the i2c-0, doesn't it?
My mcp23s08 device is located at the i2c-0 on address 0x24.

> 3) something fishy about I/O addresses in the sysfs (is it a typo when
> you composed the email?);

No

I have asked myself the same question.
Something is not right.
There was a change regarding the Hudson2 in the driver, maybe something
went wrong [2]?

> 4) it's unclear what you did with ASL to get it loaded;

On my development device I did a `iasl dsl/mcp23017.dsl`
Of the following dsl

$ cat dsl/mcp23017.dsl
DefinitionBlock ("mcp23017.aml", "SSDT", 5, "", "MCP23017", 4)
{
External (\_SB.PCI0.SBUS, DeviceObj)

Scope (\_SB.PCI0.SBUS)
{
Device (GPIO)
{
Name (_HID, "PRP0001")
Name (_DDN, "MCP23017 gpio expander")
Name (_ADR, Zero)
Name (_CRS, ResourceTemplate () {
I2cSerialBus (
0x24, // Bus address
ControllerInitiated, // Don't care
400000, // Fast mode (400 kHz)
AddressingMode7Bit, // 7-bit addressing
"\\_SB.PCI0.SBUS", // I2C host controller
0 // Must be 0
)
})

Name (_DSD, Package () {
ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
Package () {
Package () { "compatible", Package () {
"microchip,mcp23017" } },
}
})
}
}
}

After that I copied this to my APU3 Target and executed
the following commands:
mkdir /sys/kernel/config/acpi/table/mcp23017

cat mcp23s08.aml > /sys/kernel/config/table/mcp23017

> 5) as Mika suggested, have you checked the kernel configuration?

I have now switched on the suggested option
CONFIG_ACPI_CUSTOM_METHOD=y
CONFIG_ACPI_TABLE_UPGRADE=y
CONFIG_CONFIGFS_FS=y
CONFIG_ACPI_CONFIGFS=y
CONFIG_ACPI_DEBUG=y

But this did not solved my issue loading ssdt during runtime.

The output of the aml on the target:

cat /sys/kernel/config/acpi/table/mcp23017/aml
SSDTsMCP23017INTL \/_SB_PCI0SBUSK
\/_SB_PCI0SBUS[H
MCP23017 gpio expande_AD_CRS&
#$\_SB.PCI0.SBUS_DSD?
microchip,mcp23017

My iasl version:

iasl --version
Illegal option: --

Intel ACPI Component Architecture
ASL+ Optimizing Compiler/Disassembler version 20181213
Copyright (c) 2000 - 2018 Intel Corporation

What else can I do?
The initrd option does not work with OpenWrt.
Maybe I can get further if you can give me a good HEX for debug_level
and the debug_layer?

---
Regards Florian

[1]
https://github.com/torvalds/linux/blob/master/drivers/pinctrl/pinctrl-mcp23s08_i2c.c
[2]
https://github.com/torvalds/linux/commit/528d53a1592b0e27c423f7cafc1df85f77fc1163#diff-aa95f6311d1fcc4d85955b153a2510e853807546ac8e0d3aa0310ac30d236147