On Mon, Nov 11, 2024 at 05:02:31PM +0300, Konstantin Aladyshev wrote:
> diff --git a/Documentation/i2c/busses/i2c-piix4.rst b/Documentation/i2c/busses/i2c-piix4.rst
> index 07fe6f6f4b18..90447dff7419 100644
> --- a/Documentation/i2c/busses/i2c-piix4.rst
> +++ b/Documentation/i2c/busses/i2c-piix4.rst
> @@ -109,3 +109,65 @@ which can easily get corrupted due to a state machine bug. These are mostly
> Thinkpad laptops, but desktop systems may also be affected. We have no list
> of all affected systems, so the only safe solution was to prevent access to
> the SMBus on all IBM systems (detected using DMI data.)
> +
> +
> +Description in the ACPI code
> +----------------------------
> +
> +Device driver for the PIIX4 chip creates a separate I2C bus for each of its ports::
> +
> + $ i2cdetect -l
> + ...
> + i2c-7 unknown SMBus PIIX4 adapter port 0 at 0b00 N/A
> + i2c-8 unknown SMBus PIIX4 adapter port 2 at 0b00 N/A
> + i2c-9 unknown SMBus PIIX4 adapter port 1 at 0b20 N/A
> + ...
> +
> +Therefore if you want to access one of these busses in the ACPI code, port subdevices
> +are needed to be declared inside the PIIX device::
> +
> + Scope (\_SB_.PCI0.SMBS)
> + {
> + Name (_ADR, 0x00140000)
> +
> + Device (SMB0) {
> + Name (_ADR, 0)
> + }
> + Device (SMB1) {
> + Name (_ADR, 1)
> + }
> + Device (SMB2) {
> + Name (_ADR, 2)
> + }
> + }
> +
> +If it is not the case for your UEFI firmware and you don't have access to the source
> +code, you can use ACPI SSDT Overlays to provide the missing parts. Just keep in mind
> +that in this case you would need to load your extra SSDT table before the piix4 driver
> +start, i.e. you should provide SSDT via initrd or EFI variable methods and not via
> +configfs.
> +
> +As an example of usage here is the ACPI snippet code that would assign jc42 driver
> +to the 0x1C device on the I2C bus created by the PIIX port 0::
> +
> + Device (JC42) {
> + Name (_HID, "PRP0001")
> + Name (_DDN, "JC42 Temperature sensor")
> + Name (_CRS, ResourceTemplate () {
> + I2cSerialBusV2 (
> + 0x001c,
> + ControllerInitiated,
> + 100000,
> + AddressingMode7Bit,
> + "\\_SB.PCI0.SMBS.SMB0",
> + 0
> + )
> + })
> +
> + Name (_DSD, Package () {
> + ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
> + Package () {
> + Package () { "compatible", Package() { "jedec,jc-42.4-temp" } },
> + }
> + })
> + }
Looks good, thanks!
Reviewed-by: Bagas Sanjaya <bagasdotme@xxxxxxxxx>
--
An old man doll... just what I always wanted! - Clara
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