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e65cb01134
The _CRS resources in many cases want to have ResourceSource field
to be a type of ACPI String. This means that to compile properly
we need to enclosure the name path into double quotes. This will
in practice defer the interpretation to a run-time stage, However,
this may be interpreted differently on different OSes and ACPI
interpreter implementations. In particular ACPICA might not correctly
recognize the leading '^' (caret) character and will not resolve
the relative name path properly. On top of that, this piece may be
used in SSDTs which are loaded after the DSDT and on itself may also
not resolve relative name paths outside of their own scopes.
With this all said, fix documentation to use fully-qualified name
paths always to avoid any misinterpretations, which is proven to
work.
Fixes: 8eb5c87a92 ("i2c: add ACPI support for I2C mux ports")
Reported-by: Yevhen Kondrashyn <e.kondrashyn@gmail.com>
Cc: All applicable <stable@vger.kernel.org>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://patch.msgid.link/20250710170225.961303-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
61 lines
1.7 KiB
ReStructuredText
61 lines
1.7 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0
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==============
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ACPI I2C Muxes
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==============
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Describing an I2C device hierarchy that includes I2C muxes requires an ACPI
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Device () scope per mux channel.
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Consider this topology::
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+------+ +------+
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| SMB1 |-->| MUX0 |--CH00--> i2c client A (0x50)
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| | | 0x70 |--CH01--> i2c client B (0x50)
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+------+ +------+
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which corresponds to the following ASL (in the scope of \_SB)::
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Device (SMB1)
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{
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Name (_HID, ...)
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Device (MUX0)
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{
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Name (_HID, ...)
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Name (_CRS, ResourceTemplate () {
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I2cSerialBus (0x70, ControllerInitiated, I2C_SPEED,
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AddressingMode7Bit, "\\_SB.SMB1", 0x00,
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ResourceConsumer,,)
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}
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Device (CH00)
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{
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Name (_ADR, 0)
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Device (CLIA)
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{
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Name (_HID, ...)
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Name (_CRS, ResourceTemplate () {
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I2cSerialBus (0x50, ControllerInitiated, I2C_SPEED,
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AddressingMode7Bit, "\\_SB.SMB1.CH00", 0x00,
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ResourceConsumer,,)
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}
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}
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}
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Device (CH01)
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{
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Name (_ADR, 1)
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Device (CLIB)
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{
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Name (_HID, ...)
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Name (_CRS, ResourceTemplate () {
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I2cSerialBus (0x50, ControllerInitiated, I2C_SPEED,
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AddressingMode7Bit, "\\_SB.SMB1.CH01", 0x00,
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ResourceConsumer,,)
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}
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}
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}
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}
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}
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