ACPI: scan: Defer device power initialization

acpi_bus_get_power_flags() initializes the device power state while the
ACPI device object is being created, before checking whether the device
is ready for enumeration.

If enumeration is deferred, acpi_bus_attach() clears the initialized and
power_manageable flags. When the dependency is later satisfied,
acpi_bus_init_power() is called again and takes additional references to
the power resources used by the device. These references prevent the
resources from being turned off when the device enters D3.

This issue was reproduced on a SpacemiT K3 RISC-V Pico-ITX. The affected
device uses a power resource through _PR0 and has an automatically
derived dependency on its interrupt controller.

The initial power initialization acquires a power resource reference.
The device is then deferred, but that reference is not dropped. When
the dependency becomes available, power initialization acquires another
reference. Consequently, entering D3 only drops the reference count
from 2 to 1 and _OFF is not evaluated:

 [    0.314611] ACPI Debug:  "I2P2 _STA"
 [    0.318260] ACPI: \_SB_.I2P2: ACPI: PM: Power resource is on
 [    0.323998] ACPI: \_SB_.I2P2: New power resource
 [    0.382108] ACPI Debug:  "I2P2 _STA"
 [    0.478964] ACPI Debug:  "I2P2 _ON"
 [    0.482498] ACPI: \_SB_.I2P2: ACPI: PM: Power resource turned on
 [    0.488597] ACPI Debug:  "I2C2, PS0"
 [    0.863170] ACPI: \_SB_.I2P2: ACPI: PM: Power resource already on
 [    0.873686] ACPI Debug:  "I2C2, PS0"
 [    2.416055] ACPI Debug:  "I2C2, PS3"
 [    2.423397] ACPI: \_SB_.I2P2: ACPI: PM: Power resource still in use

To address this, remove the early acpi_bus_init_power() call and leave
regular ACPI device objects uninitialized until acpi_bus_attach() runs
after the device is ready for enumeration.

Power resource objects are initialized through acpi_add_power_resource()
and do not require the generic initialization in acpi_bus_attach(), so
mark them as initialized there.

After the change, device power state initialization is deferred until its
dependency is met. Since no reference is acquired before then, the power
resource left on by firmware is turned off as unused after the namespace
scan. Once the dependency is met, the resource is turned on once for the
device and is turned off normally when the device later enters D3:

 [    0.314628] ACPI Debug:  "I2P2 _STA"
 [    0.318277] ACPI: \_SB_.I2P2: ACPI: PM: Power resource is on
 [    0.324016] ACPI: \_SB_.I2P2: New power resource
 [    0.382118] ACPI Debug:  "I2P2 _STA"
 [    0.496116] ACPI: \_SB_.I2P2: ACPI: PM: Turning OFF
 [    0.501081] ACPI Debug:  "I2P2 _OFF"
 [    0.504705] ACPI: \_SB_.I2P2: ACPI: PM: Power resource turned off
 [    1.415899] ACPI Debug:  "I2P2 _ON"
 [    1.418866] ACPI: \_SB_.I2P2: ACPI: PM: Power resource turned on
 [    1.424947] ACPI Debug:  "I2C2, PS0"
 [    2.647655] ACPI Debug:  "I2C2, PS3"
 [    2.654856] ACPI Debug:  "I2P2 _OFF"
 [    2.654866] ACPI: \_SB_.I2P2: ACPI: PM: Power resource turned off

This also avoids powering up devices before their dependencies are
available.

Signed-off-by: Peixin Xie <peixin.xie@linux.spacemit.com>
[ rjw: Changelog edits ]
Link: https://patch.msgid.link/20260820-acpi-power-resource-ref-fix-v2-1-29818173ea13@linux.spacemit.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

0 files changed, 0 insertions, 0 deletions