[PATCH v2 0/3] PCI / ACPI: Handle sibling devices sharing power resources

Mika Westerberg
2019-06-18T16:19:02Z

Hi all,

Based on a discussion regarding patch series I sent previously [1] to deal
with sibling devices sharing ACPI power resources, I prepared a new
reworked version according to the comments I got.

To summarize, in Intel Ice Lake the Thunderbolt controller, PCIe root ports
and xHCI all share power resources. When they are all in D3hot power
resources (returned by _PR3) can be turned off powering off the whole
block. However, there are two issues around this.

Firstly the PCI core sets the device power state by asking what the real
ACPI power state is. This results that all but last device sharing the
power resources are in D3hot when the power resources are turned off. This
causes issues if user runs for example 'lspci' because the device is really
in D3cold so what user gets back is all ones (0xffffffff).

Secondly if any of the device is runtime resumed the power resources are
turned on bringing all other devices sharing the resources to
D0uninitialized losing their wakeup configuration.

This series aims to fix the two issues by:

1. Using the ACPI cached power state when PCI devices are transitioned
into low power states instead of reading back the "real" power state.

2. Introducing concept of "_PR0 dependent devices" that get runtime
resumed whenever their power resource (which they might share with
other sibling devices) gets turned on.

The series is based on the idea of Rafael J. Wysocki <rafael@kernel.org>.

[1] https://www.spinics.net/lists/linux-pci/msg83583.html

Mika Westerberg (3):
PCI / ACPI: Use cached ACPI device state to get PCI device power state
ACPI / PM: Introduce concept of a _PR0 dependent device
PCI / ACPI: Add _PR0 dependent devices

drivers/acpi/power.c | 139 ++++++++++++++++++++++++++++++++++++++++
drivers/pci/pci-acpi.c | 5 +-
include/acpi/acpi_bus.h | 4 ++
3 files changed, 147 insertions(+), 1 deletion(-)

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2.20.1