Re: [PATCH v3 0/3] PCI / ACPI: Handle sibling devices sharing power resources

["Rafael J. Wysocki" <rafael@kernel.org>]

On Tue, Jun 25, 2019 at 12:30 PM Mika Westerberg
<mika.westerberg@linux.intel.com> wrote:
>
> Hi all,
>
> This is third iteration of the patch series addressing issues around
> sibling PCI devices sharing ACPI power resources.
>
> As a concrete example in Intel Ice Lake the Thunderbolt controller, PCIe
> root ports and xHCI all share the same ACPI 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>.
>
> Previous version of the series can be found here:
>
>   v2: https://lore.kernel.org/linux-pci/20190618161858.77834-1-mika.westerberg@linux.intel.com/T/#m7a41d0b745400054543324ce84125040dbfed912
>   v1: https://www.spinics.net/lists/linux-pci/msg83583.html
>
> Changes from v2:
>
>   * Updated changelog of patch [1/3] according to comments I got. I left
>     the D3C power resource and xHCI there because it shows that we can have
>     multiple shared power resources.
>
>   * Added link to the discussion around v2.
>
>   * Use adev->flags.power_manageable in patch [2/3].
>
> 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    | 135 ++++++++++++++++++++++++++++++++++++++++
>  drivers/pci/pci-acpi.c  |   5 +-
>  include/acpi/acpi_bus.h |   4 ++
>  3 files changed, 143 insertions(+), 1 deletion(-)
>

The whole series looks good to me, thank you!