ACK: [PATCH 0/2][SRU][impish/OEM-5.14] NVMe devices fail to probe due to ACPI power state change

[Zachary Tahenakos]

Acked-by: Zachary Tahenakos <zachary.tahenakos at canonical.com>

On 4/13/22 12:50 PM, Heitor Alves de Siqueira wrote:
> BugLink: https://bugs.launchpad.net/bugs/1942624
>
> Hi kernel-team,
>
> Users have reported specific NVMe disks failing to probe due to a power
> management regression in ACPI. Our affected kernels include 5.13 (impish) and
> 5.14 (focal-oem). For the impish kernel, there's an additional dependency patch
> that has reworked how unused resources are turned off.
>
> I've provided test builds of the affected kernels to the Launchpad bug and to
> some affected users, and they've confirmed the patches fix the issues without
> noticeable regressions.
>
> [Impact]
> * Specific NVMe devices fail to probe and become unusable after boot
> * Caused by an ACPI regression that doesn't correctly handle power states
> * Upstream regression commit:
>    7e4fdeafa61f ACPI: power: Turn off unused power resources unconditionally
> * Regression window for Ubuntu includes 5.13- and 5.14-based kernels
>
> [Test Plan]
> * Boot affected kernel and validate whether NVMe device is usable
> * Check kernel logs for failed probe message:
>    "can't change power state from D3Cold to D0 (config space inaccessible)"
>
> [Fix]
> * Fixed by not turning off power resources in unknown state
> * Fix was introduced by commit:
>    bc2836859643 ACPI: PM: Do not turn off power resources in unknown state
> * Kernels starting with 5.15 (e.g. Jammy) not affected, as they already contain
>    the fix above
>
> [Regression Potential]
> * NVMe devices continue failing to probe
> * Other devices become unusable after power state changes
> * Further regressions would affect power state of devices, possibly after boot
>
> Rafael J. Wysocki (2):
>    ACPI: power: Rework turning off unused power resources
>    ACPI: PM: Do not turn off power resources in unknown state
>
>   drivers/acpi/internal.h |  2 +-
>   drivers/acpi/power.c    | 47 ++++++++++++-----------------------------
>   drivers/acpi/scan.c     |  2 +-
>   drivers/acpi/sleep.c    |  2 +-
>   4 files changed, 17 insertions(+), 36 deletions(-)
>