ACK: [PATCH 0/1][SRU][oem-5.14/impish/jammy] AMD Cezanne/Barcelo taking cores offline causes S0i3 failures

[Tim Gardner]

Acked-by: Tim Gardner <tim.gardner at canonical.com>

On 12/15/21 9:40 AM, You-Sheng Yang wrote:
> BugLink: https://bugs.launchpad.net/bugs/1954930
> 
> [Impact]
> 
> Detailed in https://gitlab.freedesktop.org/drm/amd/-/issues/1708, taking
> some cpu cores offline using cpufreq gadgets or via sysfs may hang the
> system.
> 
> [Fix]
> 
> In v5.16-rc1 commit d6b88ce2eb9d ("ACPI: processor idle: Allow playing
> dead in C3 state") fixes this issue.
> 
> [Test Case]
> 
> As stated in aforementioned bug url, setup cpufreq extention to take
> down a few cpu cores, and trigger system suspend. There are ~50% chances
> that networking/input/... would hang and the user can only reboot by
> sysrq keys.
> 
> [Where problems could occur]
> 
> According to the patch discussion thread in
> https://lore.kernel.org/linux-acpi/20210922133116.102-1-richard.gong@amd.com/,
> the limitation to allow enter_dead in no more than ACPI_STATE_C2 might
> not have a practical meaning, but simply C2 was the deepest supported
> then.
> 
> [Other Info]
> 
> While this is currently only available in v5.16-rc1 and affects AMD
> Cezanne/Barcelo, oem-5.14/impish and jammy are nominated.
> 
> Richard Gong (1):
>    ACPI: processor idle: Allow playing dead in C3 state
> 
>   drivers/acpi/processor_idle.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 

-- 
-----------
Tim Gardner
Canonical, Inc