Re: [PATCH] platform/x86: amd-pmc: Set QOS during suspend on CZN w/ timer wakeup

[Greg KH <gregkh@linuxfoundation.org>]

On Mon, Feb 28, 2022 at 10:15:10PM -0600, Mario Limonciello wrote:
> commit 59348401ebed ("platform/x86: amd-pmc: Add special handling for
> timer based S0i3 wakeup") adds support for using another platform timer
> in lieu of the RTC which doesn't work properly on some systems. This path
> was validated and worked well before submission. During the 5.16-rc1 merge
> window other patches were merged that caused this to stop working properly.
> 
> When this feature was used with 5.16-rc1 or later some OEM laptops with the
> matching firmware requirements from that commit would shutdown instead of
> program a timer based wakeup.
> 
> This was bisected to commit 8d89835b0467 ("PM: suspend: Do not pause
> cpuidle in the suspend-to-idle path").  This wasn't supposed to cause any
> negative impacts and also tested well on both Intel and ARM platforms.
> However this changed the semantics of when CPUs are allowed to be in the
> deepest state. For the AMD systems in question it appears this causes a
> firmware crash for timer based wakeup.
> 
> It's hypothesized to be caused by the `amd-pmc` driver sending `OS_HINT`
> and all the CPUs going into a deep state while the timer is still being
> programmed. It's likely a firmware bug, but to avoid it don't allow setting
> CPUs into the deepest state while using CZN timer wakeup path.
> 
> If later it's discovered that this also occurs from "regular" suspends
> without a timer as well or on other silicon, this may be later expanded to
> run in the suspend path for more scenarios.
> 
> Cc: stable@vger.kernel.org # 5.16+
> Suggested-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> Link: https://lore.kernel.org/linux-acpi/BL1PR12MB51570F5BD05980A0DCA1F3F4E23A9@BL1PR12MB5157.namprd12.prod.outlook.com/T/#mee35f39c41a04b624700ab2621c795367f19c90e
> Fixes: 8d89835b0467 ("PM: suspend: Do not pause cpuidle in the suspend-to-idle path")
> Fixes: 23f62d7ab25b ("PM: sleep: Pause cpuidle later and resume it earlier during system transitions")
> Fixes: 59348401ebed ("platform/x86: amd-pmc: Add special handling for timer based S0i3 wakeup"
> Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
> Link: https://lore.kernel.org/r/20220223175237.6209-1-mario.limonciello@amd.com
> Reviewed-by: Hans de Goede <hdegoede@redhat.com>
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
> (cherry picked from commit 68af28426b3ca1bf9ba21c7d8bdd0ff639e5134c)
> ---
> This didn't apply cleanly to 5.16.y because 5.16.y doesn't contain the STB
> feature.  Manually fixed up the commit for this.
> This is *only* intended for 5.16.

Now queued up, thanks.

greg k-h