Re: [PATCH v2] PCI: Don't assume root ports from > 2015 are power manageable

[Mika Westerberg <mika.westerberg@linux.intel.com>]

Hi Mario,

On Wed, May 17, 2023 at 10:08:27AM -0500, Mario Limonciello wrote:
> Using an XHCI device to wakeup the system from s2idle fails when
> that XHCI device is connected to a USB-C port for an AMD USB4
> router.
> 
> Due to commit 9d26d3a8f1b0 ("PCI: Put PCIe ports into D3 during
> suspend") all root port go into D3 during s2idle.
> When the root ports are in D3 over s2idle it's not possible for the
> platform firmware to properly identify the wakeup source.
> 
> Comparing registers between Linux and Windows 11 this behavior to put root
> ports into D3 at suspend is unique to Linux.  On an affected system
> Windows does not put the root ports into D3 over Modern Standby.
> 
> Windows doesn't put the root ports into D3 because root ports are not
> power manageable; they're missing _PRW and _S0W.
> 
> Linux shouldn't be assuming they support D3 just because they're newer
> than 2015, the ports should also be deemed power manageable.
> Add an extra check for this to ensure D3 isn't selected for such machines.
> 
> Fixes: 9d26d3a8f1b0 ("PCI: Put PCIe ports into D3 during suspend")
> Reported-by: Iain Lane <iain@orangesquash.org.uk>
> Closes: https://forums.lenovo.com/t5/Ubuntu/Z13-can-t-resume-from-suspend-with-external-USB-keyboard/m-p/5217121
> Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
> ---
>  drivers/pci/pci.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 5ede93222bc1..3fe27aef09e6 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -3010,6 +3010,9 @@ bool pci_bridge_d3_possible(struct pci_dev *bridge)
>  		if (dmi_check_system(bridge_d3_blacklist))
>  			return false;
>  
> +		if (!platform_pci_power_manageable(bridge))
> +			return false;
> +

We already call platform_pci_bridge_d3() few lines up. That function
should know whether "platform" supports D3 for the bridges, and I think
it actually calls acpi_device_power_manageable() that platform_pci_power_manageable()
ends up checking too.