Re: [PATCH v20 2/2] PCI: Add a quirk for AMD PCIe root ports w/ USB4 controllers

[Mario Limonciello <mario.limonciello@amd.com>]

On 9/25/2023 00:20, Mika Westerberg wrote:
> On Tue, Sep 19, 2023 at 10:27:24PM -0500, Mario Limonciello wrote:
>> Iain reports that USB devices can't be used to wake a Lenovo Z13
>> from suspend. This problem occurs because the PCIe root port has been put
>> into D3hot and AMD's platform can't handle the PME associated with USB
>> devices waking the platform from a hardware sleep state in this case.
>> The platform is put into a hardware sleep state by the actions of the
>> amd-pmc driver.
>>
>> Although the issue is initially reported on a single model it actually
>> affects all Yellow Carp (Rembrandt) and Pink Sardine (Phoenix) SoCs.
>> This problem only occurs on Linux specifically when attempting to
>> wake the platform from a hardware sleep state.
>> Comparing the behavior on Windows and Linux, Windows doesn't put
>> the root ports into D3 at this time.
>>
>> Linux decides the target state to put the device into at suspend by
>> this policy:
>> 1. If platform_pci_power_manageable():
>>     Use platform_pci_choose_state()
>> 2. If the device is armed for wakeup:
>>     Select the deepest D-state that supports a PME.
>> 3. Else:
>>     Use D3hot.
>>
>> Devices are considered power manageable by the platform when they have
>> one or more objects described in the table in section 7.3 of the ACPI 6.5
>> specification [1]. In this case the root ports are not power manageable.
>>
>> If devices are not considered power manageable; specs are ambiguous as
>> to what should happen.  In this situation Windows 11 puts PCIe ports
>> in D0 ostensibly due the policy from the "uPEP driver" which is a
>> complimentary driver the Linux "amd-pmc" driver.
>>
>> Linux chooses to allow D3 for these root ports due to the policy
>> introduced by commit 9d26d3a8f1b0 ("PCI: Put PCIe ports into D3 during
>> suspend"). Since Linux allows D3 for these ports, it follows the
>> assertion that a PME can be used to wake from D3hot or D3cold and selects
>> D3hot at suspend time.
>>
>> Even though the PCIe PM capabilities advertise PME from D3hot or D3cold
>> the Windows uPEP driver expresses the desired state that should be
>> selected for suspend is still D30.  As Linux doesn't use this information,
>> for makin ga policy decision introduce a quirk for the problematic root
>> ports.
>>
>> The quirk removes PME support for D3hot and D3cold at system suspend time.
>> When the port is configured for wakeup this will prevent these states
>> from being selected in pci_target_state().
>>
>> After the system is resumes the PME support is re-read from the PM
>> capabilities register to allow opportunistic power savings at runtime by
>> letting the root port go into D3hot or D3cold.
>>
>> Cc: stable@vger.kernel.org
>> Link: https://learn.microsoft.com/en-us/windows-hardware/design/device-experiences/platform-design-for-modern-standby#low-power-core-silicon-cpu-soc-dram [1]
>> 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>
> 
> Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
> 
> One super-minor comment, no need to send a new version just for this.

Much appreciated!

Bjorn,

Anything else you want to see for this series?

> 
>> ---
>> v19->v20:
>>   * Adjust commit message (Bjorn)
>>   * Use FIELD_GET (Ilpo)
>>   * Use pci_walk_bus (Lukas)
>> ---
>>   drivers/pci/quirks.c | 71 ++++++++++++++++++++++++++++++++++++++++++++
>>   1 file changed, 71 insertions(+)
>>
>> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
>> index eeec1d6f9023..4159b7f20fd5 100644
>> --- a/drivers/pci/quirks.c
>> +++ b/drivers/pci/quirks.c
>> @@ -6188,3 +6188,74 @@ DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x9a31, dpc_log_size);
>>   DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_XILINX, 0x5020, of_pci_make_dev_node);
>>   DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_XILINX, 0x5021, of_pci_make_dev_node);
>>   DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_REDHAT, 0x0005, of_pci_make_dev_node);
>> +
>> +#ifdef CONFIG_SUSPEND
>> +/*
>> + * When AMD PCIe root ports with AMD USB4 controllers attached to them are put
>> + * into D3hot or D3cold downstream USB devices may fail to wakeup the system
>> + * from suspend to idle.  This manifests as a missing wakeup interrupt.
>> + *
>> + * Prevent the associated root port from using PME to wake from D3hot or
>> + * D3cold power states during suspend.
>> + * This will effectively put the root port into D0 power state over suspend.
>> + */
>> +#define PCI_PM_CAP_D3_PME_MASK	((PCI_PM_CAP_PME_D3hot|PCI_PM_CAP_PME_D3cold) \
>> +				>> PCI_PM_CAP_PME_SHIFT)
>> +static int modify_pme_amd_usb4(struct pci_dev *dev, void *data)
>> +{
>> +	bool *suspend = (bool *)data;
> 
> You could also pass the bool as value because void * can hold it so
> 
> 	bool suspend = (bool)data;
> 
>> +	struct pci_dev *rp;
>> +	u16 pmc;
>> +
>> +	if (dev->vendor != PCI_VENDOR_ID_AMD ||
>> +	    dev->class != PCI_CLASS_SERIAL_USB_USB4)
>> +		return 0;
>> +	rp = pcie_find_root_port(dev);
>> +	if (!rp->pm_cap)
>> +		return -ENODEV;
>> +
>> +	if (*suspend) {
>> +		if (!(rp->pme_support & PCI_PM_CAP_D3_PME_MASK))
>> +			return -EINVAL;
>> +
>> +		rp->pme_support &= ~PCI_PM_CAP_D3_PME_MASK;
>> +		dev_info_once(&rp->dev, "quirk: disabling PME from D3hot and D3cold at suspend\n");
>> +
>> +		/* no need to check any more devices, found and applied quirk */
>> +		return -EEXIST;
>> +	}
>> +
>> +	/* already done */
>> +	if (rp->pme_support & PCI_PM_CAP_D3_PME_MASK)
>> +		return -EINVAL;
>> +
>> +	/* restore hardware defaults so runtime suspend can use it */
>> +	pci_read_config_word(rp, rp->pm_cap + PCI_PM_PMC, &pmc);
>> +	rp->pme_support = FIELD_GET(PCI_PM_CAP_PME_MASK, pmc);
>> +
>> +	return -EEXIST;
>> +}
>> +
>> +static void quirk_reenable_pme(struct pci_dev *dev)
>> +{
>> +	bool suspend = FALSE;
>> +
>> +	pci_walk_bus(dev->bus, modify_pme_amd_usb4, (void *)&suspend);
> 
> and here
> 
> 	pci_walk_bus(dev->bus, modify_pme_amd_usb4, (void *)false);
> 
>> +}
>> +
>> +static void quirk_disable_pme_suspend(struct pci_dev *dev)
>> +{
>> +	bool suspend = TRUE;
>> +
>> +	/* skip for runtime suspend */
>> +	if (pm_suspend_target_state == PM_SUSPEND_ON)
>> +		return;
>> +
>> +	pci_walk_bus(dev->bus, modify_pme_amd_usb4, (void *)&suspend);
> 
> here
> 
> 	pci_walk_bus(dev->bus, modify_pme_amd_usb4, (void *)true);
>> +}
>> +
>> +DECLARE_PCI_FIXUP_SUSPEND(PCI_VENDOR_ID_AMD, 0x14b9, quirk_disable_pme_suspend);
>> +DECLARE_PCI_FIXUP_RESUME(PCI_VENDOR_ID_AMD, 0x14b9, quirk_reenable_pme);
>> +DECLARE_PCI_FIXUP_SUSPEND(PCI_VENDOR_ID_AMD, 0x14eb, quirk_disable_pme_suspend);
>> +DECLARE_PCI_FIXUP_RESUME(PCI_VENDOR_ID_AMD, 0x14eb, quirk_reenable_pme);
>> +#endif /* CONFIG_SUSPEND */
>> -- 
>> 2.34.1