On Thursday, September 6, 2018 5:50:20 PM CEST Mika Westerberg wrote:
> In order to have better power management for Thunderbolt PCIe chains,
> Windows enables power management for native PCIe hotplug ports if there
> is following ACPI _DSD attached to the root port:
>
> Name (_DSD, Package () {
> ToUUID ("6211e2c0-58a3-4af3-90e1-927a4e0c55a4"),
> Package () {
> Package () {"HotPlugSupportInD3", 1}
> }
> })
>
> This is also documented in:
>
> https://docs.microsoft.com/en-us/windows-hardware/drivers/pci/dsd-for-pcie-root-ports#identifying-pcie-root-ports-supporting-hot-plug-in-d3
>
> Do the same in Linux by introducing new firmware PM callback (->bridge_d3())
> and then implement it for ACPI based systems so that the above property is
> checked.
>
> There is one catch, though. The initial pci_dev->bridge_d3 is set before
> the root port has ACPI companion bound (the device is not added to the
> PCI bus either) so we need to look up the ACPI companion manually in
> that case in acpi_pci_bridge_d3().
>
> Signed-off-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
> ---
> drivers/acpi/property.c | 3 +++
> drivers/pci/pci-acpi.c | 41 +++++++++++++++++++++++++++++++++++++++++
> drivers/pci/pci.c | 9 +++++++++
> drivers/pci/pci.h | 3 +++
> 4 files changed, 56 insertions(+)
>
> diff --git a/drivers/acpi/property.c b/drivers/acpi/property.c
> index f3ddb279d2de..f9d63ee9f623 100644
> --- a/drivers/acpi/property.c
> +++ b/drivers/acpi/property.c
> @@ -28,6 +28,9 @@ static const guid_t prp_guids[] = {
> /* ACPI _DSD device properties GUID: daffd814-6eba-4d8c-8a91-bc9bbf4aa301 */
> GUID_INIT(0xdaffd814, 0x6eba, 0x4d8c,
> 0x8a, 0x91, 0xbc, 0x9b, 0xbf, 0x4a, 0xa3, 0x01),
> + /* Hotplug in D3 GUID: 6211e2c0-58a3-4af3-90e1-927a4e0c55a4 */
> + GUID_INIT(0x6211e2c0, 0x58a3, 0x4af3,
> + 0x90, 0xe1, 0x92, 0x7a, 0x4e, 0x0c, 0x55, 0xa4),
> };
>
> static const guid_t ads_guid =
> diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c
> index a4a8c02deaa0..c0394232fd93 100644
> --- a/drivers/pci/pci-acpi.c
> +++ b/drivers/pci/pci-acpi.c
> @@ -519,6 +519,46 @@ static pci_power_t acpi_pci_choose_state(struct pci_dev *pdev)
> return PCI_POWER_ERROR;
> }
>
> +static struct acpi_device *acpi_pci_find_companion(struct device *dev);
> +
> +static bool acpi_pci_bridge_d3(struct pci_dev *dev)
> +{
> + const struct fwnode_handle *fwnode;
> + struct acpi_device *adev;
> + struct pci_dev *root;
> + u8 val;
> +
> + if (!dev->is_hotplug_bridge)
> + return false;
> +
> + /*
> + * Look for a special _DSD property for the root port and if it
> + * is set we know the hierarchy behind it supports D3 just fine.
> + */
> + root = pci_find_pcie_root_port(dev);
> + if (!root)
> + return false;
> +
> + adev = ACPI_COMPANION(&root->dev);
> + if (root == dev) {
> + /*
> + * It is possible that the ACPI companion is not yet bound
> + * for the root port so look it up manually here.
> + */
> + if (!adev && !pci_dev_is_added(root))
> + adev = acpi_pci_find_companion(&root->dev);
> + }
> +
> + if (!adev)
> + return false;
> +
> + fwnode = acpi_fwnode_handle(adev);
> + if (fwnode_property_read_u8(fwnode, "HotPlugSupportInD3", &val))
> + return false;
> +
> + return val == 1;
> +}
> +
> static bool acpi_pci_power_manageable(struct pci_dev *dev)
> {
> struct acpi_device *adev = ACPI_COMPANION(&dev->dev);
> @@ -635,6 +675,7 @@ static bool acpi_pci_need_resume(struct pci_dev *dev)
> }
>
> static const struct pci_platform_pm_ops acpi_pci_platform_pm = {
> + .bridge_d3 = acpi_pci_bridge_d3,
> .is_manageable = acpi_pci_power_manageable,
> .set_state = acpi_pci_set_power_state,
> .get_state = acpi_pci_get_power_state,
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 074f3f0253f9..ce212eb10be9 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -791,6 +791,11 @@ static inline bool platform_pci_need_resume(struct pci_dev *dev)
> return pci_platform_pm ? pci_platform_pm->need_resume(dev) : false;
> }
>
> +static inline bool platform_pci_bridge_d3(struct pci_dev *dev)
> +{
> + return pci_platform_pm ? pci_platform_pm->bridge_d3(dev) : false;
> +}
> +
> /**
> * pci_raw_set_power_state - Use PCI PM registers to set the power state of
> * given PCI device
> @@ -2513,6 +2518,10 @@ bool pci_bridge_d3_possible(struct pci_dev *bridge)
> if (bridge->is_thunderbolt)
> return true;
>
> + /* Platform might know better if the bridge supports D3 */
> + if (platform_pci_bridge_d3(bridge))
> + return true;
> +
> /*
> * Hotplug ports handled natively by the OS were not validated
> * by vendors for runtime D3 at least until 2018 because there
> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
> index 6e0d1528d471..66fd5c1bf71b 100644
> --- a/drivers/pci/pci.h
> +++ b/drivers/pci/pci.h
> @@ -39,6 +39,8 @@ int pci_bridge_secondary_bus_reset(struct pci_dev *dev);
> /**
> * struct pci_platform_pm_ops - Firmware PM callbacks
> *
> + * @bridge_d3: Does the bridge allow entering into D3
> + *
> * @is_manageable: returns 'true' if given device is power manageable by the
> * platform firmware
> *
> @@ -60,6 +62,7 @@ int pci_bridge_secondary_bus_reset(struct pci_dev *dev);
> * these callbacks are mandatory.
> */
> struct pci_platform_pm_ops {
> + bool (*bridge_d3)(struct pci_dev *dev);
> bool (*is_manageable)(struct pci_dev *dev);
> int (*set_state)(struct pci_dev *dev, pci_power_t state);
> pci_power_t (*get_state)(struct pci_dev *dev);
>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
