Synthetic PCIe hierarchies, such as those created by Intel VMD, are not enumerated by firmware and do not receive BIOS-provided ASPM or CLKPM defaults. Devices in such domains may therefore run without the intended power management. Add a host-bridge mechanism that lets controller drivers supply their own defaults. A new aspm_default_link_state field in struct pci_host_bridge is set via pci_host_set_default_pcie_link_state(). During link initialization, if this field is non-zero, ASPM and CLKPM defaults come from it instead of BIOS. This enables drivers like VMD to align link power management with platform expectations and avoids embedding controller-specific quirks in ASPM core logic. Link: https://patchwork.ozlabs.org/project/linux-pci/patch/20250720190140.2639200-1-david.e.box%40linux.intel.com/ Signed-off-by: David E. Box <david.e.box@xxxxxxxxxxxxxxx> Tested-by: Manivannan Sadhasivam <mani@xxxxxxxxxx> Reviewed-by: Rafael J. Wysocki (Intel) <rafael@xxxxxxxxxx> --- Changes in V3: -- Changed pci_host_get_default_pcie_link_state() argument name from parent to dev. -- Applied changelog tags Changes in V2: -- Host field name changed to aspm_default_link_state. -- Added get/set functions for aspm_default_link_state. Only the setter is exported. Added a kernel-doc describing usage and particulars around meaning of 0. Changes in V1 from RFC: -- Rename field to aspm_dflt_link_state since it stores PCIE_LINK_STATE_XXX flags, not a policy enum. -- Move the field to struct pci_host_bridge since it's being applied to the entire host bridge per Mani's suggestion. -- During testing noticed that clkpm remained disabled and this was also handled by the formerly used pci_enable_link_state(). Add a check in pcie_clkpm_cap_init() as well to enable clkpm during init. drivers/pci/pcie/aspm.c | 42 +++++++++++++++++++++++++++++++++++++++-- include/linux/pci.h | 9 +++++++++ 2 files changed, 49 insertions(+), 2 deletions(-) diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c index 919a05b97647..851ca3d68e55 100644 --- a/drivers/pci/pcie/aspm.c +++ b/drivers/pci/pcie/aspm.c @@ -373,6 +373,39 @@ static void pcie_set_clkpm(struct pcie_link_state *link, int enable) pcie_set_clkpm_nocheck(link, enable); } +/** + * pci_host_set_default_pcie_link_state - set controller-provided default ASPM/CLKPM mask + * @host: host bridge on which to apply the defaults + * @state: PCIE_LINK_STATE_XXX flags + * + * Allows a PCIe controller driver to specify the default ASPM and/or + * Clock Power Management (CLKPM) link state mask that will be used + * for links under this host bridge during ASPM/CLKPM capability init. + * + * The value is consumed in pcie_aspm_cap_init() and pcie_clkpm_cap_init() + * to override the firmware-discovered defaults. + * + * Interpretation of aspm_default_link_state: + * - Nonzero: bitmask of PCIE_LINK_STATE_* values to be used as defaults + * - Zero: no override provided; ASPM/CLKPM defaults fall back to + * values discovered in hardware/firmware + * + * Note: zero is always treated as "unset", not as "force ASPM/CLKPM off". + */ +void pci_host_set_default_pcie_link_state(struct pci_host_bridge *host, + unsigned int state) +{ + host->aspm_default_link_state = state; +} +EXPORT_SYMBOL_GPL(pci_host_set_default_pcie_link_state); + +static u32 pci_host_get_default_pcie_link_state(struct pci_dev *dev) +{ + struct pci_host_bridge *host = pci_find_host_bridge(dev->bus); + + return host ? host->aspm_default_link_state : 0; +} + static void pcie_clkpm_cap_init(struct pcie_link_state *link, int blacklist) { int capable = 1, enabled = 1; @@ -394,7 +427,10 @@ static void pcie_clkpm_cap_init(struct pcie_link_state *link, int blacklist) enabled = 0; } link->clkpm_enabled = enabled; - link->clkpm_default = enabled; + if (pci_host_get_default_pcie_link_state(link->pdev) & PCIE_LINK_STATE_CLKPM) + link->clkpm_default = 1; + else + link->clkpm_default = enabled; link->clkpm_capable = capable; link->clkpm_disable = blacklist ? 1 : 0; } @@ -866,7 +902,9 @@ static void pcie_aspm_cap_init(struct pcie_link_state *link, int blacklist) } /* Save default state */ - link->aspm_default = link->aspm_enabled; + link->aspm_default = pci_host_get_default_pcie_link_state(parent); + if (!link->aspm_default) + link->aspm_default = link->aspm_enabled; /* Setup initial capable state. Will be updated later */ link->aspm_capable = link->aspm_support; diff --git a/include/linux/pci.h b/include/linux/pci.h index 59876de13860..8947cbaf9fa6 100644 --- a/include/linux/pci.h +++ b/include/linux/pci.h @@ -620,6 +620,10 @@ struct pci_host_bridge { unsigned int size_windows:1; /* Enable root bus sizing */ unsigned int msi_domain:1; /* Bridge wants MSI domain */ +#ifdef CONFIG_PCIEASPM + unsigned int aspm_default_link_state; /* Controller-provided default */ +#endif + /* Resource alignment requirements */ resource_size_t (*align_resource)(struct pci_dev *dev, const struct resource *res, @@ -1849,6 +1853,8 @@ int pci_disable_link_state(struct pci_dev *pdev, int state); int pci_disable_link_state_locked(struct pci_dev *pdev, int state); int pci_enable_link_state(struct pci_dev *pdev, int state); int pci_enable_link_state_locked(struct pci_dev *pdev, int state); +void pci_host_set_default_pcie_link_state(struct pci_host_bridge *host, + unsigned int state); void pcie_no_aspm(void); bool pcie_aspm_support_enabled(void); bool pcie_aspm_enabled(struct pci_dev *pdev); @@ -1861,6 +1867,9 @@ static inline int pci_enable_link_state(struct pci_dev *pdev, int state) { return 0; } static inline int pci_enable_link_state_locked(struct pci_dev *pdev, int state) { return 0; } +static inline void +pci_host_set_default_pcie_link_state(struct pci_host_bridge *host, + unsigned int state) { } static inline void pcie_no_aspm(void) { } static inline bool pcie_aspm_support_enabled(void) { return false; } static inline bool pcie_aspm_enabled(struct pci_dev *pdev) { return false; } base-commit: c17b750b3ad9f45f2b6f7e6f7f4679844244f0b9 -- 2.43.0
