From ada02d0894fd0ae65bda4d5fbf88dad0a6cb0788 Mon Sep 17 00:00:00 2001 From: Manivannan Sadhasivam Date: Tue, 19 May 2026 13:41:20 +0530 Subject: PCI: Add pci_suspend_retains_context() to check if device state is preserved during suspend Currently, PCI endpoint drivers (e.g. nvme) use pm_suspend_via_firmware() to check whether device state is preserved during system suspend. If firmware will be invoked at the end of suspend, we don't know whether devices will retain their internal state. But device context might be lost due to platform issues as well. Having those checks in endpoint drivers will not scale and will cause a lot of code duplication. Add pci_suspend_retains_context() as a sole point of truth that the endpoint drivers can rely on to check whether they can expect the device context to be retained or not. If pci_suspend_retains_context() returns 'false', drivers need to prepare for context loss by performing actions such as resetting the device, saving the context, shutting it down etc. If it returns 'true', drivers do not need to perform any special action and can leave the device in active state. Right now, this API only incorporates pm_suspend_via_firmware(), but will be extended in future commits. Signed-off-by: Manivannan Sadhasivam Signed-off-by: Bjorn Helgaas Link: https://patch.msgid.link/20260519-l1ss-fix-v2-1-b2c3a4bdeb15@oss.qualcomm.com --- include/linux/pci.h | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'include/linux') diff --git a/include/linux/pci.h b/include/linux/pci.h index 2c4454583c11..f60f9e4e7b39 100644 --- a/include/linux/pci.h +++ b/include/linux/pci.h @@ -2086,6 +2086,8 @@ pci_release_mem_regions(struct pci_dev *pdev) pci_select_bars(pdev, IORESOURCE_MEM)); } +bool pci_suspend_retains_context(struct pci_dev *pdev); + #else /* CONFIG_PCI is not enabled */ static inline void pci_set_flags(int flags) { } @@ -2244,6 +2246,11 @@ pci_alloc_irq_vectors(struct pci_dev *dev, unsigned int min_vecs, static inline void pci_free_irq_vectors(struct pci_dev *dev) { } + +static inline bool pci_suspend_retains_context(struct pci_dev *pdev) +{ + return true; +} #endif /* CONFIG_PCI */ /* Include architecture-dependent settings and functions */ -- cgit v1.2.3 From b583b8fda6ddcf81fe1b02bec0d3c7fb43efc6de Mon Sep 17 00:00:00 2001 From: Manivannan Sadhasivam Date: Tue, 19 May 2026 13:41:21 +0530 Subject: PCI: Indicate context lost if L1SS exit is broken during resume from system suspend Per PCIe v7.0, sec 5.5.3.3.1, when exiting L1.2 due to an endpoint asserting CLKREQ# signal, the REFCLK must be turned on within the latency advertised in the LTR message. This requirement applies to L1.1 as well. On some platforms like Qcom, these requirements are satisfied during OS runtime, but not while resuming from the system suspend. This happens because the PCIe RC driver may remove all resource votes and turn off the PHY analog circuitry during suspend to maximize power savings while keeping the link in L1SS. Consequently, when the endpoint asserts CLKREQ# to wake up, the RC driver must restore the PHY and enable the REFCLK. When this recovery process exceeds the L1SS exit latency time (roughly L10_REFCLK_ON + T_COMMONMODE), the endpoint may treat it as a fatal condition and trigger Link Down (LDn). This results in a reset that destroys the internal device state. So to indicate this platform limitation to the client drivers, introduce a new flag 'pci_host_bridge::broken_l1ss_resume' and check it in pci_suspend_retains_context(). If the flag is set by the RC driver, the API will return 'false' indicating the client drivers that the device context may not be retained and the drivers must be prepared for context loss. Signed-off-by: Manivannan Sadhasivam Signed-off-by: Bjorn Helgaas Link: https://patch.msgid.link/20260519-l1ss-fix-v2-2-b2c3a4bdeb15@oss.qualcomm.com --- include/linux/pci.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/linux') diff --git a/include/linux/pci.h b/include/linux/pci.h index f60f9e4e7b39..4fee00ec59d7 100644 --- a/include/linux/pci.h +++ b/include/linux/pci.h @@ -660,6 +660,8 @@ struct pci_host_bridge { unsigned int preserve_config:1; /* Preserve FW resource setup */ unsigned int size_windows:1; /* Enable root bus sizing */ unsigned int msi_domain:1; /* Bridge wants MSI domain */ + unsigned int broken_l1ss_resume:1; /* Resuming from L1SS during + system suspend is broken */ /* Resource alignment requirements */ resource_size_t (*align_resource)(struct pci_dev *dev, -- cgit v1.2.3