On Thu, 2025-08-14 at 15:25 -0500, Bjorn Helgaas wrote: > On Wed, Aug 13, 2025 at 10:45:23PM +0800, Hans Zhang wrote: > > Dear Maintainers, > > > > This patch series addresses long-standing code duplication in PCI > > capability discovery logic across the PCI core and controller drivers. > > The existing implementation ties capability search to fully initialized > > PCI device structures, limiting its usability during early controller > > initialization phases where device/bus structures may not yet be > > available. > > > > The primary goal is to decouple capability discovery from PCI device > > dependencies by introducing a unified framework using config space > > accessor-based macros. This enables: > > > > 1. Early Capability Discovery: Host controllers (e.g., Cadence, DWC) > > can now perform capability searches during pre-initialization stages > > using their native config accessors. > > > > 2. Code Consolidation: Common logic for standard and extended capability > > searches is refactored into shared macros (`PCI_FIND_NEXT_CAP` and > > `PCI_FIND_NEXT_EXT_CAP`), eliminating redundant implementations. > > > > 3. Safety and Maintainability: TTL checks are centralized within the > > macros to prevent infinite loops, while hardcoded offsets in drivers > > are replaced with dynamic discovery, reducing fragility. > > > > Key improvements include: > > - Driver Conversions: DesignWare and Cadence drivers are migrated to > > use the new macros, removing device-specific assumptions and ensuring > > consistent error handling. > > > > - Enhanced Readability: Magic numbers are replaced with symbolic > > constants, and config space accessors are standardized for clarity. > > > > - Backward Compatibility: Existing PCI core behavior remains unchanged. > > > > --- > > Dear Niklas and Gerd, > > > > Can you test this series of patches on the s390? > > > > Thank you very much. > > --- > > > > --- > > Changes since v14: > > - Delete the first patch in the v14 series. > > - The functions that can obtain the values of the registers u8/u16/u32 are > > directly called in PCI_FIND_NEXT_CAP() and PCI_FIND_NEXT_EXT_CAP(). > > Use the pci_bus_read_config_byte/word/dword function directly. > > - Delete dw_pcie_read_cfg and redefine three functions: dw_pcie_read_cfg_byte/word/dword. > > - Delete cdns_pcie_read_cfg and redefine three functions: cdns_pcie_read_cfg_byte/word/dword. > > > > Changes since v13: > > - Split patch 3/6 into two patches for searching standard and extended capability. (Bjorn) > > - Optimize the code based on the review comments from Bjorn. > > - Patch 5/7 and 6/7 use simplified macro definitions: PCI_FIND_NEXT_CAP(), PCI_FIND_NEXT_EXT_CAP(). > > - The other patches have not been modified. > > > > Changes since v12: > > - Modify some commit messages, code format issues, and optimize the function return values. > > > > Changes since v11: > > - Resolved some compilation warning. > > - Add some include. > > - Add the *** BLURB HERE *** description(Corrected by Mani and Krzysztof). > > > > Changes since v10: > > - The patch [v10 2/6] remove #include <uapi/linux/pci_regs.h> and add macro definition comments. > > - The patch [v10 3/6] remove #include <uapi/linux/pci_regs.h> and commit message were modified. > > - The other patches have not been modified. > > > > Changes since v9: > > - Resolved [v9 4/6] compilation error. > > The latest 6.15 rc1 merge __dw_pcie_find_vsec_capability, which uses > > dw_pcie_find_next_ext_capability. > > - The other patches have not been modified. > > > > Changes since v8: > > - Split patch. > > - The patch commit message were modified. > > - Other patches(4/6, 5/6, 6/6) are unchanged. > > > > Changes since v7: > > - Patch 2/5 and 3/5 compilation error resolved. > > - Other patches are unchanged. > > > > Changes since v6: > > - Refactor capability search into common macros. > > - Delete pci-host-helpers.c and MAINTAINERS. > > > > Changes since v5: > > - If you put the helpers in drivers/pci/pci.c, they unnecessarily enlarge > > the kernel's .text section even if it's known already at compile time > > that they're never going to be used (e.g. on x86). > > - Move the API for find capabilitys to a new file called > > pci-host-helpers.c. > > - Add new patch for MAINTAINERS. > > > > Changes since v4: > > - Resolved [v4 1/4] compilation warning. > > - The patch subject and commit message were modified. > > > > Changes since v3: > > - Resolved [v3 1/4] compilation error. > > - Other patches are not modified. > > > > Changes since v2: > > - Add and split into a series of patches. > > --- > > > > Hans Zhang (6): > > PCI: Clean up __pci_find_next_cap_ttl() readability > > PCI: Refactor capability search into PCI_FIND_NEXT_CAP() > > PCI: Refactor extended capability search into PCI_FIND_NEXT_EXT_CAP() > > PCI: dwc: Use PCI core APIs to find capabilities > > PCI: cadence: Use PCI core APIs to find capabilities > > PCI: cadence: Use cdns_pcie_find_*capability() to avoid hardcoding > > offsets > > > > .../pci/controller/cadence/pcie-cadence-ep.c | 38 +++++---- > > drivers/pci/controller/cadence/pcie-cadence.c | 14 +++ > > drivers/pci/controller/cadence/pcie-cadence.h | 39 +++++++-- > > drivers/pci/controller/dwc/pcie-designware.c | 77 ++--------------- > > drivers/pci/controller/dwc/pcie-designware.h | 21 +++++ > > drivers/pci/pci.c | 76 +++-------------- > > drivers/pci/pci.h | 85 +++++++++++++++++++ > > include/uapi/linux/pci_regs.h | 3 + > > 8 files changed, 194 insertions(+), 159 deletions(-) > > I applied this on pci/capability-search for v6.18, thanks! > > Niklas, I added your Tested-by, omitting the dwc and cadence patches > because I think you tested s390 and probably didn't exercise dwc or > cadence. Thanks very much to you and Gerd for finding the issue and > testing the resolution! > > Bjorn Thanks, yes leaving out dwc and cadence makes sense. Though I do often also test on my private x86 systems this one was s390 only. Since I have you here and as you applied this one now and Lukas PCI/ERR stuff yesterday, is it possible that my series titled "PCI/ERR: s390/pci: Use pci_uevent_ers() in PCI recovery" somehow fell through your mail filters maybe due to not having any "PCI:" in a subject? Thanks, Niklas
