On 5/19/26 21:57, Manivannan Sadhasivam wrote:
On Sat, May 09, 2026 at 09:51:49PM +0800, Hans Zhang wrote:
The DWC PCIe core and its many platform drivers repeatedly call
dw_pcie_find_capability(pci, PCI_CAP_ID_EXP) to obtain the offset of the
PCI Express Capability structure. This is wasteful and makes the code
verbose. And some even search for the PCI_CAP_ID_EXP offset value within
the suspend/resume functions.
Sashiko has flagged some real issues with this series in accessing DBI space
very early and 'pci->pcie_cap' being 0.
Hi Mani,
We have discussed this issue in the Cadence driver. I think it won't
cause any problems. Specifically as follows:
https://lore.kernel.org/linux-pci/[email protected]/
"""
As per PCIe r7.0, sec 7.5.1.1.11, Since all PCI Express Functions are
required to implement the PCI Express Capability structure, which
must be included somewhere in this linked list.
"""
Bjorn also responded as follows:
https://lore.kernel.org/linux-pci/20260505212306.GA744158@bhelgaas/
"""
It's true that all Root Ports must have a PCIe Capability.
"""
Mani, should I continue to make the judgment that 'pci->pcie_cap' might
be 0 as per your instructions?
Best regards,
Hans
Those needs to be fixed.
- Mani
Add a cached pcie_cap field in struct dw_pcie and a helper
dw_pcie_get_pcie_cap() to initialize it once at probe time. Then replace
all explicit capability searches with the cached value across the
entire dwc subtree.
Hans Zhang (3):
PCI: dwc: Add pcie_cap field and helper in designware header
PCI: dwc: Use cached PCIe capability offset in core
PCI: dwc: Simplify platform drivers using cached capability offset
drivers/pci/controller/dwc/pci-imx6.c | 6 +--
.../pci/controller/dwc/pci-layerscape-ep.c | 4 +-
drivers/pci/controller/dwc/pci-meson.c | 4 +-
.../pci/controller/dwc/pcie-designware-ep.c | 4 +-
.../pci/controller/dwc/pcie-designware-host.c | 4 +-
drivers/pci/controller/dwc/pcie-designware.c | 16 +++---
drivers/pci/controller/dwc/pcie-designware.h | 17 +++++++
drivers/pci/controller/dwc/pcie-dw-rockchip.c | 15 +++---
drivers/pci/controller/dwc/pcie-eswin.c | 3 +-
drivers/pci/controller/dwc/pcie-fu740.c | 2 +-
drivers/pci/controller/dwc/pcie-intel-gw.c | 2 +-
drivers/pci/controller/dwc/pcie-qcom-ep.c | 11 ++--
drivers/pci/controller/dwc/pcie-qcom.c | 24 ++++-----
drivers/pci/controller/dwc/pcie-sophgo.c | 8 ++-
drivers/pci/controller/dwc/pcie-spacemit-k1.c | 5 +-
drivers/pci/controller/dwc/pcie-spear13xx.c | 6 +--
drivers/pci/controller/dwc/pcie-tegra194.c | 51 +++++++------------
17 files changed, 85 insertions(+), 97 deletions(-)
base-commit: 70390501d1944d4e5b8f7352be180fceb3a44132
--
2.34.1
