On Thu, Nov 06, 2025 at 12:36:38PM -0600, Bjorn Helgaas wrote: > Cache the PCIe Link Capabilities register in struct pci_dev so quirks can > remove features to avoid hardware defects. The idea is: > > - set_pcie_port_type() reads PCIe Link Capabilities and caches it in > dev->lnkcap > > - HEADER quirks can update the cached dev->lnkcap to remove advertised > features that don't work correctly > > - pcie_aspm_cap_init() relies on dev->lnkcap and ignores any features not > advertised there
I realize that memory is cheap, but it still feels a bit wasteful to cache the entire 32-bit register wholesale. It contains reserved bits as of PCIe r7.0, various uninteresting bits and portions of it are already cached elsewhere and thus now duplicated. I'm wondering if it would make sense to instead only cache the ASPM bits that are relevant here? That's the approach we've followed so far. You're initializing the link_active_reporting bit from the newly cached lnkcap register, I'd prefer having a static inline instead which extracts the bit from the cached register on demand, thus obviating the need to have a duplicate cached copy of the bit. pci_set_bus_speed() caches bus->max_bus_speed from the Link Capabilities register and isn't converted by this patch to use the cached register. There are various others, e.g. get_port_device_capability() in drivers/pci/pcie/portdrv.c could also get PCI_EXP_LNKCAP_LBNC from the cached lnkcap register. Same for pcie_get_supported_speeds(). If the intention is to convert these in a separate step in v6.19, it would be good to mention that in the changelog. Thanks, Lukas
