On Thu, 01 Dec 2022 13:33:59 -0800 Dan Williams <[email protected]> wrote:
> From: Robert Richter <[email protected]> > > A port of a CXL host bridge links to the bridge's ACPI device > (&adev->dev) with its corresponding uport/dport device (uport_dev and > dport_dev respectively). The device is not a direct parent device in > the PCI topology as pdev->dev.parent points to a PCI bridge's (struct > pci_host_bridge) device. The following CXL memory device hierarchy > would be valid for an endpoint once an RCD EP would be enabled (note > this will be done in a later patch): > > VH mode: > > cxlmd->dev.parent->parent > ^^^\^^^^^^\ ^^^^^^\ > \ \ pci_dev (Type 1, Downstream Port) > \ pci_dev (Type 0, PCI Express Endpoint) > cxl mem device > > RCD mode: > > cxlmd->dev.parent->parent > ^^^\^^^^^^\ ^^^^^^\ > \ \ pci_host_bridge > \ pci_dev (Type 0, RCiEP) > cxl mem device > > In VH mode a downstream port is created by port enumeration and thus > always exists. > > Now, in RCD mode the host bridge also already exists but it references > to an ACPI device. A port lookup by the PCI device's parent device > will fail as a direct link to the registered port is missing. The ACPI > device of the bridge must be determined first. > > To prevent this, change port registration of a CXL host to use the > bridge device instead. Do this also for the VH case as port topology > will better reflect the PCI topology then. > > Signed-off-by: Robert Richter <[email protected]> > [djbw: rebase on brige mocking] > Reviewed-by: Robert Richter <[email protected]> > Signed-off-by: Dan Williams <[email protected]> Trivial comment inline. Looks fine to me otherwise... Reviewed-by: Jonathan Cameron <[email protected]> > --- > drivers/cxl/acpi.c | 35 +++++++++++++++++++---------------- > 1 file changed, 19 insertions(+), 16 deletions(-) > > diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c > index b8407b77aff6..50d82376097c 100644 > --- a/drivers/cxl/acpi.c > +++ b/drivers/cxl/acpi.c > @@ -193,35 +193,34 @@ static int add_host_bridge_uport(struct device *match, > void *arg) > { > struct cxl_port *root_port = arg; > struct device *host = root_port->dev.parent; > - struct acpi_device *bridge = to_cxl_host_bridge(host, match); > + struct acpi_device *hb = to_cxl_host_bridge(host, match); > struct acpi_pci_root *pci_root; > struct cxl_dport *dport; > struct cxl_port *port; > + struct device *bridge; > int rc; > > - if (!bridge) > + if (!hb) > return 0; > > - dport = cxl_find_dport_by_dev(root_port, match); > + pci_root = acpi_pci_find_root(hb->handle); > + bridge = pci_root->bus->bridge; > + dport = cxl_find_dport_by_dev(root_port, bridge); > if (!dport) { > dev_dbg(host, "host bridge expected and not found\n"); > return 0; > } > > - /* > - * Note that this lookup already succeeded in > - * to_cxl_host_bridge(), so no need to check for failure here > - */ > - pci_root = acpi_pci_find_root(bridge->handle); > - rc = devm_cxl_register_pci_bus(host, match, pci_root->bus); > + rc = devm_cxl_register_pci_bus(host, bridge, pci_root->bus); > if (rc) > return rc; > > - port = devm_cxl_add_port(host, match, dport->component_reg_phys, dport); > + port = devm_cxl_add_port(host, bridge, dport->component_reg_phys, > + dport); > if (IS_ERR(port)) > return PTR_ERR(port); > > - dev_info(pci_root->bus->bridge, "host supports CXL\n"); > + dev_info(bridge, "host supports CXL\n"); > > return 0; > } > @@ -253,18 +252,20 @@ static int cxl_get_chbcr(union acpi_subtable_headers > *header, void *arg, > static int add_host_bridge_dport(struct device *match, void *arg) > { > acpi_status status; > + struct device *bridge; > unsigned long long uid; > struct cxl_dport *dport; > struct cxl_chbs_context ctx; > + struct acpi_pci_root *pci_root; > struct cxl_port *root_port = arg; > struct device *host = root_port->dev.parent; > - struct acpi_device *bridge = to_cxl_host_bridge(host, match); > + struct acpi_device *hb = to_cxl_host_bridge(host, match); > > - if (!bridge) > + if (!hb) > return 0; > > - status = acpi_evaluate_integer(bridge->handle, METHOD_NAME__UID, NULL, > - &uid); > + status = > + acpi_evaluate_integer(hb->handle, METHOD_NAME__UID, NULL, &uid); Bit ugly. Maybe a good case for a slightly longer line! > if (status != AE_OK) { > dev_err(match, "unable to retrieve _UID\n"); > return -ENODEV; > @@ -285,7 +286,9 @@ static int add_host_bridge_dport(struct device *match, > void *arg) > > dev_dbg(match, "CHBCR found: 0x%08llx\n", (u64)ctx.chbcr); > > - dport = devm_cxl_add_dport(root_port, match, uid, ctx.chbcr); > + pci_root = acpi_pci_find_root(hb->handle); > + bridge = pci_root->bus->bridge; > + dport = devm_cxl_add_dport(root_port, bridge, uid, ctx.chbcr); > if (IS_ERR(dport)) > return PTR_ERR(dport); > >
