Messages in this thread | | | Date | Wed, 31 Aug 2022 13:11:19 +0100 | From | Jonathan Cameron <> | Subject | Re: [PATCH 13/15] cxl/acpi: Rework devm_cxl_enumerate_ports() to support RCD mode |
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On Wed, 31 Aug 2022 10:16:01 +0200 Robert Richter <rrichter@amd.com> wrote:
> RCD mode has a different enumeration scheme other than in CXL VH mode. > An RCD is directly connected to an RCH without downstream and upstream > ports showing up in between in the PCI hierarchy. Due to the direct > connection of RCD and RCH, the host bridge is always the RCD's parent > instead of the grandparent. Mentioned earlier, but that's not quite true. There is a reference in the spec to allowing it to be under a root port (some sort of virtual structure - I'm not sure of 'why' you would that though.)(
> Modify devm_cxl_enumerate_ports() > respectively.
Don't line wrap above.
> > Implement this by introducing a function to determine the device's > downstream port. The 'for' loop is adjusted for RCD mode and in this > case find_cxl_port() will always find the host's associated port and > the loop iteration stops. > > Signed-off-by: Robert Richter <rrichter@amd.com> > --- > drivers/cxl/core/port.c | 36 ++++++++++++++++++++++++------------ > 1 file changed, 24 insertions(+), 12 deletions(-) > > diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c > index 61e9915162d5..08b99423dbf8 100644 > --- a/drivers/cxl/core/port.c > +++ b/drivers/cxl/core/port.c > @@ -1084,6 +1084,22 @@ static struct device *grandparent(struct device *dev) > return NULL; > } > > +static struct device *cxl_mem_dport_dev(struct cxl_memdev *cxlmd) > +{ > + struct device *dev = cxlmd->dev.parent; > + struct pci_dev *pdev = to_pci_dev(cxlmd->dev.parent);
to_pci_dev(dev);
> + > + /* > + * An RCiEP is directly connected to the root bridge without > + * any PCI bridges/ports in between. Reduce the parent level > + * for those. > + */ > + if (pci_pcie_type(pdev) == PCI_EXP_TYPE_RC_END) > + return dev; > + > + return dev->parent; Switching from grandparent to this is a little confusing because it's done in two steps. Perhaps use return grandparent(cmlmd->dev); here to keep that connection and rename dev in this function to parent.
Far too many devices in here with similar names for it to be easy to read.
> +} > + > static void delete_endpoint(void *data) > { > struct cxl_memdev *cxlmd = data; > @@ -1339,7 +1355,7 @@ static int add_port_attach_ep(struct cxl_memdev *cxlmd, > int devm_cxl_enumerate_ports(struct cxl_memdev *cxlmd) > { > struct device *dev = &cxlmd->dev; > - struct device *iter; > + struct device *dport_dev; > int rc; > > rc = devm_add_action_or_reset(&cxlmd->dev, cxl_detach_ep, cxlmd); > @@ -1352,25 +1368,21 @@ int devm_cxl_enumerate_ports(struct cxl_memdev *cxlmd) > * attempt fails. > */ > retry: > - for (iter = dev; iter; iter = grandparent(iter)) { > - struct device *dport_dev = grandparent(iter); > + for (dport_dev = cxl_mem_dport_dev(cxlmd); dport_dev; > + dport_dev = grandparent(dport_dev)) {
I don't like looping for the RCD case as it relies a bit too much on subtle relationships between devices and parent.
Perhaps better to factor out the contents of the loop, then handle the RCD case separately from the main loop. I haven't tried it, so perhaps that looks even less readable.
> struct device *uport_dev; > struct cxl_dport *dport; > struct cxl_port *port; > > - if (!dport_dev) > - return 0; > - > uport_dev = dport_dev->parent; > if (!uport_dev) { > - dev_warn(dev, "at %s no parent for dport: %s\n", > - dev_name(iter), dev_name(dport_dev)); > + dev_warn(dev, "no parent for dport: %s\n", > + dev_name(dport_dev)); > return -ENXIO; > } > > - dev_dbg(dev, "scan: iter: %s dport_dev: %s parent: %s\n", > - dev_name(iter), dev_name(dport_dev), > - dev_name(uport_dev)); > + dev_dbg(dev, "scan: dport_dev: %s parent: %s\n", > + dev_name(dport_dev), dev_name(uport_dev)); > port = find_cxl_port(dport_dev, &dport); > if (port) { > dev_dbg(&cxlmd->dev, > @@ -1418,7 +1430,7 @@ EXPORT_SYMBOL_NS_GPL(devm_cxl_enumerate_ports, CXL); > struct cxl_port *cxl_mem_find_port(struct cxl_memdev *cxlmd, > struct cxl_dport **dport) > { > - return find_cxl_port(grandparent(&cxlmd->dev), dport); > + return find_cxl_port(cxl_mem_dport_dev(cxlmd), dport); > } > EXPORT_SYMBOL_NS_GPL(cxl_mem_find_port, CXL); >
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