Messages in this thread | | | Date | Thu, 1 Sep 2022 09:50:33 +0200 | From | Robert Richter <> | Subject | Re: [PATCH 13/15] cxl/acpi: Rework devm_cxl_enumerate_ports() to support RCD mode |
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On 31.08.22 13:11:19, Jonathan Cameron wrote: > 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.)(
Yes, but software view is still the same, see other mail.
> > > 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);
Ok.
> > > + > > + /* > > + * 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.
Can improve this a little.
> > > > +} > > + > > 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.
I see your point here, will take a look.
Thanks,
-Robert
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