| Message ID | 20220831081603.3415-16-rrichter@amd.com |
|---|---|
| State | Superseded |
| Delegated to: | Dan Williams |
| Headers | show |
| Series | cxl: Add support for Restricted CXL hosts (RCD mode) | expand |
Robert Richter wrote: > In RCD mode the CXL mem dev may be detected on the PCI bus before a > CXL host is brought up. This may cause a CXL mem initialization > failure as it expects the CXL host already detected. This is not unique to RCD mode. It is mitigated by the cxl_bus_rescan() at the completion of cxl_acpi_probe(). > Address this by > specifying the module dependencies using MODULE_SOFTDEP(). > > The following additional dependencies exist: > > * cxl_mem depends on cxl_acpi: The CXL hosts must be discovered > before the CXL device is initialized. > > * cxl_acpi depends on cxl_port: The acpi driver adds ports to the cxl > bus, the port driver should be loaded before. This might also work > if modules are loaded in different order, but a) it aligns with the > existing cxl_mem/cxl_port softdep and b) it always guarantees a fix > module load order. Why does a fixed module load order matter? > > Signed-off-by: Robert Richter <rrichter@amd.com> > --- > drivers/cxl/acpi.c | 1 + > drivers/cxl/mem.c | 1 + > 2 files changed, 2 insertions(+) > > diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c > index 56b2d222afcc..63a1cb295c07 100644 > --- a/drivers/cxl/acpi.c > +++ b/drivers/cxl/acpi.c > @@ -834,3 +834,4 @@ module_exit(cxl_host_exit); > MODULE_LICENSE("GPL v2"); > MODULE_IMPORT_NS(CXL); > MODULE_IMPORT_NS(ACPI); > +MODULE_SOFTDEP("pre: cxl_port"); The only reason cxl_acpi would need to preload cxl_port is if it wanted to do something like: port = devm_cxl_add_port(...); if (port->dev.driver) /* do something with an enabled port */ else /* do something else if the port failed to enable */ > diff --git a/drivers/cxl/mem.c b/drivers/cxl/mem.c > index 64ccf053d32c..ae13ec7d9894 100644 > --- a/drivers/cxl/mem.c > +++ b/drivers/cxl/mem.c > @@ -128,3 +128,4 @@ MODULE_ALIAS_CXL(CXL_DEVICE_MEMORY_EXPANDER); > * endpoint registration. > */ > MODULE_SOFTDEP("pre: cxl_port"); > +MODULE_SOFTDEP("pre: cxl_acpi"); There is no strict requirement that CXL topologies be limited to ACPI platforms. Per above, the cxl_mem driver will attach when the CXL root device finally appears, and async out-of-order arrival is ok.
diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c index 56b2d222afcc..63a1cb295c07 100644 --- a/drivers/cxl/acpi.c +++ b/drivers/cxl/acpi.c @@ -834,3 +834,4 @@ module_exit(cxl_host_exit); MODULE_LICENSE("GPL v2"); MODULE_IMPORT_NS(CXL); MODULE_IMPORT_NS(ACPI); +MODULE_SOFTDEP("pre: cxl_port"); diff --git a/drivers/cxl/mem.c b/drivers/cxl/mem.c index 64ccf053d32c..ae13ec7d9894 100644 --- a/drivers/cxl/mem.c +++ b/drivers/cxl/mem.c @@ -128,3 +128,4 @@ MODULE_ALIAS_CXL(CXL_DEVICE_MEMORY_EXPANDER); * endpoint registration. */ MODULE_SOFTDEP("pre: cxl_port"); +MODULE_SOFTDEP("pre: cxl_acpi");
In RCD mode the CXL mem dev may be detected on the PCI bus before a CXL host is brought up. This may cause a CXL mem initialization failure as it expects the CXL host already detected. Address this by specifying the module dependencies using MODULE_SOFTDEP(). The following additional dependencies exist: * cxl_mem depends on cxl_acpi: The CXL hosts must be discovered before the CXL device is initialized. * cxl_acpi depends on cxl_port: The acpi driver adds ports to the cxl bus, the port driver should be loaded before. This might also work if modules are loaded in different order, but a) it aligns with the existing cxl_mem/cxl_port softdep and b) it always guarantees a fix module load order. Signed-off-by: Robert Richter <rrichter@amd.com> --- drivers/cxl/acpi.c | 1 + drivers/cxl/mem.c | 1 + 2 files changed, 2 insertions(+)