On Wed, 26 Jan 2022 15:59:07 -0800
Dan Williams <dan.j.williams@xxxxxxxxx> wrote:
> In preparation for switch port enumeration while also preserving the
> potential for multi-domain / multi-root CXL topologies. Introduce a
> 'struct device' generic mechanism for retrieving a root CXL port, if one
> is registered. Note that the only know multi-domain CXL configurations
> are running the cxl_test unit test on a system that also publishes an
> ACPI0017 device.
>
> With this in hand the nvdimm-bridge lookup can be with
> device_find_child() instead of bus_find_device() + custom mocked lookup
> infrastructure in cxl_test.
>
> The mechanism looks for a 2nd level port since the root level topology
> is platform-firmware specific and the 2nd level down follows standard
> PCIe topology expectations. The cxl_acpi 2nd level is associated with a
> PCIe Root Port.
>
> Reported-by: Ben Widawsky <ben.widawsky@xxxxxxxxx>
> Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
A question inline.
Thanks,
Jonathan
> ---
> Changes since v4:
> - reset @iter each loop otherwise only the first dport can be scanned.
>
> drivers/cxl/core/pmem.c | 14 ++++++++---
> drivers/cxl/core/port.c | 50 +++++++++++++++++++++++++++++++++++++++++
> drivers/cxl/cxl.h | 1 +
> tools/testing/cxl/Kbuild | 2 --
> tools/testing/cxl/mock_pmem.c | 24 --------------------
> 5 files changed, 61 insertions(+), 30 deletions(-)
> delete mode 100644 tools/testing/cxl/mock_pmem.c
>
> diff --git a/drivers/cxl/core/pmem.c b/drivers/cxl/core/pmem.c
> index 40b3f5030496..8de240c4d96b 100644
> --- a/drivers/cxl/core/pmem.c
> +++ b/drivers/cxl/core/pmem.c
> @@ -57,24 +57,30 @@ bool is_cxl_nvdimm_bridge(struct device *dev)
> }
> EXPORT_SYMBOL_NS_GPL(is_cxl_nvdimm_bridge, CXL);
>
> -__mock int match_nvdimm_bridge(struct device *dev, const void *data)
> +static int match_nvdimm_bridge(struct device *dev, void *data)
> {
> return is_cxl_nvdimm_bridge(dev);
> }
>
> struct cxl_nvdimm_bridge *cxl_find_nvdimm_bridge(struct cxl_nvdimm *cxl_nvd)
> {
> + struct cxl_port *port = find_cxl_root(&cxl_nvd->dev);
> struct device *dev;
>
> - dev = bus_find_device(&cxl_bus_type, NULL, cxl_nvd, match_nvdimm_bridge);
> + if (!port)
> + return NULL;
> +
> + dev = device_find_child(&port->dev, NULL, match_nvdimm_bridge);
> + put_device(&port->dev);
> +
> if (!dev)
> return NULL;
> +
> return to_cxl_nvdimm_bridge(dev);
> }
> EXPORT_SYMBOL_NS_GPL(cxl_find_nvdimm_bridge, CXL);
>
> -static struct cxl_nvdimm_bridge *
> -cxl_nvdimm_bridge_alloc(struct cxl_port *port)
> +static struct cxl_nvdimm_bridge *cxl_nvdimm_bridge_alloc(struct cxl_port *port)
> {
> struct cxl_nvdimm_bridge *cxl_nvb;
> struct device *dev;
> diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
> index 4c921c49f967..6447f12ef71d 100644
> --- a/drivers/cxl/core/port.c
> +++ b/drivers/cxl/core/port.c
> @@ -457,6 +457,56 @@ int devm_cxl_register_pci_bus(struct device *host, struct device *uport,
> }
> EXPORT_SYMBOL_NS_GPL(devm_cxl_register_pci_bus, CXL);
>
> +/* Find a 2nd level CXL port that has a dport that is an ancestor of @match */
> +static int match_cxl_root_child(struct device *dev, const void *match)
> +{
> + const struct device *iter = NULL;
> + struct cxl_port *port, *parent;
> + struct cxl_dport *dport;
> +
> + if (!is_cxl_port(dev))
> + return 0;
> +
> + port = to_cxl_port(dev);
> + if (is_cxl_root(port))
> + return 0;
> +
> + parent = to_cxl_port(port->dev.parent);
> + if (!is_cxl_root(parent))
> + return 0;
> +
> + cxl_device_lock(&port->dev);
> + list_for_each_entry(dport, &port->dports, list) {
> + iter = match;
This confuses me. In the call below to bus_find_device()
data == NULL, which ends up as match here.
So how does that ever find a match?
> + while (iter) {
> + if (iter == dport->dport)
> + goto out;
> + iter = iter->parent;
> + }
> + }
> +out:
> + cxl_device_unlock(&port->dev);
> +
> + return !!iter;
return iter; should be sufficient as docs just say non zero for a match
in bus_find_device() match functions.
> +}
> +
> +struct cxl_port *find_cxl_root(struct device *dev)
> +{
> + struct device *port_dev;
> + struct cxl_port *root;
> +
> + port_dev =
> + bus_find_device(&cxl_bus_type, NULL, dev, match_cxl_root_child);
Line breaking is rather ugly to my eye. Perhaps break
parameter list up instead?
> + if (!port_dev)
> + return NULL;
> +
> + root = to_cxl_port(port_dev->parent);
> + get_device(&root->dev);
> + put_device(port_dev);
> + return root;
> +}
> +EXPORT_SYMBOL_NS_GPL(find_cxl_root, CXL);
> +
> static struct cxl_dport *find_dport(struct cxl_port *port, int id)
> {
> struct cxl_dport *dport;
> diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
> index 4e8d504546c5..7523e4d60953 100644
> --- a/drivers/cxl/cxl.h
> +++ b/drivers/cxl/cxl.h
> @@ -298,6 +298,7 @@ struct cxl_port *devm_cxl_add_port(struct device *host, struct device *uport,
>
> int cxl_add_dport(struct cxl_port *port, struct device *dport, int port_id,
> resource_size_t component_reg_phys);
> +struct cxl_port *find_cxl_root(struct device *dev);
>
> struct cxl_decoder *to_cxl_decoder(struct device *dev);
> bool is_root_decoder(struct device *dev);
