Commit d35b495d authored by Dan Williams's avatar Dan Williams
Browse files

cxl/port: Fix find_cxl_root() for RCDs and simplify it 



The find_cxl_root() helper is used to lookup root decoders and other CXL
platform topology information for a given endpoint. It turns out that
for RCDs it has never worked. The result of find_cxl_root(&cxlmd->dev)
is always NULL for the RCH topology case because it expects to find a
cxl_port at the host-bridge. RCH topologies only have the root cxl_port
object with the host-bridge as a dport. While there are no reports of
this being a problem to date, by inspection region enumeration should
crash as a result of this problem, and it does in a local unit test for
this scenario.

However, an observation that ever since:

commit f17b558d ("cxl/pmem: Refactor nvdimm device registration, delete the workqueue")

...all callers of find_cxl_root() occur after the memdev connection to
the port topology has been established. That means that find_cxl_root()
can be simplified to a walk of the endpoint port topology to the root.
Switch to that arrangement which also fixes the RCD bug.

Fixes: a32320b7 ("cxl/region: Add region autodiscovery")
Reviewed-by: default avatarJonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: default avatarDave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/168002857715.50647.344876437247313909.stgit@dwillia2-xfh.jf.intel.com


Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
parent b70c2cf9

drivers/cxl/core/pmem.c

+3 −3
Original line number Diff line number Diff line
@@ -62,9 +62,9 @@ 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 device *start)

struct cxl_nvdimm_bridge *cxl_find_nvdimm_bridge(struct cxl_memdev *cxlmd)

{

	struct cxl_port *port = find_cxl_root(start);

	struct cxl_port *port = find_cxl_root(dev_get_drvdata(&cxlmd->dev));

	struct device *dev;



	if (!port)
@@ -253,7 +253,7 @@ int devm_cxl_add_nvdimm(struct cxl_memdev *cxlmd) 
	struct device *dev;

	int rc;



	cxl_nvb = cxl_find_nvdimm_bridge(&cxlmd->dev);

	cxl_nvb = cxl_find_nvdimm_bridge(cxlmd);

	if (!cxl_nvb)

		return -ENODEV;

drivers/cxl/core/port.c

+7 −31
Original line number Diff line number Diff line
@@ -823,41 +823,17 @@ static bool dev_is_cxl_root_child(struct device *dev) 
	return false;

}



/* Find a 2nd level CXL port that has a dport that is an ancestor of @match */

static int match_root_child(struct device *dev, const void *match)

struct cxl_port *find_cxl_root(struct cxl_port *port)

{

	const struct device *iter = NULL;

	struct cxl_dport *dport;

	struct cxl_port *port;



	if (!dev_is_cxl_root_child(dev))

		return 0;

	struct cxl_port *iter = port;



	port = to_cxl_port(dev);

	iter = match;

	while (iter) {

		dport = cxl_find_dport_by_dev(port, iter);

		if (dport)

			break;

		iter = iter->parent;

	}



	return !!iter;

}



struct cxl_port *find_cxl_root(struct device *dev)

{

	struct device *port_dev;

	struct cxl_port *root;

	while (iter && !is_cxl_root(iter))

		iter = to_cxl_port(iter->dev.parent);



	port_dev = bus_find_device(&cxl_bus_type, NULL, dev, match_root_child);

	if (!port_dev)

	if (!iter)

		return NULL;



	root = to_cxl_port(port_dev->parent);

	get_device(&root->dev);

	put_device(port_dev);

	return root;

	get_device(&iter->dev);

	return iter;

}

EXPORT_SYMBOL_NS_GPL(find_cxl_root, CXL);

drivers/cxl/core/region.c

+1 −1
Original line number Diff line number Diff line
@@ -2251,7 +2251,7 @@ static struct cxl_pmem_region *cxl_pmem_region_alloc(struct cxl_region *cxlr) 
		 * bridge for one device is the same for all.

		 */

		if (i == 0) {

			cxl_nvb = cxl_find_nvdimm_bridge(&cxlmd->dev);

			cxl_nvb = cxl_find_nvdimm_bridge(cxlmd);

			if (!cxl_nvb) {

				cxlr_pmem = ERR_PTR(-ENODEV);

				goto out;

drivers/cxl/cxl.h

+2 −2
Original line number Diff line number Diff line
@@ -658,7 +658,7 @@ struct pci_bus *cxl_port_to_pci_bus(struct cxl_port *port); 
struct cxl_port *devm_cxl_add_port(struct device *host, struct device *uport,

				   resource_size_t component_reg_phys,

				   struct cxl_dport *parent_dport);

struct cxl_port *find_cxl_root(struct device *dev);

struct cxl_port *find_cxl_root(struct cxl_port *port);

int devm_cxl_enumerate_ports(struct cxl_memdev *cxlmd);

void cxl_bus_rescan(void);

void cxl_bus_drain(void);
@@ -760,7 +760,7 @@ struct cxl_nvdimm *to_cxl_nvdimm(struct device *dev); 
bool is_cxl_nvdimm(struct device *dev);

bool is_cxl_nvdimm_bridge(struct device *dev);

int devm_cxl_add_nvdimm(struct cxl_memdev *cxlmd);

struct cxl_nvdimm_bridge *cxl_find_nvdimm_bridge(struct device *dev);

struct cxl_nvdimm_bridge *cxl_find_nvdimm_bridge(struct cxl_memdev *cxlmd);



#ifdef CONFIG_CXL_REGION

bool is_cxl_pmem_region(struct device *dev);

drivers/cxl/port.c

+1 −1
Original line number Diff line number Diff line
@@ -119,7 +119,7 @@ static int cxl_endpoint_port_probe(struct cxl_port *port) 
	 * This can't fail in practice as CXL root exit unregisters all

	 * descendant ports and that in turn synchronizes with cxl_port_probe()

	 */

	root = find_cxl_root(&cxlmd->dev);

	root = find_cxl_root(port);



	/*

	 * Now that all endpoint decoders are successfully enumerated, try to