[PATCH v3 09/18] cxl/region: Factor out code to find the root decoder

Robert Richter
2025-02-11T09:54:52Z

In function cxl_add_to_region() there is code to determine the root
decoder associated to an endpoint decoder. Factor out that code for
later reuse. This has the benefit of reducing cxl_add_to_region()'s
function complexity.

The reference of cxlrd_dev can be freed earlier. Since the root
decoder exists as long as the root port exists and the endpoint
already holds a reference to the root port, this additional reference
is not needed. Though it looks obvious to use __free() for the
reference of cxlrd_dev here too, this is done in a later rework. So
just move the code.

Signed-off-by: Robert Richter <rrichter@amd.com>
Reviewed-by: Gregory Price <gourry@gourry.net>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Tested-by: Gregory Price <gourry@gourry.net>
---
drivers/cxl/core/region.c | 55 ++++++++++++++++++++++++++-------------
1 file changed, 37 insertions(+), 18 deletions(-)

diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index 0e38bcb43be6..c641c8922455 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -3203,6 +3203,38 @@ static int match_root_decoder_by_range(struct device *dev,
return range_contains(r1, r2);
}

+static struct cxl_root_decoder *
+cxl_find_root_decoder(struct cxl_endpoint_decoder *cxled)
+{
+ struct cxl_memdev *cxlmd = cxled_to_memdev(cxled);
+ struct cxl_port *port = cxled_to_port(cxled);
+ struct cxl_root *cxl_root __free(put_cxl_root) = find_cxl_root(port);
+ struct cxl_decoder *cxld = &cxled->cxld;
+ struct range *hpa = &cxld->hpa_range;
+ struct device *cxlrd_dev;
+
+ cxlrd_dev = device_find_child(&cxl_root->port.dev, hpa,
+ match_root_decoder_by_range);
+ if (!cxlrd_dev) {
+ dev_err(cxlmd->dev.parent,
+ "%s:%s no CXL window for range %#llx:%#llx\n",
+ dev_name(&cxlmd->dev), dev_name(&cxld->dev),
+ cxld->hpa_range.start, cxld->hpa_range.end);
+ return NULL;
+ }
+
+ /*
+ * device_find_child() created a reference to the root
+ * decoder. Since the root decoder exists as long as the root
+ * port exists and the endpoint already holds a reference to
+ * the root port, this additional reference is not needed.
+ * Free it here.
+ */
+ put_device(cxlrd_dev);
+
+ return to_cxl_root_decoder(cxlrd_dev);
+}
+
static int match_region_by_range(struct device *dev, const void *data)
{
struct cxl_region_params *p;
@@ -3314,29 +3346,17 @@ static struct cxl_region *construct_region(struct cxl_root_decoder *cxlrd,

int cxl_add_to_region(struct cxl_endpoint_decoder *cxled)
{
- struct cxl_memdev *cxlmd = cxled_to_memdev(cxled);
- struct cxl_port *port = cxled_to_port(cxled);
- struct cxl_root *cxl_root __free(put_cxl_root) = find_cxl_root(port);
struct range *hpa = &cxled->cxld.hpa_range;
- struct cxl_decoder *cxld = &cxled->cxld;
- struct device *cxlrd_dev, *region_dev;
+ struct device *region_dev;
struct cxl_root_decoder *cxlrd;
struct cxl_region_params *p;
struct cxl_region *cxlr;
bool attach = false;
int rc;

- cxlrd_dev = device_find_child(&cxl_root->port.dev, &cxld->hpa_range,
- match_root_decoder_by_range);
- if (!cxlrd_dev) {
- dev_err(cxlmd->dev.parent,
- "%s:%s no CXL window for range %#llx:%#llx\n",
- dev_name(&cxlmd->dev), dev_name(&cxld->dev),
- cxld->hpa_range.start, cxld->hpa_range.end);
+ cxlrd = cxl_find_root_decoder(cxled);
+ if (!cxlrd)
return -ENXIO;
- }
-
- cxlrd = to_cxl_root_decoder(cxlrd_dev);

/*
* Ensure that if multiple threads race to construct_region() for @hpa
@@ -3354,7 +3374,7 @@ int cxl_add_to_region(struct cxl_endpoint_decoder *cxled)

rc = PTR_ERR_OR_ZERO(cxlr);
if (rc)
- goto out;
+ return rc;

attach_target(cxlr, cxled, -1, TASK_UNINTERRUPTIBLE);

@@ -3375,8 +3395,7 @@ int cxl_add_to_region(struct cxl_endpoint_decoder *cxled)
}

put_device(region_dev);
-out:
- put_device(cxlrd_dev);
+
return rc;
}
EXPORT_SYMBOL_NS_GPL(cxl_add_to_region, "CXL");
--
2.39.5