[PATCH v4 07/14] cxl/region: Use region data to get the root decoder

Robert Richter
2025-11-03T18:49:21Z

To find a region's root decoder, the endpoint's HPA range is used to
search the matching decoder by its range. With address translation the
endpoint decoder's range is in a different address space and thus
cannot be used to determine the root decoder.

The region parameters are encapsulated within struc cxl_region_context
and may include the translated Host Physical Address (HPA) range. Use
this context to identify the root decoder rather than relying on the
endpoint.

Modify cxl_find_root_decoder() and add the region context as
parameter. Rename this function to get_cxl_root_decoder() as a
counterpart to put_cxl_root_decoder(). Simplify the implementation by
removing function cxl_port_find_switch_decode(). The function is
unnecessary because it is not referenced or utilized elsewhere in the
code.

Signed-off-by: Robert Richter <rrichter@amd.com>
---
drivers/cxl/core/region.c | 50 +++++++++++++++++----------------------
1 file changed, 22 insertions(+), 28 deletions(-)

diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index 2cfc29a2b588..2dd9e9be4889 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -3350,47 +3350,39 @@ static int devm_cxl_add_dax_region(struct cxl_region *cxlr)
return rc;
}

-static int match_decoder_by_range(struct device *dev, const void *data)
+static int match_root_decoder(struct device *dev, const void *data)
{
const struct range *r1, *r2 = data;
- struct cxl_decoder *cxld;
+ struct cxl_root_decoder *cxlrd;

- if (!is_switch_decoder(dev))
+ if (!is_root_decoder(dev))
return 0;

- cxld = to_cxl_decoder(dev);
- r1 = &cxld->hpa_range;
- return range_contains(r1, r2);
-}
+ cxlrd = to_cxl_root_decoder(dev);
+ r1 = &cxlrd->cxlsd.cxld.hpa_range;

-static struct cxl_decoder *
-cxl_port_find_switch_decoder(struct cxl_port *port, struct range *hpa_range)
-{
- struct device *cxld_dev = device_find_child(&port->dev, hpa_range,
- match_decoder_by_range);
-
- return cxld_dev ? to_cxl_decoder(cxld_dev) : NULL;
+ return range_contains(r1, r2);
}

static struct cxl_root_decoder *
-cxl_find_root_decoder(struct cxl_endpoint_decoder *cxled)
+get_cxl_root_decoder(struct cxl_endpoint_decoder *cxled,
+ struct cxl_region_context *ctx)
{
- 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 *root, *cxld = &cxled->cxld;
- struct range *hpa_range = &cxld->hpa_range;
+ struct device *cxlrd_dev;

- root = cxl_port_find_switch_decoder(&cxl_root->port, hpa_range);
- if (!root) {
- dev_err(cxlmd->dev.parent,
+ cxlrd_dev = device_find_child(&cxl_root->port.dev, &ctx->hpa_range,
+ match_root_decoder);
+ if (!cxlrd_dev) {
+ dev_err(port->uport_dev,
"%s:%s no CXL window for range %#llx:%#llx\n",
- dev_name(&cxlmd->dev), dev_name(&cxld->dev),
- hpa_range->start, hpa_range->end);
- return NULL;
+ dev_name(&ctx->cxlmd->dev), dev_name(&cxled->cxld.dev),
+ ctx->hpa_range.start, ctx->hpa_range.end);
+ return ERR_PTR(-ENXIO);
}

- return to_cxl_root_decoder(&root->dev);
+ return to_cxl_root_decoder(cxlrd_dev);
}

static int match_region_by_range(struct device *dev, const void *data)
@@ -3584,9 +3576,11 @@ int cxl_add_to_region(struct cxl_endpoint_decoder *cxled)
};

struct cxl_root_decoder *cxlrd __free(put_cxl_root_decoder) =
- cxl_find_root_decoder(cxled);
- if (!cxlrd)
- return -ENXIO;
+ get_cxl_root_decoder(cxled, &ctx);
+
+ rc = PTR_ERR_OR_ZERO(cxlrd);
+ if (rc)
+ return rc;

/*
* Ensure that if multiple threads race to construct_region()
--
2.47.3