cxl/region: Use region data to get the root decoder

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 struct 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.

Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Reviewed-by: Alison Schofield <alison.schofield@intel.com>
Tested-by: Gregory Price <gourry@gourry.net>
Signed-off-by: Robert Richter <rrichter@amd.com>
Link: https://patch.msgid.link/20260114164837.1076338-8-rrichter@amd.com
Signed-off-by: Dave Jiang <dave.jiang@intel.com>

diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index 60d2d1dae2aa32c59951e8c204e92ec3921f05ad..912796fd708e76e4c941df79ee12d2aac21e0036 100644 (file)
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -3469,47 +3469,44 @@ err:
        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);
-}
-
-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);
+       cxlrd = to_cxl_root_decoder(dev);
+       r1 = &cxlrd->cxlsd.cxld.hpa_range;
 
-       return cxld_dev ? to_cxl_decoder(cxld_dev) : NULL;
+       return range_contains(r1, r2);
 }
 
+/*
+ * Note, when finished with the device, drop the reference with
+ * put_device() or use the put_cxl_root_decoder helper.
+ */
 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) {
+       cxlrd_dev = device_find_child(&cxl_root->port.dev, &ctx->hpa_range,
+                                     match_root_decoder);
+       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),
-                       hpa_range->start, hpa_range->end);
-               return NULL;
+                       dev_name(&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)
@@ -3706,9 +3703,10 @@ 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);
+
+       if (IS_ERR(cxlrd))
+               return PTR_ERR(cxlrd);
 
        /*
         * Ensure that, if multiple threads race to construct_region()