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>
Reviewed-by: Dave Jiang <dave.jiang@intel.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 8244a27d0fd6..7d9d9b8f9eea 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -3212,6 +3212,38 @@ 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;
@@ -3386,29 +3418,17 @@ 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
@@ -3426,7 +3446,7 @@ 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);
 
@@ -3447,8 +3467,7 @@ 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

On Thu, Mar 06, 2025 at 05:44:42PM +0100, Robert Richter wrote:
> 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>
> Reviewed-by: Dave Jiang <dave.jiang@intel.com>
> Tested-by: Gregory Price <gourry@gourry.net>

Reviewed-by: Alison Schofield <alison.schofield@intel.com>

Robert Richter wrote:
> 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>
> Reviewed-by: Dave Jiang <dave.jiang@intel.com>
> Tested-by: Gregory Price <gourry@gourry.net>

Looks good to me:

Reviewed-by: Dan Williams <dan.j.williams@intel.com>

On Thursday, March 6, 2025 5:44:42 PM Central European Summer Time Robert Richter wrote:
> 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>
> Reviewed-by: Dave Jiang <dave.jiang@intel.com>
> Tested-by: Gregory Price <gourry@gourry.net>
> ---

Reviewed-by: Fabio M. De Francesco <fabio.m.de.francesco@linux.intel.com>

>  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 8244a27d0fd6..7d9d9b8f9eea 100644
> --- a/drivers/cxl/core/region.c
> +++ b/drivers/cxl/core/region.c
> @@ -3212,6 +3212,38 @@ 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;
> @@ -3386,29 +3418,17 @@ 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
> @@ -3426,7 +3446,7 @@ 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);
>  
> @@ -3447,8 +3467,7 @@ 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");
>