Re: [PATCH v4 02/14] cxl/pci: Moving code in cxl_hdm_decode_init()

[Jonathan Cameron <Jonathan.Cameron@huawei.com>]

On Thu, 6 Mar 2025 17:44:36 +0100
Robert Richter <rrichter@amd.com> wrote:

> Commit 3f9e07531778 ("cxl/pci: simplify the check of mem_enabled in
> cxl_hdm_decode_init()") changed the code flow in this function. The
> root port is determined before a check to leave the function. Since
> the root port is not used by the check it can be moved to run the
> check first. This improves code readability and avoids unnesessary
> code execution.
> 
> Signed-off-by: Robert Richter <rrichter@amd.com>
> Reviewed-by: Gregory Price <gourry@gourry.net>
> Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>
> Tested-by: Gregory Price <gourry@gourry.net>
> ---
>  drivers/cxl/core/pci.c | 16 ++++++++--------
>  1 file changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/cxl/core/pci.c b/drivers/cxl/core/pci.c
> index 33c3bdd35b24..6386e84e51a4 100644
> --- a/drivers/cxl/core/pci.c
> +++ b/drivers/cxl/core/pci.c
> @@ -419,14 +419,6 @@ int cxl_hdm_decode_init(struct cxl_dev_state *cxlds, struct cxl_hdm *cxlhdm,
>  	if (!hdm)
>  		return -ENODEV;
>  
> -	root = to_cxl_port(port->dev.parent);
> -	while (!is_cxl_root(root) && is_cxl_port(root->dev.parent))
> -		root = to_cxl_port(root->dev.parent);
> -	if (!is_cxl_root(root)) {
> -		dev_err(dev, "Failed to acquire root port for HDM enable\n");
> -		return -ENODEV;
> -	}
> -
>  	if (!info->mem_enabled) {
>  		rc = devm_cxl_enable_hdm(&port->dev, cxlhdm);
>  		if (rc)
> @@ -435,6 +427,14 @@ int cxl_hdm_decode_init(struct cxl_dev_state *cxlds, struct cxl_hdm *cxlhdm,
>  		return devm_cxl_enable_mem(&port->dev, cxlds);
>  	}
>  
> +	root = to_cxl_port(port->dev.parent);
> +	while (!is_cxl_root(root) && is_cxl_port(root->dev.parent))
> +		root = to_cxl_port(root->dev.parent);
> +	if (!is_cxl_root(root)) {
> +		dev_err(dev, "Failed to acquire root port for HDM enable\n");

Is this error message suffering from code rot?  In the path where
root is used, use no HDM enabling occurs.

> +		return -ENODEV;
> +	}
> +
>  	for (i = 0, allowed = 0; i < info->ranges; i++) {
>  		struct device *cxld_dev;
>