Re: [PATCH V5 16/17] cxl/pmem_region: Create pmem region using information parsed from LSA

Jonathan Cameron
2026-01-15T18:28:35Z

On Fri, 9 Jan 2026 18:14:36 +0530
Neeraj Kumar <s.neeraj@samsung.com> wrote:

> create_pmem_region() creates CXL region based on region information
> parsed from the Label Storage Area (LSA). This routine requires cxl
> endpoint decoder and root decoder. Add cxl_find_root_decoder_by_port()
> and cxl_find_free_ep_decoder() to find the root decoder and a free
> endpoint decoder respectively.
>
> Signed-off-by: Neeraj Kumar <s.neeraj@samsung.com>
Hi Neeraj,

Just a few minor things.

Jonathan

> diff --git a/drivers/cxl/core/pmem_region.c b/drivers/cxl/core/pmem_region.c
> index 53d3d81e9676..4a8cf8322cf0 100644
> --- a/drivers/cxl/core/pmem_region.c
> +++ b/drivers/cxl/core/pmem_region.c
> @@ -287,3 +287,139 @@ int devm_cxl_add_pmem_region(struct cxl_region *cxlr)
> cxlr->cxl_nvb = NULL;
> return rc;
> }
> +
> +static int match_root_decoder_by_dport(struct device *dev, const void *data)
> +{
> + const struct cxl_port *ep_port = data;
> + struct cxl_root_decoder *cxlrd;
> + struct cxl_port *root_port;
> + struct cxl_decoder *cxld;
> + struct cxl_dport *dport;
> + bool dport_matched = false;
> +
> + if (!is_root_decoder(dev))
> + return 0;
> +
> + cxld = to_cxl_decoder(dev);
> + if (!(cxld->flags & CXL_DECODER_F_PMEM))
> + return 0;
> +
> + cxlrd = to_cxl_root_decoder(dev);
> +
> + root_port = cxlrd_to_port(cxlrd);
> + dport = cxl_find_dport_by_dev(root_port, ep_port->host_bridge);
> + if (!dport)
> + return 0;
> +
There is a fairly standard way to check if a loop matched without
needing a boolean. Just check if the exit condition was reached.

drop declaration of i out of here.
> + for (int i = 0; i < cxlrd->cxlsd.nr_targets; i++) {
> + if (dport == cxlrd->cxlsd.target[i]) {
> + dport_matched = true;
No need for this.
> + break;
> + }
> + }
> +
> + if (!dport_matched)
if (i == cxlrd->cxlsd.nr_targets)
return 0;

> + return 0;
> +
> + return is_root_decoder(dev);
> +}
> +
> +/**
> + * cxl_find_root_decoder_by_port() - find a cxl root decoder on cxl bus
> + * @port: any descendant port in CXL port topology
> + * @cxled: endpoint decoder
> + *
> + * Caller of this function must call put_device() when done as a device ref
> + * is taken via device_find_child()
> + */
> +static struct cxl_root_decoder *
> +cxl_find_root_decoder_by_port(struct cxl_port *port,
> + struct cxl_endpoint_decoder *cxled)
> +{
> + struct cxl_root *cxl_root __free(put_cxl_root) = find_cxl_root(port);
> + struct cxl_port *ep_port = cxled_to_port(cxled);
> + struct device *dev;
> +
> + if (!cxl_root)
> + return NULL;
> +
> + dev = device_find_child(&cxl_root->port.dev, ep_port,
> + match_root_decoder_by_dport);
> + if (!dev)
> + return NULL;
> +
> + return to_cxl_root_decoder(dev);
> +}

> +void create_pmem_region(struct nvdimm *nvdimm)
> +{
> + struct cxl_region *cxlr;
> + struct cxl_memdev *cxlmd;
> + struct cxl_nvdimm *cxl_nvd;
> + struct cxl_endpoint_decoder *cxled;
> + struct cxl_pmem_region_params *params;

CXL tends to be reverse xmas tree and good to stick to local style.

> +
> + if (!nvdimm_has_cxl_region(nvdimm))
> + return;
> +
> + lockdep_assert_held(&cxl_rwsem.region);
> + cxl_nvd = nvdimm_provider_data(nvdimm);
> + params = nvdimm_get_cxl_region_param(nvdimm);
> + cxlmd = cxl_nvd->cxlmd;
> +
> + /* TODO: Region creation support only for interleave way == 1 */
> + if (!(params->nlabel == 1)) {
> + dev_dbg(&cxlmd->dev,
> + "Region Creation is not supported with iw > 1\n");
> + return;
> + }
> +
> + struct cxl_decoder *cxld __free(put_cxl_decoder) =
> + cxl_find_free_ep_decoder(cxlmd->endpoint);
> + if (!cxld) {
> + dev_err(&cxlmd->dev, "CXL endpoint decoder not found\n");
> + return;
> + }
> +
> + cxled = to_cxl_endpoint_decoder(&cxld->dev);
> +
> + struct cxl_root_decoder *cxlrd __free(put_cxl_root_decoder) =
> + cxl_find_root_decoder_by_port(cxlmd->endpoint, cxled);
> + if (!cxlrd) {
> + dev_err(&cxlmd->dev, "CXL root decoder not found\n");
> + return;
> + }
> +
> + cxlr = cxl_create_region(cxlrd, CXL_PARTMODE_PMEM,
> + atomic_read(&cxlrd->region_id),
> + params, cxled);
> + if (IS_ERR(cxlr))
> + dev_warn(&cxlmd->dev, "Region Creation failed\n");
> +}
> +EXPORT_SYMBOL_NS_GPL(create_pmem_region, "CXL");