linux-kernel - Re: [RFC PATCH 18/20] cxl/pmem: Add support of cxl lsa 2.1 support in cxl pmem

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Message-ID: <45c254fe-fd74-46e7-bf06-5614810f7193@intel.com>
Date: Thu, 10 Jul 2025 10:18:27 -0700
From: Dave Jiang <dave.jiang@...el.com>
To: Neeraj Kumar <s.neeraj@...sung.com>, dan.j.williams@...el.com,
 dave@...olabs.net, jonathan.cameron@...wei.com, alison.schofield@...el.com,
 vishal.l.verma@...el.com, ira.weiny@...el.com
Cc: a.manzanares@...sung.com, nifan.cxl@...il.com, anisa.su@...sung.com,
 vishak.g@...sung.com, krish.reddy@...sung.com, arun.george@...sung.com,
 alok.rathore@...sung.com, neeraj.kernel@...il.com,
 linux-kernel@...r.kernel.org, linux-cxl@...r.kernel.org,
 nvdimm@...ts.linux.dev, gost.dev@...sung.com, cpgs@...sung.com
Subject: Re: [RFC PATCH 18/20] cxl/pmem: Add support of cxl lsa 2.1 support in
 cxl pmem



On 6/17/25 5:39 AM, Neeraj Kumar wrote:
> Add support of cxl lsa 2.1 using NDD_CXL_LABEL flag. It also creates cxl
> region based on region information parsed from LSA.
> 
> Signed-off-by: Neeraj Kumar <s.neeraj@...sung.com>
> ---
>  drivers/cxl/pmem.c | 59 ++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 59 insertions(+)
> 
> diff --git a/drivers/cxl/pmem.c b/drivers/cxl/pmem.c
> index ffcebb8d382f..2733d79b32d5 100644
> --- a/drivers/cxl/pmem.c
> +++ b/drivers/cxl/pmem.c
> @@ -58,6 +58,63 @@ static const struct attribute_group *cxl_dimm_attribute_groups[] = {
>  	NULL
>  };
>  
> +static int match_ep_decoder(struct device *dev, void *data)
> +{
> +	struct cxl_decoder *cxld = to_cxl_decoder(dev);
> +
> +	if (!cxld->region)
> +		return 1;
> +	else
> +		return 0;
> +}

return !cxld->region;


> +
> +static struct cxl_decoder *cxl_find_free_decoder(struct cxl_port *port)
> +{
> +	struct device *dev;
> +
> +	dev = device_find_child(&port->dev, NULL, match_ep_decoder);
> +	if (!dev)
> +		return NULL;
> +
> +	return to_cxl_decoder(dev);
> +}
> +
> +static int create_pmem_region(struct nvdimm *nvdimm)
> +{
> +	struct cxl_nvdimm *cxl_nvd;
> +	struct cxl_memdev *cxlmd;
> +	struct cxl_nvdimm_bridge *cxl_nvb;
> +	struct cxl_pmem_region_params *params;
> +	struct cxl_root_decoder *cxlrd;
> +	struct cxl_decoder *cxld;
> +	struct cxl_region *cxlr;
> +

probably need a lockdep_assert_held(&cxl_region_rwsem).

> +	if (!nvdimm)
> +		return -ENOTTY;

-ENODEV?

> +
> +	if (!nvdimm_has_cxl_region(nvdimm))
> +		return 0;
> +
> +	cxl_nvd = nvdimm_provider_data(nvdimm);
> +	params = nvdimm_get_cxl_region_param(nvdimm);
> +	cxlmd = cxl_nvd->cxlmd;
> +	cxl_nvb = cxlmd->cxl_nvb;
> +	cxlrd = cxlmd->cxlrd;
> +
> +	/* FIXME: Limitation: Region creation only when interleave way == 1 */
> +	if (params->nlabel == 1) {
> +		cxld = cxl_find_free_decoder(cxlmd->endpoint);
> +		cxlr = cxl_create_pmem_region(cxlrd, cxld, params,
> +				atomic_read(&cxlrd->region_id));
> +		if (IS_ERR(cxlr))
> +			dev_dbg(&cxlmd->dev, "Region Creation failed\n");

return PTR_ERR(cxlr); ?

> +	} else {
> +		dev_dbg(&cxlmd->dev, "Region Creation is not supported with iw > 1\n");
> +	}
> +
> +	return 0;
> +}
> +
>  static int cxl_nvdimm_probe(struct device *dev)
>  {
>  	struct cxl_nvdimm *cxl_nvd = to_cxl_nvdimm(dev);
> @@ -74,6 +131,7 @@ static int cxl_nvdimm_probe(struct device *dev)
>  		return rc;
>  
>  	set_bit(NDD_LABELING, &flags);
> +	set_bit(NDD_CXL_LABEL, &flags);

Ok here's the NDD_CXL_LABEL set. I think the driver should be probing the label index block and retrieve the label version and determine how to support from there instead of hard coding a flag. 

>  	set_bit(NDD_REGISTER_SYNC, &flags);
>  	set_bit(ND_CMD_GET_CONFIG_SIZE, &cmd_mask);
>  	set_bit(ND_CMD_GET_CONFIG_DATA, &cmd_mask);
> @@ -86,6 +144,7 @@ static int cxl_nvdimm_probe(struct device *dev)
>  		return -ENOMEM;
>  
>  	dev_set_drvdata(dev, nvdimm);
> +	create_pmem_region(nvdimm);
>  	return devm_add_action_or_reset(dev, unregister_nvdimm, nvdimm);
>  }
>