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: <1983025922.01750944303051.JavaMail.epsvc@epcpadp1new>
Date: Thu, 26 Jun 2025 16:11:27 +0530
From: Neeraj Kumar <s.neeraj@...sung.com>
To: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Cc: dan.j.williams@...el.com, dave@...olabs.net, dave.jiang@...el.com,
	alison.schofield@...el.com, vishal.l.verma@...el.com, ira.weiny@...el.com,
	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 23/06/25 10:48AM, Jonathan Cameron wrote:
>On Tue, 17 Jun 2025 18:09:42 +0530
>Neeraj Kumar <s.neeraj@...sung.com> 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;
>> +}
>> +
>> +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;
>> +
>> +	if (!nvdimm)
>> +		return -ENOTTY;
>
>As with other checks like this, it is useful to add a comment on when you can
>call this function with a null parameter.
>

Sure, Will fix it accordingly

>> +
>> +	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");
>> +	} else {
>> +		dev_dbg(&cxlmd->dev, "Region Creation is not supported with iw > 1\n");
>> +	}
>
>Flip logic to check for unhandled case first and also return an error if this happens
>rather than silently carrying on. dev_info() is appropriate here.
>

Thanks, Will fix it in V1

>> +
>> +	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);
>>  	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);
>>  }
>>
>