linux-kernel - Re: [RFC PATCH 13/20] cxl/mem: Refactor cxl pmem region auto-assembling

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Message-ID: <158453976.61750944183327.JavaMail.epsvc@epcpadp2new>
Date: Thu, 26 Jun 2025 15:33:47 +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 13/20] cxl/mem: Refactor cxl pmem region
 auto-assembling

On 23/06/25 10:20AM, Jonathan Cameron wrote:
>On Tue, 17 Jun 2025 18:09:37 +0530
>Neeraj Kumar <s.neeraj@...sung.com> wrote:
>
>> In 84ec985944ef3, For cxl pmem region auto-assembly after endpoint port
>> probing, cxl_nvd presence was required. And for cxl region persistency,
>> region creation happens during nvdimm_probe which need the completion
>> of endpoint probe.
>>
>> It is therefore refactored cxl pmem region auto-assembly after endpoint
>> probing to cxl mem probing
>>
>> Signed-off-by: Neeraj Kumar <s.neeraj@...sung.com>
>For ordering requirements this needs more eyes.  I've never cared that
>much about he persistency and auto assembly code so not something I have
>a good mental model of!
>

Sure, Will see how other maintainers responds to it. Thanks for your
feedback.

>
>> ---
>>  drivers/cxl/core/port.c | 38 ++++++++++++++++++++++++++++++++++++++
>>  drivers/cxl/cxl.h       |  1 +
>>  drivers/cxl/mem.c       | 27 ++++++++++++++++++---------
>>  drivers/cxl/port.c      | 38 --------------------------------------
>>  4 files changed, 57 insertions(+), 47 deletions(-)
>
>> diff --git a/drivers/cxl/mem.c b/drivers/cxl/mem.c
>> index 2f03a4d5606e..aaea4eb178ef 100644
>> --- a/drivers/cxl/mem.c
>> +++ b/drivers/cxl/mem.c
>
>> @@ -180,6 +171,24 @@ static int cxl_mem_probe(struct device *dev)
>>  			return rc;
>>  	}
>>
>> +	if (resource_size(&cxlds->pmem_res) && IS_ENABLED(CONFIG_CXL_PMEM)) {
>> +		rc = devm_cxl_add_nvdimm(parent_port, cxlmd);
>> +		if (rc) {
>> +			if (rc == -ENODEV)
>> +				dev_info(dev, "PMEM disabled by platform\n");
>> +			return rc;
>> +		}
>> +	}
>> +
>> +	/*
>> +	 * Now that all endpoint decoders are successfully enumerated, try to
>> +	 * assemble region autodiscovery from committed decoders.
>> +	 * Earlier it was part of cxl_endpoint_port_probe, So moved it here
>
>I would drop this history statement. Good to have in the patch description
>but no point in keeping it in the code. Just state what the requirements
>are now.
>

Okay, I will remove this and update commit message with the same

>> +	 * as cxl_nvd of the memdev needs to be available during the pmem
>> +	 * region auto-assembling
>> +	 */
>> +	cxl_region_discovery(cxlmd->endpoint);
>> +
>>  	/*
>>  	 * The kernel may be operating out of CXL memory on this device,
>
>
>