linux-kernel - Re: [PATCH V3 13/20] cxl/mem: Refactor cxl pmem region auto-assembling

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Message-ID: <361d0e84-9362-4389-a909-37878910b90f@intel.com>
Date: Mon, 6 Oct 2025 08:55:52 -0700
From: Dave Jiang <dave.jiang@...el.com>
To: Neeraj Kumar <s.neeraj@...sung.com>
Cc: linux-cxl@...r.kernel.org, nvdimm@...ts.linux.dev,
 linux-kernel@...r.kernel.org, gost.dev@...sung.com,
 a.manzanares@...sung.com, vishak.g@...sung.com, neeraj.kernel@...il.com,
 cpgs@...sung.com
Subject: Re: [PATCH V3 13/20] cxl/mem: Refactor cxl pmem region
 auto-assembling



On 9/29/25 6:30 AM, Neeraj Kumar wrote:
> On 23/09/25 03:37PM, Dave Jiang wrote:
>>
>>
>> On 9/17/25 6:41 AM, Neeraj Kumar wrote:
>>> In 84ec985944ef3, devm_cxl_add_nvdimm() sequence was changed and called
>>> before devm_cxl_add_endpoint(). It's because cxl pmem region auto-assembly
>>> used to get called at last in cxl_endpoint_port_probe(), which requires
>>> cxl_nvd presence.
>>>
>>> For cxl region persistency, region creation happens during nvdimm_probe
>>> which need the completion of endpoint probe.
>>>
>>> In order to accommodate both cxl pmem region auto-assembly and cxl region
>>> persistency, refactored following
>>>
>>> 1. Re-Sequence devm_cxl_add_nvdimm() after devm_cxl_add_endpoint(). This
>>>    will be called only after successful completion of endpoint probe.
>>>
>>> 2. Moved cxl pmem region auto-assembly from cxl_endpoint_port_probe() to
>>>    cxl_mem_probe() after devm_cxl_add_nvdimm(). It gurantees both the
>>>    completion of endpoint probe and cxl_nvd presence before its call.
>>
>> Given that we are going forward with this implementation [1] from Dan and drivers like the type2 enabling are going to be using it as well, can you please consider converting this change to Dan's mechanism instead of creating a whole new one?
>>
>> I think the region discovery can be done via the ops->probe() callback. Thanks.
>>
>> [1]: https://git.kernel.org/pub/scm/linux/kernel/git/cxl/cxl.git/commit/?h=for-6.18/cxl-probe-order&id=88aec5ea7a24da00dc92c7778df4851fe4fd3ec6
>>
>> DJ
>>
> 
> Sure, Let me revisit this.
> It seems [1] is there in seperate branch "for-6.18/cxl-probe-order", and not yet merged into next, right?

Right. I believe Smita and Alejandro are using that as well. Depending on who gets there first. We can setup an immutable branch at some point.

[1]: https://lore.kernel.org/linux-cxl/20250822034202.26896-1-Smita.KoralahalliChannabasappa@amd.com/T/#t

DJ

> 
> 
> Regards,
> Neeraj
>