linux-kernel - RE: [PATCH v18 04/19] EDAC: Add memory repair control feature

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Message-ID: <7a758dde8f044a0d955413b379179b93@huawei.com>
Date: Tue, 14 Jan 2025 14:30:53 +0000
From: Shiju Jose <shiju.jose@...wei.com>
To: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
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Subject: RE: [PATCH v18 04/19] EDAC: Add memory repair control feature

>-----Original Message-----
>From: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
>Sent: 14 January 2025 13:47
>To: Shiju Jose <shiju.jose@...wei.com>
>Cc: linux-edac@...r.kernel.org; linux-cxl@...r.kernel.org; linux-
>acpi@...r.kernel.org; linux-mm@...ck.org; linux-kernel@...r.kernel.org;
>bp@...en8.de; tony.luck@...el.com; rafael@...nel.org; lenb@...nel.org;
>mchehab@...nel.org; dan.j.williams@...el.com; dave@...olabs.net; Jonathan
>Cameron <jonathan.cameron@...wei.com>; dave.jiang@...el.com;
>alison.schofield@...el.com; vishal.l.verma@...el.com; ira.weiny@...el.com;
>david@...hat.com; Vilas.Sridharan@....com; leo.duran@....com;
>Yazen.Ghannam@....com; rientjes@...gle.com; jiaqiyan@...gle.com;
>Jon.Grimm@....com; dave.hansen@...ux.intel.com;
>naoya.horiguchi@....com; james.morse@....com; jthoughton@...gle.com;
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>wschwartz@...erecomputing.com; dferguson@...erecomputing.com;
>wbs@...amperecomputing.com; nifan.cxl@...il.com; tanxiaofei
><tanxiaofei@...wei.com>; Zengtao (B) <prime.zeng@...ilicon.com>; Roberto
>Sassu <roberto.sassu@...wei.com>; kangkang.shen@...urewei.com;
>wanghuiqiang <wanghuiqiang@...wei.com>; Linuxarm
><linuxarm@...wei.com>
>Subject: Re: [PATCH v18 04/19] EDAC: Add memory repair control feature
>
>Em Mon, 6 Jan 2025 12:10:00 +0000
><shiju.jose@...wei.com> escreveu:
>
>> +What:		/sys/bus/edac/devices/<dev-
>name>/mem_repairX/repair_function
>> +Date:		Jan 2025
>> +KernelVersion:	6.14
>> +Contact:	linux-edac@...r.kernel.org
>> +Description:
>> +		(RO) Memory repair function type. For eg. post package repair,
>> +		memory sparing etc.
>> +		EDAC_SOFT_PPR - Soft post package repair
>> +		EDAC_HARD_PPR - Hard post package repair
>> +		EDAC_CACHELINE_MEM_SPARING - Cacheline memory sparing
>> +		EDAC_ROW_MEM_SPARING - Row memory sparing
>> +		EDAC_BANK_MEM_SPARING - Bank memory sparing
>> +		EDAC_RANK_MEM_SPARING - Rank memory sparing
>> +		All other values are reserved.
>> +
>> +What:		/sys/bus/edac/devices/<dev-
>name>/mem_repairX/persist_mode
>> +Date:		Jan 2025
>> +KernelVersion:	6.14
>> +Contact:	linux-edac@...r.kernel.org
>> +Description:
>> +		(RW) Read/Write the current persist repair mode set for a
>> +		repair function. Persist repair modes supported in the
>> +		device, based on the memory repair function is temporary
>> +		or permanent and is lost with a power cycle.
>> +		EDAC_MEM_REPAIR_SOFT - Soft repair function (temporary
>repair).
>> +		EDAC_MEM_REPAIR_HARD - Hard memory repair function
>(permanent repair).
>> +		All other values are reserved.
>> +
>
>After re-reading some things, I suspect that the above can be simplified a little
>bit by folding soft/hard PPR into a single element at /repair_function, and letting
>it clearer that persist_mode is valid only for PPR (I think this is the case, right?),
>e.g. something like:
persist_mode is valid for memory sparing features(atleast in CXL) as well.
In the case of CXL memory sparing, host has option to request either soft or hard sparing
in a flag when issue a memory sparing operation.

>
>	What:		/sys/bus/edac/devices/<dev-
>name>/mem_repairX/repair_function
>	...
>	Description:
>			(RO) Memory repair function type. For e.g. post
>package repair,
>			memory sparing etc. Valid values are:
>
>			- ppr - post package repair.
>			  Please define its mode via
>			  /sys/bus/edac/devices/<dev-
>name>/mem_repairX/persist_mode
>			- cacheline-sparing - Cacheline memory sparing
>			- row-sparing - Row memory sparing
>			- bank-sparing - Bank memory sparing
>			- rank-sparing - Rank memory sparing
>			- All other values are reserved.
>
>and define persist_mode in a different way:
Note: For return as decoded strings instead of raw value,  I need to add some extra callback function/s
in the edac/memory_repair.c  for these attributes  and which will reduce the current level of optimization done to
minimize the code size.
>
>	What:		/sys/bus/edac/devices/<dev-
>name>/mem_repairX/ppr_persist_mode
Same as above.  persist_mode is needed for memory sparing feature too.
>	...
>	Description:
>		(RW) Read/Write the current persist repair (PPR) mode set for a
>		post package repair function. Persist repair modes supported
>		in the device, based on the memory repair function is
>temporary
>		or permanent and is lost with a power cycle. Valid values are:
>
>		- repair-soft - Soft PPR function (temporary repair).
>		- repair-hard - Hard memory repair function (permanent
>repair).
>		- All other values are reserved.
>
>Thanks,
>Mauro

Thanks,
Shiju