linux-kernel - Re: [PATCH 19/19] EDAC, Documentation: Describe CPER module definition and DIMM ranks

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Date:   Fri, 11 Oct 2019 08:29:13 -0300
From:   Mauro Carvalho Chehab <mchehab+samsung@...nel.org>
To:     Robert Richter <rrichter@...vell.com>
Cc:     Borislav Petkov <bp@...en8.de>, Tony Luck <tony.luck@...el.com>,
        Jonathan Corbet <corbet@....net>,
        James Morse <james.morse@....com>,
        "linux-edac@...r.kernel.org" <linux-edac@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>
Subject: Re: [PATCH 19/19] EDAC, Documentation: Describe CPER module
 definition and DIMM ranks

Em Thu, 10 Oct 2019 20:25:42 +0000
Robert Richter <rrichter@...vell.com> escreveu:

> Update on CPER DIMM naming convention and DIMM ranks.
> 
> Signed-off-by: Robert Richter <rrichter@...vell.com>

Reviewed-by: Mauro Carvalho Chehab <mchehab+samsung@...nel.org>

> ---
>  Documentation/admin-guide/ras.rst | 31 +++++++++++++++++++------------
>  1 file changed, 19 insertions(+), 12 deletions(-)
> 
> diff --git a/Documentation/admin-guide/ras.rst b/Documentation/admin-guide/ras.rst
> index 2b20f5f7380d..26e02a59f0f4 100644
> --- a/Documentation/admin-guide/ras.rst
> +++ b/Documentation/admin-guide/ras.rst
> @@ -330,9 +330,12 @@ There can be multiple csrows and multiple channels.
>  
>  .. [#f4] Nowadays, the term DIMM (Dual In-line Memory Module) is widely
>    used to refer to a memory module, although there are other memory
> -  packaging alternatives, like SO-DIMM, SIMM, etc. Along this document,
> -  and inside the EDAC system, the term "dimm" is used for all memory
> -  modules, even when they use a different kind of packaging.
> +  packaging alternatives, like SO-DIMM, SIMM, etc. The UEFI
> +  specification (Version 2.7) defines a memory module in the Common
> +  Platform Error Record (CPER) section to be an SMBIOS Memory Device
> +  (Type 17). Along this document, and inside the EDAC system, the term
> +  "dimm" is used for all memory modules, even when they use a
> +  different kind of packaging.
>  
>  Memory controllers allow for several csrows, with 8 csrows being a
>  typical value. Yet, the actual number of csrows depends on the layout of
> @@ -349,12 +352,14 @@ controllers. The following example will assume 2 channels:
>  	|            |  ``ch0``  |  ``ch1``  |
>  	+============+===========+===========+
>  	| ``csrow0`` |  DIMM_A0  |  DIMM_B0  |
> -	+------------+           |           |
> -	| ``csrow1`` |           |           |
> +	|            |   rank0   |   rank0   |
> +	+------------+     -     |     -     |
> +	| ``csrow1`` |   rank1   |   rank1   |
>  	+------------+-----------+-----------+
>  	| ``csrow2`` |  DIMM_A1  | DIMM_B1   |
> -	+------------+           |           |
> -	| ``csrow3`` |           |           |
> +	|            |   rank0   |   rank0   |
> +	+------------+     -     |     -     |
> +	| ``csrow3`` |   rank1   |   rank1   |
>  	+------------+-----------+-----------+
>  
>  In the above example, there are 4 physical slots on the motherboard
> @@ -374,11 +379,13 @@ which the memory DIMM is placed. Thus, when 1 DIMM is placed in each
>  Channel, the csrows cross both DIMMs.
>  
>  Memory DIMMs come single or dual "ranked". A rank is a populated csrow.
> -Thus, 2 single ranked DIMMs, placed in slots DIMM_A0 and DIMM_B0 above
> -will have just one csrow (csrow0). csrow1 will be empty. On the other
> -hand, when 2 dual ranked DIMMs are similarly placed, then both csrow0
> -and csrow1 will be populated. The pattern repeats itself for csrow2 and
> -csrow3.
> +In the example above 2 dual ranked DIMMs are similarly placed. Thus,
> +both csrow0 and csrow1 are populated. On the other hand, when 2 single
> +ranked DIMMs are placed in slots DIMM_A0 and DIMM_B0, then they will
> +have just one csrow (csrow0) and csrow1 will be empty. The pattern
> +repeats itself for csrow2 and csrow3. Also note that some memory
> +controller doesn't have any logic to identify the memory module, see
> +``rankX`` directories below.
>  
>  The representation of the above is reflected in the directory
>  tree in EDAC's sysfs interface. Starting in directory



Thanks,
Mauro