linux-kernel - Re: [PATCH v4 1/2] EDAC/amd64: Set memory type per DIMM

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Message-ID: <Yf1LchOlECslWK2b@yaz-ubuntu>
Date:   Fri, 4 Feb 2022 15:51:14 +0000
From:   Yazen Ghannam <yazen.ghannam@....com>
To:     William Roche <william.roche@...cle.com>
Cc:     Borislav Petkov <bp@...en8.de>, linux-edac@...r.kernel.org,
        linux-kernel@...r.kernel.org, mchehab@...nel.org,
        tony.luck@...el.com, james.morse@....com, rric@...nel.org,
        Smita.KoralahalliChannabasappa@....com
Subject: Re: [PATCH v4 1/2] EDAC/amd64: Set memory type per DIMM

On Thu, Feb 03, 2022 at 04:46:44PM +0100, William Roche wrote:
> On 03/02/2022 15:09, Borislav Petkov wrote:
> 
> > On Thu, Feb 03, 2022 at 02:19:19PM +0100, William Roche wrote:
> > > As we are moving the dram_type cached date from pvt to umc for family >=
> > > 0x17, should we also add a small comment for the dram_type field in the
> > > amd64_pvt structure to indicate that ?
> > Who would be that comment for? People who are looking at the code, so
> > that they know which is which?
> 
> Yes, it could be a hint about the use case of this field.
> Of course we could be more complete and also comment the umc field use in
> this same structure that depends on the family higher or lower than 17 too.
> But I had the impression that the creation of a new dram_type cache field
> would be clarified by a comment on the old location, that's it.
> It's up to Yazen and you to include or not  this small addition about
> dram_type.
>

Thanks William for the review.

I think this is a good suggestion. I think it could be a bit more verbose.
Please see below.

Thanks,
Yazen

---
 
>From 028207619fb01008a2defc65183cbd30f98c021f Mon Sep 17 00:00:00 2001
From: Yazen Ghannam <yazen.ghannam@....com>
Date: Fri, 4 Feb 2022 15:10:52 +0000
Subject: [PATCH] EDAC/amd64: Comment on which dram_type to use

A copy of enum mem_type was added to struct amd64_umc so that memory
type can be properly identified on each independent Unified Memory
Controller.

Add a comment to the original struct amd64_pvt variable to indicate it
shouldn't be used on newer systems.

Signed-off-by: Yazen Ghannam <yazen.ghannam@....com>
---
 drivers/edac/amd64_edac.h | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/edac/amd64_edac.h b/drivers/edac/amd64_edac.h
index 6f8147abfa71..38e5ad95d010 100644
--- a/drivers/edac/amd64_edac.h
+++ b/drivers/edac/amd64_edac.h
@@ -397,7 +397,12 @@ struct amd64_pvt {
 	/* place to store error injection parameters prior to issue */
 	struct error_injection injection;
 
-	/* cache the dram_type */
+	/*
+	 * cache the dram_type
+	 *
+	 * NOTE: Don't use this for Family 17h and later.
+	 *	 Use dram_type in struct amd64_umc instead.
+	 */
 	enum mem_type dram_type;
 
 	struct amd64_umc *umc;	/* UMC registers */
-- 
2.25.1