linux-kernel - Re: [PATCH 4/4] EDAC/amd64: Add DDR5 support and related register changes

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Date:   Tue, 14 Dec 2021 17:22:20 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Yazen Ghannam <yazen.ghannam@....com>
Cc:     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,
        william.roche@...cle.com
Subject: Re: [PATCH 4/4] EDAC/amd64: Add DDR5 support and related register
 changes

On Mon, Dec 13, 2021 at 05:46:55PM +0000, Yazen Ghannam wrote:
> Yeah, sorry it's not clear. The purpose of the flag is to indicate some minor
> changes that show up with future systems like register offsets changes, etc. I
> didn't want to tie the name to a specific model or core name. I went with DDR5
> as a new feature that shows up with these changes, but they're not directly
> tied to DDR5.
> 
> But yes, a system may support DDR5 and DDR4. And this can be detected from the
> hardware.
> 
> What do you think about calling the flag "uses_f19h_m10h_offsets" or something
> like that? I was trying to avoid family/model in the name, but the code
> already does this all over. And the convention has been to call something by
> the first family/model where it shows up.

Good question.

So AFAIU, these register offset changes are probably going to propagate
beyond F19M10... In any case, they won't be tied to the family/model
so your flag idea is in the right direction, AFAICT. I'd do something
shorter, though, so that the code accessing it is short'n'sweet:

	if (pvt->flags.f19h_regs_ng)		- "new generation" regs :-)

or even

	if (pvt->flags.zn_new_regs_fmt)

or whatever that's called. The GPU UMC is called UMC_v2 so I guess

	if (pvt->flags.zn_regs_v2)

:-)

You get the idea...

With an ample explanation in a comment what that means, ofc.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette