linux-kernel - Re: [PATCH v5] EDAC/amd64: Fix size calculation for Non-Power-of-Two DIMMs

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Message-ID: <20250625145110.GAaFwM3ooyoFYsfgsf@fat_crate.local>
Date: Wed, 25 Jun 2025 16:51:10 +0200
From: Borislav Petkov <bp@...en8.de>
To: Avadhut Naik <avadhut.naik@....com>
Cc: linux-edac@...r.kernel.org, linux-kernel@...r.kernel.org,
	Žilvinas Žaltiena <zilvinas@...rix.lt>,
	Yazen Ghannam <yazen.ghannam@....com>
Subject: Re: [PATCH v5] EDAC/amd64: Fix size calculation for Non-Power-of-Two
 DIMMs

On Thu, May 29, 2025 at 08:50:04PM +0000, Avadhut Naik wrote:
> Each Chip-Select (CS) of a Unified Memory Controller (UMC) on AMD's
> modern Zen-based SOCs has an Address Mask and a Secondary Address Mask
> register associated with it. The amd64_edac module logs DIMM sizes on a
> per-UMC per-CS granularity during init using these two registers.
> 
> Currently, the module primarily considers only the Address Mask register
> for computing DIMM sizes. The Secondary Address Mask register is only
> considered for odd CS. Additionally, if it has been considered, the
> Address Mask register is ignored altogether for that CS. For
> power-of-two DIMMs i.e. DIMMs whose total capacity is a power of two
> (32GB, 64GB, etc.), this is not an issue since only the Address Mask
> register is used.
> 
> For non-power-of-two DIMMs i.e, DIMMs whose total capacity is not a power
> of two (48GB, 96GB, etc.), however, the Secondary Address Mask register
> is used in conjunction with the Address Mask register. However, since the
> module only considers either of the two registers for a CS, the size
> computed by the module is incorrect. The Secondary Address Mask register
> is not considered for even CS, and the Address Mask register is not
> considered for odd CS.
> 
> Introduce a new helper function so that both Address Mask and Secondary
> Address Mask registers are considered, when valid, for computing DIMM
> sizes. Furthermore, also rename some variables for greater clarity.
> 
> Fixes: 81f5090db843 ("EDAC/amd64: Support asymmetric dual-rank DIMMs")
> Reported-by: Žilvinas Žaltiena <zilvinas@...rix.lt>
> Closes: https://lore.kernel.org/dbec22b6-00f2-498b-b70d-ab6f8a5ec87e@natrix.lt
> Signed-off-by: Avadhut Naik <avadhut.naik@....com>
> Tested-by: Žilvinas Žaltiena <zilvinas@...rix.lt>
> Reviewed-by: Yazen Ghannam <yazen.ghannam@....com>
> Cc: stable@...r.kernel.org
> ---

Applied, thanks.

-- 
Regards/Gruss,
    Boris.

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