Re: [PATCH 6.1.y] EDAC/amd64: Fix size calculation for Non-Power-of-Two DIMMs

[Greg KH <gregkh@linuxfoundation.org>]

On Tue, Jul 01, 2025 at 05:10:32PM +0000, Avadhut Naik wrote:
> Each Chip-Select (CS) of a Unified Memory Controller (UMC) on AMD 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")
> Closes: https://lore.kernel.org/dbec22b6-00f2-498b-b70d-ab6f8a5ec87e@natrix.lt
> Reported-by: Žilvinas Žaltiena <zilvinas@natrix.lt>
> Signed-off-by: Avadhut Naik <avadhut.naik@amd.com>
> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
> Reviewed-by: Yazen Ghannam <yazen.ghannam@amd.com>
> Tested-by: Žilvinas Žaltiena <zilvinas@natrix.lt>
> Cc: stable@vger.kernel.org
> Link: https://lore.kernel.org/20250529205013.403450-1-avadhut.naik@amd.com
> (cherry picked from commit a3f3040657417aeadb9622c629d4a0c2693a0f93)
> Signed-off-by: Avadhut Naik <avadhut.naik@amd.com>

This was not a clean cherry-pick at all.  Please document what you did
differently from the original commit please.

thanks,

greg k-h