RE: [PATCH v3 2/9] EDAC/aspeed: Set the DIMM grain

[Ryan Chen]

> Subject: Re: [PATCH v3 2/9] EDAC/aspeed: Set the DIMM grain
> 
> On Wed, Sep 16, 2026 at 01:30:39PM +0800, Ryan Chen wrote:
> > The driver never sets dimm->grain, leaving it zero. Since commit
> > 3724ace582d9 ("EDAC/mc: Fix grain_bits calculation")
> > edac_raw_mc_handle_error() runs WARN_ON_ONCE(!e->grain) and forces
> the
> > grain to 1, so the first ECC error reported on any Aspeed BMC SoC
> > emits a warning splat, e.g. on the AST2600:
> >
> >   WARNING: CPU: 0 PID: 0 at drivers/edac/edac_mc.c:924
> edac_raw_mc_handle_error+0x4b4/0x604
> >   ...
> >   edac_raw_mc_handle_error from edac_mc_handle_error+0x364/0x4a8
> >   edac_mc_handle_error from count_rec+0xdc/0x124
> >   count_rec from mcr_isr+0x110/0x1e8
> 
> All of that is fine and dandy but you should talk about why the grain is chosen
> to be 16 here. The warning is just to make you choose a proper grain for your
> hw and doesn't need that much 'splainin'.

Got it.
v4 trims the warning down to a sentence and explains the value
instead: the controller records the address of a failing access with
16-byte granularity - MCR58 and MCR5C hold it in bits [30:4], with the
low four bits reserved.

> 
> > Fixes: 9b7e6242ee4e ("EDAC, aspeed: Add an Aspeed AST2500 EDAC
> > driver")
> > Signed-off-by: Ryan Chen <ryan_chen@xxxxxxxxxxxxxx>
> > Cc: stable@xxxxxxxxxxxxxxx
> 
> Is this really stable material and if so, why?

No. The error is still reported, only with the wrong granularity and a
one-off warning, so it doesn't meet the bar in
stable-kernel-rules.rst. I'll drop the tag and keep the Fixes: one.

Ryan