Re: [PATCH v2 3/6] EDAC/fsl_ddr: Fix bad bit shift operations

Borislav Petkov
2024-10-15T16:15:57Z

On Tue, Oct 15, 2024 at 11:31:41AM -0400, Frank Li wrote:
> I don't think it is urgent. In most system the return value is 0. I am not
> sure who caught it because patch already exist at downstream tree for a
> whole.

That current patch looks like it needs rethinking and making it sane - see
below.

> > > diff --git a/drivers/edac/fsl_ddr_edac.c b/drivers/edac/fsl_ddr_edac.c
> > > index 7a9fb1202f1a0..ccc13c2adfd6f 100644
> > > --- a/drivers/edac/fsl_ddr_edac.c
> > > +++ b/drivers/edac/fsl_ddr_edac.c
> > > @@ -338,11 +338,18 @@ static void fsl_mc_check(struct mem_ctl_info *mci)
> > > fsl_mc_printk(mci, KERN_ERR,
> > > "Faulty ECC bit: %d\n", bad_ecc_bit);
> > >
> > > - fsl_mc_printk(mci, KERN_ERR,
> > > - "Expected Data / ECC:\t%#8.8x_%08x / %#2.2x\n",
> > > - cap_high ^ (1 << (bad_data_bit - 32)),
> > > - cap_low ^ (1 << bad_data_bit),
> > > - syndrome ^ (1 << bad_ecc_bit));
> > > + if ((bad_data_bit > 0 && bad_data_bit < 32) && bad_ecc_bit > 0) {
> > > + fsl_mc_printk(mci, KERN_ERR,
> > > + "Expected Data / ECC:\t%#8.8x_%08x / %#2.2x\n",
> > > + cap_high, cap_low ^ (1 << bad_data_bit),
> > > + syndrome ^ (1 << bad_ecc_bit));
> > > + }
> > > + if (bad_data_bit >= 32 && bad_ecc_bit > 0) {
> > > + fsl_mc_printk(mci, KERN_ERR,
> > > + "Expected Data / ECC:\t%#8.8x_%08x / %#2.2x\n",
> > > + cap_high ^ (1 << (bad_data_bit - 32)),
> > > + cap_low, syndrome ^ (1 << bad_ecc_bit));
> > > + }
> >
> > This is getting unnecessarily clumsy than it should be. Please do the
> > following:
> >
> > if (bad_data_bit != 1 && bad_ecc_bit != -1) {
> >
> > // prep the values you need to print
> >
> > // do an exactly one fsl_mc_printk() with the prepared values.
> >
> > }
> >
> > Not have 4 fsl_mc_printks with a bunch of silly if-checks in front.

You missed the most important feedback. See above. ^^^^^^^

--
Regards/Gruss,
Boris.