[PATCH v10 05/10] mtd: intel-dg: align 64bit read and write

[Usyskin, Alexander]

> Subject: Re: [PATCH v10 05/10] mtd: intel-dg: align 64bit read and write
> 
> On Thu, May 15, 2025 at 04:33:40PM +0300, Alexander Usyskin wrote:
> > GSC NVM controller HW errors on quad access overlapping 1K border.
> > Align 64bit read and write to avoid readq/writeq over 1K border.
> >
> > Acked-by: Miquel Raynal <miquel.raynal at bootlin.com>
> > Signed-off-by: Alexander Usyskin <alexander.usyskin at intel.com>
> > ---
> >  drivers/mtd/devices/mtd_intel_dg.c | 35
> ++++++++++++++++++++++++++++++
> >  1 file changed, 35 insertions(+)
> >
> > diff --git a/drivers/mtd/devices/mtd_intel_dg.c
> b/drivers/mtd/devices/mtd_intel_dg.c
> > index eedc0974bb5b..2f32ed311ffd 100644
> > --- a/drivers/mtd/devices/mtd_intel_dg.c
> > +++ b/drivers/mtd/devices/mtd_intel_dg.c
> > @@ -246,6 +246,24 @@ static ssize_t idg_write(struct intel_dg_nvm *nvm,
> u8 region,
> >  		len_s -= to_shift;
> >  	}
> >
> > +	if (!IS_ALIGNED(to, sizeof(u64)) &&
> > +	    ((to ^ (to + len_s)) & GENMASK(31, 10))) {
> > +		/*
> > +		 * Workaround reads/writes across 1k-aligned addresses
> > +		 * (start u32 before 1k, end u32 after)
> > +		 * as this fails on hardware.
> 
> If there's a spec definition, we usually mention workarounds with
> Wa_ID:platform so that they're easy to track. intel_workarounds.c
> is good reference for it.
> 
There is nothing in spec that I can find.
Not sure that i can formalize i as workaround.

> > +		 */
> > +		u32 data;
> > +
> > +		memcpy(&data, &buf[0], sizeof(u32));
> > +		idg_nvm_write32(nvm, to, data);
> > +		if (idg_nvm_error(nvm))
> > +			return -EIO;
> > +		buf += sizeof(u32);
> > +		to += sizeof(u32);
> > +		len_s -= sizeof(u32);
> > +	}
> > +
> >  	len8 = ALIGN_DOWN(len_s, sizeof(u64));
> >  	for (i = 0; i < len8; i += sizeof(u64)) {
> >  		u64 data;
> > @@ -303,6 +321,23 @@ static ssize_t idg_read(struct intel_dg_nvm *nvm,
> u8 region,
> >  		from += from_shift;
> >  	}
> >
> > +	if (!IS_ALIGNED(from, sizeof(u64)) &&
> > +	    ((from ^ (from + len_s)) & GENMASK(31, 10))) {
> > +		/*
> > +		 * Workaround reads/writes across 1k-aligned addresses
> > +		 * (start u32 before 1k, end u32 after)
> > +		 * as this fails on hardware.
> > +		 */
> > +		u32 data = idg_nvm_read32(nvm, from);
> > +
> > +		if (idg_nvm_error(nvm))
> > +			return -EIO;
> > +		memcpy(&buf[0], &data, sizeof(data));
> > +		len_s -= sizeof(u32);
> > +		buf += sizeof(u32);
> > +		from += sizeof(u32);
> > +	}
> > +
> >  	len8 = ALIGN_DOWN(len_s, sizeof(u64));
> >  	for (i = 0; i < len8; i += sizeof(u64)) {
> >  		u64 data = idg_nvm_read64(nvm, from + i);
> > --
> > 2.43.0
> >