Re: [PATCH 08/13] mtd: spinand: Reject 8D-8D-8D op_templates if octal_dtr_enale() is missing in manufacturer_op

[Apurva Nandan <a-nandan@xxxxxx>]

Hi Miquèl,

On 20/08/21 8:08 pm, Miquel Raynal wrote:
> Hi Apurva,
>
> Apurva Nandan <a-nandan@xxxxxx> wrote on Fri, 20 Aug 2021 19:24:34
> +0530:
>
> > Hi Miquèl,
> >
> > On 20/08/21 5:44 pm, Miquel Raynal wrote:
> > > Hi Apurva,
> > >
> > > Apurva Nandan <a-nandan@xxxxxx> wrote on Fri, 20 Aug 2021 16:56:50
> > > +0530:
> > >    
> > > > On 07/08/21 12:31 am, Miquel Raynal wrote:
> > > > > Hi Apurva,
> > > > >
> > > > > Apurva Nandan <a-nandan@xxxxxx> wrote on Tue, 13 Jul 2021 13:05:33
> > > > > +0000:
> > > > >     >>>> The SPI NAND core doesn't know how to switch the flash to Octal DTR
> > > > > > mode (i.e. which operations to perform). If the manufacturer hasn't
> > > > > > implemented the octal_dtr_enable() manufacturer_op, the SPI NAND core
> > > > > > wouldn't be able to switch to 8D-8D-8D mode and will also not be able
> > > > > > to run in 1S-1S-1S mode due to already selected 8D-8D-8D read/write
> > > > > > cache op_templates.
> > > > > >
> > > > > > So, avoid choosing a Octal DTR SPI op_template for read_cache,
> > > > > > write_cache and update_cache operations, if the manufacturer_op
> > > > > > octal_dtr_enable() is missing.
> > > > >
> > > > > After looking at your previous commit I don't see why this patch would
> > > > > be needed. octal_dtr_enable() only updates the mode when it succeeds so
> > > > > I don't think this patch is really needed.
> > > > >     >>
> > > > I added it to prevent any errors happening dues to a missing implementation of octal_dtr_enable() from manufacturer driver side.
> > > > So, if the manufacturers skips the octal_dtr_enable() implementation, we want the spinand core to run in 1s-1s-1s mode.
> > >
> > > I still don't get the point: you fail the probe if the octal bit is
> > > enabled but the manufacturer did not implement octal_dtr_enable(), so
> > > how could we have issues? Maybe I am overlooking something though, but
> > > this seemed completely redundant to my eyes so far.
> > >    
> >
> > Okay, I feel this may be redundant. This is for the case when the manufacturer has added Octal DTR read/write/update cache variants but hasn't implemented the octal_dtr_enable() method.
> >
> > Without this patch, the probe would fail, if the manufacturer did not implement octal_dtr_enable(). But after using this patch, spinand can still use the chip in 1s-1s-1s mode in that case and just skip the Octal DTR op variants during the selection. And also the probe would succeed.
>
> Unless I am overlooking something with this series applied
> (with or without this patch) the possibilities are:
> - no octal bit -> continue as before
> - octal bit and vendor callback -> uses octal mode
> - octal bit and no vendor callback -> will return an error from
> spinand_init_octal_dtr_enable() which will fail the probe (patch 7)
>
> Anyway we have a choice:
> - Either we consider the tables describing chips as pure descriptions
>    and we can support these chips in mode 1-1-1 (will require changes in
>    your series as this is not what you support as far as I understand
>    the code)
> - Or we consider these tables as "what is currently supported" and in
>    this case we just fail if one adds the octal bit without any callback
>    implementation.
>
> I think the latter is better for now. We can update this choice later
> if needed anyway.

Yes, I fully agree with the latter. I will drop this patch in the v2. 
Thanks!

> > > > Read/write/update op variant selection happens in select_op_variant(), much before octal_dtr_enable(). So just check if there is a definition of octal_dtr_enable in manufacturer ops and then only use 8D op variants.
> > > >
> > > > Removing this wouldn't break anything in the current implementation.
> > > > Do you think we should drop this?
> > > >   
> > > > > > Signed-off-by: Apurva Nandan <a-nandan@xxxxxx>
> > > > > > ---
> > > > > >     drivers/mtd/nand/spi/core.c | 7 ++++++-
> > > > > >     1 file changed, 6 insertions(+), 1 deletion(-)
> > > > > >
> > > > > > diff --git a/drivers/mtd/nand/spi/core.c b/drivers/mtd/nand/spi/core.c
> > > > > > index 19d8affac058..8711e887b795 100644
> > > > > > --- a/drivers/mtd/nand/spi/core.c
> > > > > > +++ b/drivers/mtd/nand/spi/core.c
> > > > > > @@ -1028,6 +1028,8 @@ static int spinand_manufacturer_match(struct spinand_device *spinand,
> > > > > >     		if (id[0] != manufacturer->id)
> > > > > >     			continue;
> > > > > >     >> +		spinand->manufacturer = manufacturer;
> > > > > > +
> > > > > >     		ret = spinand_match_and_init(spinand,
> > > > > >     					     manufacturer->chips,
> > > > > >     					     manufacturer->nchips,
> > > > > > @@ -1035,7 +1037,6 @@ static int spinand_manufacturer_match(struct spinand_device *spinand,
> > > > > >     		if (ret < 0)
> > > > > >     			continue;
> > > > > >     >> -		spinand->manufacturer = manufacturer;
> > > > > >     		return 0;
> > > > > >     	}
> > > > > >     	return -ENOTSUPP;
> > > > > > @@ -1097,6 +1098,10 @@ spinand_select_op_variant(struct spinand_device *spinand,
> > > > > >     		unsigned int nbytes;
> > > > > >     		int ret;
> > > > > >     >> +		if (spinand_op_is_octal_dtr(&op) &&
> > > > > > +		    !spinand->manufacturer->ops->octal_dtr_enable)
> > > > > > +			continue;
> > > > > > +
> > > > > >     		nbytes = nanddev_per_page_oobsize(nand) +
> > > > > >     			 nanddev_page_size(nand);
> > > > > >     > > Thanks,
> > > > > Miquèl
> > > > >
> > > > > ______________________________________________________
> > > > > Linux MTD discussion mailing list
> > > > > http://lists.infradead.org/mailman/listinfo/linux-mtd/
> > > > >     >>
> > > > Thanks,
> > > > Apurva Nandan
> > >
> > >
> > >
> > >
> > > Thanks,
> > > Miquèl
> > >    
> >
> > Thanks,
> > Apurva Nandan
>
> Thanks,
> Miquèl

Thanks,
Apurva Nandan