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Date:   Fri, 20 Aug 2021 14:14:13 +0200
From:   Miquel Raynal <miquel.raynal@bootlin.com>
To:     Apurva Nandan <a-nandan@ti.com>
Cc:     Richard Weinberger <richard@nod.at>,
        Vignesh Raghavendra <vigneshr@ti.com>,
        Mark Brown <broonie@kernel.org>,
        Patrice Chotard <patrice.chotard@foss.st.com>,
        Boris Brezillon <boris.brezillon@collabora.com>,
        <linux-mtd@lists.infradead.org>, <linux-kernel@vger.kernel.org>,
        <linux-spi@vger.kernel.org>, Pratyush Yadav <p.yadav@ti.com>
Subject: Re: [PATCH 08/13] mtd: spinand: Reject 8D-8D-8D op_templates if
 octal_dtr_enale() is missing in manufacturer_op
Message-ID: <20210820141413.6c519255@xps13>
In-Reply-To: <4d428465-59d7-6771-8344-c5090add2a06@ti.com>
References: <20210713130538.646-1-a-nandan@ti.com>
        <20210713130538.646-9-a-nandan@ti.com>
        <20210806210146.3358a85b@xps13>
        <4d428465-59d7-6771-8344-c5090add2a06@ti.com>
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Hi Apurva,

Apurva Nandan <a-nandan@ti.com> 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@ti.com> 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.

> 
> 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@ti.com>
> >> ---
> >>   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