linux-kernel - Re: [PATCH v10 6/6] mtd: spi-nor: add support for Macronix Octal flash

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Message-ID: <CAPhrvRR6mkF1L2dBhsfwF7UmWG_0rHtf2Ry9+LiAt8xZbfsLZw@mail.gmail.com>
Date: Tue, 8 Oct 2024 11:38:27 +0800
From: Alvin Zhou <alvinzhou.tw@...il.com>
To: Tudor Ambarus <tudor.ambarus@...aro.org>
Cc: linux-mtd@...ts.infradead.org, linux-spi@...r.kernel.org, 
	linux-kernel@...r.kernel.org, pratyush@...nel.org, mwalle@...nel.org, 
	miquel.raynal@...tlin.com, richard@....at, vigneshr@...com, 
	broonie@...nel.org, chengminglin@...c.com.tw, leoyu@...c.com.tw, 
	AlvinZhou <alvinzhou@...c.com.tw>, JaimeLiao <jaimeliao@...c.com.tw>
Subject: Re: [PATCH v10 6/6] mtd: spi-nor: add support for Macronix Octal flash

Hi Tudor,

Tudor Ambarus <tudor.ambarus@...aro.org> 於 2024年10月2日 週三 下午3:45寫道：
>
>
>
> On 26.09.2024 17:19, AlvinZhou wrote:
> > From: AlvinZhou <alvinzhou@...c.com.tw>
> >
> > Adding manufacturer ID 0xC2 at the end of ID table
> > to allow manufacturer fixup to be applied for any
> > Macronix flashes instead of needing to list each
> > flash ID in the ID table.
> >
> > Such as macronix_nor_set_octal_dtr function in the
> > manufacturer fixup can be applied to any Macronix
> > Octal Flashes without the need to add the specific
> > ID in the ID table.
> >
> > Suggested-by: Michael Walle <mwalle@...nel.org>
> > Signed-off-by: JaimeLiao <jaimeliao@...c.com.tw>
> > Signed-off-by: AlvinZhou <alvinzhou@...c.com.tw>
> > ---
> >  drivers/mtd/spi-nor/macronix.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/mtd/spi-nor/macronix.c b/drivers/mtd/spi-nor/macronix.c
> > index f039819a5252..1a8ccebdfe0e 100644
> > --- a/drivers/mtd/spi-nor/macronix.c
> > +++ b/drivers/mtd/spi-nor/macronix.c
> > @@ -200,7 +200,9 @@ static const struct flash_info macronix_nor_parts[] = {
> >               .name = "mx25l3255e",
> >               .size = SZ_4M,
> >               .no_sfdp_flags = SECT_4K,
> > -     }
> > +     },
> > +     /* Need the manufacturer fixups, Keep this last */
>
> you have a capital letter in the middle of the sentence.
>
> I'll replace the comment with:
>
> /*
>
>  * This spares us of adding new flash entries for flashes that can be
>  * initialized solely based on the SFDP data, but still need the
>  * manufacturer hooks to set parameters that can't be discovered at SFDP
>  * parsing time.
>  */
>
> Which brings me to why you really set this. I remember SFDP contains
> tables with sequence of commands for enabling/disabling Octal DTR mode.
> Would you please remember me, why you didn't use those SFDP tables and
> implemented your own enable/disable methods?

While the SFDP does provide a sequence of commands to enable Octal
DDR mode, following this sequence forces the I/O driver strength to 50 ohms,
which causes I/O driver strength to be weak and and leads to read/write
issues, so we chose to use a fixup approach to enable/disable Octal DDR
mode.

Thanks,
Alvin