linux-kernel - Re: [PATCH] staging:mt29f_spinand: MT29F2G failing as only 16-bit arguments and variables used for addressing.

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Message-ID: <20180806141834.04ea7a57@bbrezillon>
Date:   Mon, 6 Aug 2018 14:18:34 +0200
From:   Boris Brezillon <boris.brezillon@...tlin.com>
To:     Dan Carpenter <dan.carpenter@...cle.com>
Cc:     Jheng-Jhong Wu <goodwater.wu@...il.com>,
        Palle Christensen <palle.christensen@...rosemi.com>,
        devel@...verdev.osuosl.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Arun Nagendran <arunrasppi@...il.com>,
        Miquel Raynal <miquel.raynal@...tlin.com>
Subject: Re: [PATCH] staging:mt29f_spinand: MT29F2G failing as only 16-bit
 arguments and variables used for addressing.

On Mon, 6 Aug 2018 15:01:37 +0300
Dan Carpenter <dan.carpenter@...cle.com> wrote:

> On Mon, Aug 06, 2018 at 01:46:48PM +0200, Boris Brezillon wrote:
> > Hi Dan,
> > 
> > On Wed, 1 Aug 2018 15:05:51 +0300
> > Dan Carpenter <dan.carpenter@...cle.com> wrote:
> >   
> > > On Wed, Aug 01, 2018 at 11:24:19AM +0800, Jheng-Jhong Wu wrote:  
> > > > For NAND flash chips with more than 1Gbit (e.g. MT29F2G) more than 16 bits
> > > > are necessary to address the correct page. The driver sets the address for
> > > > more than 16 bits, but it uses 16-bit arguments and variables (these are
> > > > page_id, block_id, row) to do address operations. Obviously, these
> > > > arguments and variables cannot deal with more than 16-bit address.
> > > > 
> > > > Signed-off-by: Jheng-Jhong Wu <goodwater.wu@...il.com>    
> > > 
> > > This seems reasonable...  It would be needed to make commit 6efb21d6d0e7
> > > ("staging:mt29f_spinand: MT29F2G failing as only 16 bits used for
> > > addressing.") work.  It also fixes a static checker warning.
> > > 
> > > My only concern is that the mtd/nand code seems to use -1 as a magical
> > > page_id.  For example:  
> > 
> > Yes, -1 means "don't issue the row/page address cycles", though I
> > don't think page can be -1 for NAND_CMD_READ{1,0} commands.
> >   
> 
> It sure looks like it can be in nand_exit_status_op()...

True, but nand_exit_status_op() won't be called here. It's only used
when the NAND controller driver is implementing ->exec_op() and needs
to do status polling, and from the micron NAND code that deals with raw
NAND chips with on-die ECC (the mt29f driver is supposed to deal with
SPI NANDs).

> 
> > Anyway, if you want this patch merged to fix a static checker warning,
> > I'm fine with that. In any case, I still plan to send a patch removing
> > this driver for v4.20, so, anyone using this driver should start
> > testing the new SPI NAND driver (drivers/mtd/nand/spi) and tweak/fix
> > the new implementation if needed.  
> 
> I don't think we should make the code more complicated than necessary
> just to make static checkers happy.  When you say "this driver", you
> mean the staging driver?

Yes.

> In that case, there is no need to revert
> commit 6efb21d6d0e7 ("staging:mt29f_spinand: MT29F2G failing as only 16
> bits used for addressing.").

Okay.