linux-kernel - Re: [PATCH] mtd: rawnand: mxc: set spare area size register explicitly

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Message-ID: <20180610131440.GA10544@botnar.kaiser.cx>
Date:   Sun, 10 Jun 2018 15:14:40 +0200
From:   Martin Kaiser <martin@...ser.cx>
To:     Miquel Raynal <miquel.raynal@...tlin.com>
Cc:     Boris Brezillon <boris.brezillon@...tlin.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Fabio Estevam <fabio.estevam@....com>,
        linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH] mtd: rawnand: mxc: set spare area size register
 explicitly

Hi Miquel,

Thus wrote Miquel Raynal (miquel.raynal@...tlin.com):

> > Usually, this register is updated from settings in the IIM fuses when
> > the system is booting from nand flash. For other boot media, however,

> s/nand/NAND

ok

> > +	/* spare area size in 16bit words */

> I thought I understood the problem with your commit message but
> then I don't get this comment. What's the link between 16-bit buses? Is
> this preset valid for both 8 and 16-bit bus width?

The register value is unrelated to the bus width.

> > +	writew(mtd->oobsize >> 1, NFC_V21_RSLTSPARE_AREA);
> > +

> If this is for dividing per two oobsize value,

That's exactly what I wanted to do: mtd->oobsize is in bytes, the
register value must be in 16bit words (the specification uses the term
half-words, I'll update the comment while at it).

> I would really prefer a '/ 2' and let the compiler optimize things.
> Unless the spec is explicit about some shifting of course.

Ok, I'll  use / 2 and resend the patch shortly.

Best regards,
Martin