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Date:   Sun, 10 May 2020 10:41:45 +0200
From:   Boris Brezillon <boris.brezillon@collabora.com>
To:     Miquel Raynal <miquel.raynal@bootlin.com>
Cc:     Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        <devicetree@vger.kernel.org>, Richard Weinberger <richard@nod.at>,
        Vignesh Raghavendra <vigneshr@ti.com>,
        Tudor Ambarus <Tudor.Ambarus@microchip.com>,
        <linux-mtd@lists.infradead.org>,
        Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
        Michal Simek <monstr@monstr.eu>,
        Naga Sureshkumar Relli <nagasure@xilinx.com>
Subject: Re: [PATCH v4 7/8] mtd: rawnand: arasan: Add new Arasan NAND
 controller
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In-Reply-To: <20200510103547.7399eba3@xps13>
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        <20200508171339.8052-8-miquel.raynal@bootlin.com>
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On Sun, 10 May 2020 10:35:47 +0200
Miquel Raynal <miquel.raynal@bootlin.com> wrote:

> Hi Boris,
> 
> Boris Brezillon <boris.brezillon@collabora.com> wrote on Sun, 10 May
> 2020 09:02:30 +0200:
> 
> > On Fri,  8 May 2020 19:13:38 +0200
> > Miquel Raynal <miquel.raynal@bootlin.com> wrote:
> >   
> > > +static int anfc_len_to_steps(struct nand_chip *chip, unsigned int len)
> > > +{
> > > +	unsigned int steps = 1, pktsize = len;
> > > +
> > > +	while (pktsize > ANFC_MAX_PKT_SIZE) {
> > > +		steps *= 2;
> > > +		pktsize = DIV_ROUND_UP(len, steps);
> > > +	}    
> > 
> > 
> > Same here, you shouldn't have a round_up() but instead complain if
> > "len != pkt_size * steps"
> > 
> > 	if (len % 4)
> > 		return -ENOTSUPP;  
> 
> This is not possible, we need unaligned accesses for NAND detection.

Duh, this really calls for a comment saying how wrong this is and how
it should be fixed (discussions we had about data size constraints and
the 'can-issue-more' flag on data_in/out instructions).

> 
> > 
> > 	if (len < ANFC_MAX_PKT_SIZE)
> > 		return len;
> > 
> > 	for (steps = 2; steps < ANFC_MAX_STEPS; steps *= 2) {
> > 		pkt_size = len / steps;
> > 		if (pkt_size <= ANFC_MAX_PKT_SIZE)
> > 			break;
> > 	}
> > 
> > 	if (pkt_size * steps != len)
> > 		return -ENOTSUPP;
> > 
> > 	return pkt_size;  
> 
> The rest looks fine, I will change it and also add these checks in
> ->exec_op() check_nonly path.