linux-kernel - Re: [PATCH v5 2/2] mtd: rawnand: meson: add support for Amlogic NAND flash controller

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Date:   Fri, 19 Oct 2018 10:10:33 +0200
From:   Boris Brezillon <boris.brezillon@...tlin.com>
To:     Liang Yang <liang.yang@...ogic.com>
Cc:     Jianxin Pan <jianxin.pan@...ogic.com>,
        <linux-mtd@...ts.infradead.org>, Rob Herring <robh@...nel.org>,
        Hanjie Lin <hanjie.lin@...ogic.com>,
        Victor Wan <victor.wan@...ogic.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        Richard Weinberger <richard@....at>,
        Yixun Lan <yixun.lan@...ogic.com>,
        <linux-kernel@...r.kernel.org>,
        Marek Vasut <marek.vasut@...il.com>,
        Jian Hu <jian.hu@...ogic.com>,
        Kevin Hilman <khilman@...libre.com>,
        Carlo Caione <carlo@...one.org>,
        <linux-amlogic@...ts.infradead.org>,
        Brian Norris <computersforpeace@...il.com>,
        David Woodhouse <dwmw2@...radead.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        Jerome Brunet <jbrunet@...libre.com>
Subject: Re: [PATCH v5 2/2] mtd: rawnand: meson: add support for Amlogic
 NAND flash controller

On Fri, 19 Oct 2018 15:29:05 +0800
Liang Yang <liang.yang@...ogic.com> wrote:

> > How about defining that the HW returns an array of __le64 instead and then
> > define the following macros which you can use after converting in the
> > CPU endianness
> > 
> > #define ECC_GET_PROTECTED_OOB_BYTE(x, y)	(((x) >> (8 * (1 + y)) & GENMASK(7, 0))
> > #define ECC_COMPLETE			BIT(31)
> > #define ECC_ERR_CNT(x)			(((x) >> 24) & GENMASK(5, 0))
> > 
> > (I'm not entirely sure the field positions are correct, but I'll let you
> > check that).
> >   
> ok. i think it should be:
> 
> #define ECC_GET_PROTECTED_OOB_BYTE(x, y)	(((x) >> (8 * y) &
> GENMASK(7, 0))
> 
> if x represents the u64 and y represents the index of the u64.

Absolutely.

> 
> 
> 
> >> +
> >> +#define PER_INFO_BYTE	(sizeof(struct meson_nfc_info_format))
> >> +
> >> +struct meson_nfc_nand_chip {
> >> +	struct list_head node;
> >> +	struct nand_chip nand;
> >> +	bool is_scramble;  
> > 
> > I think I already mentioned the NAND_NEED_SCRAMBLING flag []. Please
> > drop this field and test (chip->flags & NAND_NEED_SCRAMBLING) instead.
> >   
> em, i use NAND_NEED_SCRAMBLING and is_scramble is set:
> static int meson_nand_attach_chip(struct nand_chip *nand)
> {
> 	......
> 	meson_chip->is_scramble =
> 		(nand->options & NAND_NEED_SCRAMBLING) ? 1 : 0;
> 	......
> }

Why do you need to add a new field then? Just test
nand->options & NAND_NEED_SCRAMBLING directly or provide a helper
function that does that.