linux-kernel - Re: [PATCH v7 2/2] mtd: rawnand: meson: add support for Amlogic NAND flash controller

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Message-ID: <20181210155057.38788656@xps13>
Date:   Mon, 10 Dec 2018 15:50:57 +0100
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Liang Yang <liang.yang@...ogic.com>
Cc:     Boris Brezillon <boris.brezillon@...tlin.com>,
        Jianxin Pan <jianxin.pan@...ogic.com>,
        <linux-mtd@...ts.infradead.org>, Yixun Lan <yixun.lan@...ogic.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Marek Vasut <marek.vasut@...il.com>,
        Richard Weinberger <richard@....at>,
        Jerome Brunet <jbrunet@...libre.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        Carlo Caione <carlo@...one.org>,
        Kevin Hilman <khilman@...libre.com>,
        Rob Herring <robh@...nel.org>, Jian Hu <jian.hu@...ogic.com>,
        Hanjie Lin <hanjie.lin@...ogic.com>,
        Victor Wan <victor.wan@...ogic.com>,
        <linux-amlogic@...ts.infradead.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v7 2/2] mtd: rawnand: meson: add support for Amlogic
 NAND flash controller

Hi Liang,

Liang Yang <liang.yang@...ogic.com> wrote on Mon, 10 Dec 2018 20:12:39
+0800:

> On 2018/12/10 19:38, Boris Brezillon wrote:
> > On Mon, 10 Dec 2018 19:23:46 +0800
> > Liang Yang <liang.yang@...ogic.com> wrote:
> >   
> >>>> +			mtd->ecc_stats.failed++;
> >>>> +			continue;
> >>>> +		}
> >>>> +		mtd->ecc_stats.corrected += ECC_ERR_CNT(*info);
> >>>> +		bitflips = max_t(u32, bitflips, ECC_ERR_CNT(*info));
> >>>> +	}  
> >>>
> >>> Are you sure you handle correctly empty pages with bf?  
> >>>    >> if scramble is enable, i would say yes here.  
> >> when scramble is disabled, i am considering how to use the helper
> >> nand_check_erased_ecc_chunk, but it seems that i can't get the ecc
> >> bytes which is caculated by ecc engine.by the way, nfc dma doesn't send
> >> out the ecc parity bytes.  
> > 
> > Even if the ECC engine is disabled?
> >   
> No.
> When ECC engine is disabled, it can read the ecc parity bytes ; but there is another problem that i need to consider how code struct looks better when reading error with ecc opened and then try to raw read.
> Is there a good idea?

When reading with ECC enabled, in case of uncorrectable error you
must re-read without ECC, then check if the page is empty or not with
the core helpers (nand_check_erased_*()).

Is this what you meant?

Thanks,
Miquèl