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

From: Miquel Raynal <miquel.raynal@bootlin.com>
To: Liang Yang <liang.yang@amlogic.com>
Cc: Rob Herring <robh@kernel.org>,
	Hanjie Lin <hanjie.lin@amlogic.com>,
	Victor Wan <victor.wan@amlogic.com>,
	Jianxin Pan <jianxin.pan@amlogic.com>,
	Marek Vasut <marek.vasut@gmail.com>,
	Martin Blumenstingl <martin.blumenstingl@googlemail.com>,
	Richard Weinberger <richard@nod.at>,
	Neil Armstrong <narmstrong@baylibre.com>,
	Yixun Lan <yixun.lan@amlogic.com>,
	linux-kernel@vger.kernel.org,
	Boris Brezillon <boris.brezillon@bootlin.com>,
	Jian Hu <jian.hu@amlogic.com>,
	linux-mtd@lists.infradead.org,
	Kevin Hilman <khilman@baylibre.com>,
	Carlo Caione <carlo@caione.org>,
	linux-amlogic@lists.infradead.org,
	Brian Norris <computersforpeace@gmail.com>,
	David Woodhouse <dwmw2@infradead.org>,
	linux-arm-kernel@lists.infradead.org,
	Jerome Brunet <jbrunet@baylibre.com>
Subject: Re: [PATCH v7 2/2] mtd: rawnand: meson: add support for Amlogic NAND flash controller
Date: Mon, 10 Dec 2018 15:50:57 +0100	[thread overview]
Message-ID: <20181210155057.38788656@xps13> (raw)
In-Reply-To: <79a797c2-f37f-7f7c-e907-2d3c2283ec2d@amlogic.com>

Hi Liang,

Liang Yang <liang.yang@amlogic.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@amlogic.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

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