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

[Liang Yang]

Hi Boris,

On 2018/12/11 16:39, Boris Brezillon wrote:
> On Tue, 11 Dec 2018 09:56:25 +0800
> Liang Yang <liang.yang@xxxxxxxxxxx> wrote:
>
> > Hi Miquel,
> >
> > On 2018/12/10 22:50, Miquel Raynal wrote:
> > > Hi Liang,
> > >
> > > Liang Yang <liang.yang@xxxxxxxxxxx> 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@xxxxxxxxxxx> 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?
> > >    
> > yes. when uncorrectable ECC error, i need firstly read out the ECC bytes
> > without ECC engine and then use the helper nand_check_erased_ecc_chunk
> > to check if blank page.
> > Of course, the precondition is without scrambler, or the bland page can
> > be detected by meson NFC.
>
> Yep, raw accessors should disable both the scrambler and the ECC
> engine (see what's done in sunxi_nand.c).

i see sunxi_nfc_hw_ecc_read_chunk and it will re-read the data for 
bitflips with scrambler off when ECC failed.
also we can do the same implementation and it seems to be the only answer.

> .