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

[Liang Yang]

Hi Miquel,

Thanks for your quickly reply.

On 2018/12/11 15:54, Miquel Raynal wrote:
> Hi Liang,
>
> Liang Yang <liang.yang@xxxxxxxxxxx> wrote on Tue, 11 Dec 2018 09:56:25
> +0800:
>
> > 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.
>
> A suppose you meant "blank page"? If yes, then you don't need the
> helper to check for only-0xFF pages. If the controller tells you if the
> page was blank, then just check for that bit.

i think not. we need to return back the previous problem that how i can 
get the bitflips of one blank page. i think i need the helper.

> Thanks,
> MiquÃl
>
> .