Re: [PATCH v2 5/5] mtd: rawnand: mtk: Setup empty page threshold correctly

[xiaolei li <xiaolei.li@xxxxxxxxxxxx>]

Hi Miquel,

On Tue, 2019-04-30 at 14:17 +0200, Miquel Raynal wrote:
> Hi Xiaolei,
> 
> Xiaolei Li <xiaolei.li@xxxxxxxxxxxx> wrote on Tue, 30 Apr 2019 18:02:50
> +0800:
> 
> > MTK NAND Controller has the ability to check whether read data are
> > mostly 0xff by comparing zero bit count of read data with empty
> > threshold automatically.
> > 
> > But now we never set this threshold and always make it be default value
> > which is 10.
> > 
> > This patch fixes this problem by setting empty threshold as the product
> > of read sector count and ECC strength.
> 
> Are you sure it is not a per-sector value?
Frankly, I also think it should be a per-sector value.

But MTK NAND Controller cannot check 0xff by sector. It counts zero bit
through all read data. So, I set the empty threshold as the product of
read sector count and ECC strength.

> 
> Did you use nandbiterrs to validate?
Yes. I ever did nandbiterrs test, and it passed.

> 
> > 
> > Fixes: 1d6b1e464950 ("mtd: mediatek: driver for MTK Smart Device")
> > Signed-off-by: Xiaolei Li <xiaolei.li@xxxxxxxxxxxx>
> > ---
> >  drivers/mtd/nand/raw/mtk_nand.c | 9 +++++++++
> >  1 file changed, 9 insertions(+)
> > 
> > diff --git a/drivers/mtd/nand/raw/mtk_nand.c b/drivers/mtd/nand/raw/mtk_nand.c
> > index 48759af5c058..b56965328771 100644
> > --- a/drivers/mtd/nand/raw/mtk_nand.c
> > +++ b/drivers/mtd/nand/raw/mtk_nand.c
> > @@ -94,6 +94,7 @@
> >  #define NFI_MASTER_STA		(0x224)
> >  #define		MASTER_STA_MASK		(0x0FFF)
> >  #define NFI_EMPTY_THRESH	(0x23C)
> > +#define		EMPTY_THRESH_MASK	GENMASK(7, 0)
> >  
> >  #define MTK_NAME		"mtk-nand"
> >  #define KB(x)			((x) * 1024UL)
> > @@ -947,6 +948,14 @@ static int mtk_nfc_read_subpage(struct mtd_info *mtd, struct nand_chip *chip,
> >  		return -EINVAL;
> >  	}
> >  
> > +	/**
> 
>         /*
> 
> > +	 * Setup empty threshold as the product of sector count
> > +	 * and ECC strength
> > +	 */
> > +	reg = sectors * chip->ecc.strength;
> > +	reg = min_t(unsigned int, reg, EMPTY_THRESH_MASK);
> > +	nfi_writel(nfc, reg, NFI_EMPTY_THRESH);
> > +
> >  	reg = nfi_readw(nfc, NFI_CNFG);
> >  	reg |= CNFG_READ_EN | CNFG_DMA_BURST_EN | CNFG_AHB;
> >  	if (!raw) {
> 
> 
> Thanks,
> Miquèl

Thanks,
Xiaolei


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