Re: [PATCH v2 2/5] mtd: rawnand: mtk: Improve data sampling timing for read cycle

[xiaolei li <xiaolei.li@mediatek.com>]

On Tue, 2019-04-30 at 14:11 +0200, Miquel Raynal wrote:
> Hi Xiaolei,
> 
> Xiaolei Li <xiaolei.li@mediatek.com> wrote on Tue, 30 Apr 2019 18:02:47
> +0800:
> 
> > Currently, we expand RE# low level time by choosing the max value
> > between RE# pulse width and RE# access time, and sample data at the
> > rising edge of RE#.
> > 
> > Then, if RE# access time is bigger than RE# pulse width, the real
> > read cycle time may be more than NAND SPEC required. This makes
> > read performance be worse than that expected.
> > 
> > This patch improves data sampling timing by calculating RE# low level
> > time according to RE# pulse width. If RE# access time is bigger than
> > RE# pulse width, then delay sampling data timing.
> > 
> > The result of contrast test base on MT2712 evaluat board is as follow.
> > 
> > nand: Micron MT29F16G08ADBCAH4
> > nand: 2048 MiB, SLC, erase size: 256 KiB, page size: 4096, OOB size: 224
> > NFI 2x clock rate: 124800000 HZ.
> > 
> > Read speed without this patch:
> > mtd_speedtest: page read speed is 14012 KiB/s
> > mtd_speedtest: 2 page read speed is 14860 KiB/s
> > 
> > Read speed with this patch:
> > mtd_speedtest: page read speed is 18724 KiB/s
> > mtd_speedtest: 2 page read speed is 18713 KiB/s
> > 
> > Signed-off-by: Xiaolei Li <xiaolei.li@mediatek.com>
> > ---
> >  drivers/mtd/nand/raw/mtk_nand.c | 46 ++++++++++++++++++++++++++-------
> >  1 file changed, 36 insertions(+), 10 deletions(-)
> > 
> > diff --git a/drivers/mtd/nand/raw/mtk_nand.c b/drivers/mtd/nand/raw/mtk_nand.c
> > index 4fbb0c6ecae3..e90c38c6f835 100644
> > --- a/drivers/mtd/nand/raw/mtk_nand.c
> > +++ b/drivers/mtd/nand/raw/mtk_nand.c
> > @@ -87,6 +87,10 @@
> >  #define NFI_FDMM(x)		(0xA4 + (x) * sizeof(u32) * 2)
> >  #define NFI_FDM_MAX_SIZE	(8)
> >  #define NFI_FDM_MIN_SIZE	(1)
> > +#define NFI_DEBUG_CON1		(0x220)
> > +#define		STROBE_MASK		GENMASK(4, 3)
> > +#define		STROBE_SHIFT		(3)
> > +#define		MAX_STROBE_DLY		(3)
> >  #define NFI_MASTER_STA		(0x224)
> >  #define		MASTER_STA_MASK		(0x0FFF)
> >  #define NFI_EMPTY_THRESH	(0x23C)
> > @@ -509,7 +513,7 @@ static int mtk_nfc_setup_data_interface(struct nand_chip *chip, int csline,
> >  	struct mtk_nfc *nfc = nand_get_controller_data(chip);
> >  	const struct nand_sdr_timings *timings;
> >  	u32 rate, tpoecs, tprecs, tc2r, tw2r, twh, twst = 0, trlt = 0;
> > -	u32 thold;
> > +	u32 temp, tsel = 0;
> >  
> >  	timings = nand_get_sdr_timings(conf);
> >  	if (IS_ERR(timings))
> > @@ -546,30 +550,52 @@ static int mtk_nfc_setup_data_interface(struct nand_chip *chip, int csline,
> >  	twh &= 0xf;
> >  
> >  	/* Calculate real WE#/RE# hold time in nanosecond */
> > -	thold = (twh + 1) * 1000000 / rate;
> > +	temp = (twh + 1) * 1000000 / rate;
> >  	/* nanosecond to picosecond */
> > -	thold *= 1000;
> > +	temp *= 1000;
> >  
> >  	/**
> >  	 * WE# low level time should be expaned to meet WE# pulse time
> >  	 * and WE# cycle time at the same time.
> >  	 */
> > -	if (thold < timings->tWC_min)
> > -		twst = timings->tWC_min - thold;
> > +	if (temp < timings->tWC_min)
> > +		twst = timings->tWC_min - temp;
> >  	twst = max(timings->tWP_min, twst) / 1000;
> >  	twst = DIV_ROUND_UP(twst * rate, 1000000) - 1;
> >  	twst &= 0xf;
> >  
> >  	/**
> > -	 * RE# low level time should be expaned to meet RE# pulse time,
> > -	 * RE# access time and RE# cycle time at the same time.
> > +	 * RE# low level time should be expaned to meet RE# pulse time
> > +	 * and RE# cycle time at the same time.
> >  	 */
> > -	if (thold < timings->tRC_min)
> > -		trlt = timings->tRC_min - thold;
> > -	trlt = max3(trlt, timings->tREA_max, timings->tRP_min) / 1000;
> > +	if (temp < timings->tRC_min)
> > +		trlt = timings->tRC_min - temp;
> > +	trlt = max(trlt, timings->tRP_min) / 1000;
> >  	trlt = DIV_ROUND_UP(trlt * rate, 1000000) - 1;
> >  	trlt &= 0xf;
> >  
> > +	/**
> 
>         /*
> 
> > +	 * Calculate strobe select timing.
> > +	 * If RE# access time is bigger than RE# pulse time,
> > +	 * delay sampling data timing.
> > +	 */
> > +	temp = (trlt + 1) * 1000000 / rate;
> 
> You could precise what unit conversion you do here.
OK. Unit here is nanosecond. I will describe it in next patch version.

> 
> > +	/* nanosecond to picosecond */
> > +	temp *= 1000;
> > +	if (temp < timings->tREA_max) {
> > +		tsel = timings->tREA_max / 1000;
> > +		tsel = DIV_ROUND_UP(tsel * rate, 1000000);
> > +		tsel -= (trlt + 1);
> > +		if (tsel > MAX_STROBE_DLY) {
> > +			trlt += tsel - MAX_STROBE_DLY;
> > +			tsel = MAX_STROBE_DLY;
> > +		}
> > +	}
> > +	temp = nfi_readl(nfc, NFI_DEBUG_CON1);
> > +	temp &= ~STROBE_MASK;
> > +	temp |= tsel << STROBE_SHIFT;
> > +	nfi_writel(nfc, temp, NFI_DEBUG_CON1);
> > +
> >  	/*
> >  	 * ACCON: access timing control register
> >  	 * -------------------------------------
> 
> With this:
> 
> Reviewed-by: Miquel Raynal <miquel.raynal@bootlin.com>
> 
> 
> Thanks,
> Miquèl

Thanks,
Xiaolei



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