Re: [PATCH 1/5] mtd: rawnand: mtk: Correct low level time calculation of r/w cycle

[xiaolei li <xiaolei.li@xxxxxxxxxxxx>]

Hi Miquel,

Thanks for your review.


On Mon, 2019-04-29 at 11:03 +0200, Miquel Raynal wrote:
> Hi Xiaolei,
> 
> Xiaolei Li <xiaolei.li@xxxxxxxxxxxx> wrote on Mon, 29 Apr 2019 14:38:30
> +0800:
> 
> > At present, the flow of calculating AC timing of read/write cycle in SDR
> > mode is that:
> > At first, calculate high hold time which is valid for both read and write
> > cycle using the max value between tREH_min and tWH_min.
> > Secondly, calculate WE# pulse width using tWP_min.
> > Thridly, calculate RE# pulse width using the bigger one between tREA_max
> > and tRP_min.
> > 
> > But NAND SPEC shows that Controller should also meet write/read cycle time.
> > That is write cycle time should be more than tWC_min and read cycle should
> > be more than tRC_min. Obviously, we do not achieve that now.
> > 
> > This patch corrects the low level time calculation to meet minimum
> > read/write cycle time required. After getting the high hold time, WE# low
> > level time will be promised to meet tWP_min and tWC_min requirement,
> > and RE# low level time will be promised to meet tREA_max, tRP_min and
> > tRC_min requirement.
> > 
> > Fixes: 93db446a424c ("mtd: nand: move raw NAND related code to the raw/ subdir")
> 
> This is definitely not the faulty patch. Please use --follow when
> searching for the culprit, to avoid being blocked by the
> renaming/moving work.
Yes. This issue exists before raw/ sudir being created.

The faulty patch should be 'commit edfee3619c49 ("mtd: nand: mtk: add
->setup_data_interface() hook")' which cannot be found in git history
now.

Should I list it here?

> 
> Also a Cc: stable might be worth.
OK. Thanks.

> 
> > Signed-off-by: Xiaolei Li <xiaolei.li@xxxxxxxxxxxx>
> > ---
> >  drivers/mtd/nand/raw/mtk_nand.c | 14 +++++++++++---
> >  1 file changed, 11 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/mtd/nand/raw/mtk_nand.c b/drivers/mtd/nand/raw/mtk_nand.c
> > index b6b4602f5132..dd855f860a4b 100644
> > --- a/drivers/mtd/nand/raw/mtk_nand.c
> > +++ b/drivers/mtd/nand/raw/mtk_nand.c
> > @@ -508,7 +508,7 @@ 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, trlt;
> > +	u32 rate, tpoecs, tprecs, tc2r, tw2r, twh, twst = 0, trlt = 0;
> >  
> >  	timings = nand_get_sdr_timings(conf);
> >  	if (IS_ERR(timings))
> > @@ -544,11 +544,19 @@ static int mtk_nfc_setup_data_interface(struct nand_chip *chip, int csline,
> >  	twh = DIV_ROUND_UP(twh * rate, 1000000) - 1;
> >  	twh &= 0xf;
> >  
> > -	twst = timings->tWP_min / 1000;
> > +	/* Calculate min low level timing for write cycle */
> > +	if ((twh + 1) * 1000000 / rate < timings->tWC_min / 1000)
> > +		twst = (timings->tWC_min / 1000 - (twh + 1) * 1000000 / rate)
> > +			* 1000;
> > +	twst = max(timings->tWP_min, twst) / 1000;
> >  	twst = DIV_ROUND_UP(twst * rate, 1000000) - 1;
> >  	twst &= 0xf;
> >  
> > -	trlt = max(timings->tREA_max, timings->tRP_min) / 1000;
> > +	/* Calculate min low level timing for read cycle */
> > +	if ((twh + 1) * 1000000 / rate < timings->tRC_min / 1000)
> > +		trlt = (timings->tRC_min / 1000 - (twh + 1) * 1000000 / rate)
> > +			* 1000;
> > +	trlt = max3(trlt, timings->tREA_max, timings->tRP_min) / 1000;
> >  	trlt = DIV_ROUND_UP(trlt * rate, 1000000) - 1;
> >  	trlt &= 0xf;
> >  
> 
> 
> With this fixed,
> 
> Reviewed-by: Miquel Raynal <miquel.raynal@xxxxxxxxxxx>
> 
> Thanks,
> Miquèl

Thanks,
Xiaolei


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