Re: [PATCH v2 08/11] mtd: rawnand: jedec: Adapt the parameter page read to constraint controllers

[Miquel Raynal <miquel.raynal@xxxxxxxxxxx>]

Hi Boris,

Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx> wrote on Wed, 29 Apr
2020 18:04:05 +0200:

> On Wed, 29 Apr 2020 17:55:37 +0200
> Miquel Raynal <miquel.raynal@xxxxxxxxxxx> wrote:
> 
> > We already know that there are controllers not able to read the three
> > copies of the parameter page in one go. The workaround was to first
> > request the controller to assert command and address cycles on the
> > NAND bus to trigger a parameter page read, and then do a read
> > operation for each page.
> > 
> > But there are also controllers which are not able to split the
> > parameter page read between the command/address cycles and the actual
> > data operation.
> > 
> > All controllers are expected to be able to change the read column
> > though. So let's use a regular parameter page read operation for the
> > first iteration and use a change read column operation for the
> > following copies.
> > 
> > The extra command and address cycles sent over the NAND bus are
> > negligible compared to the amount of data that is being transferred
> > anyway.
> > 
> > Signed-off-by: Miquel Raynal <miquel.raynal@xxxxxxxxxxx>
> > ---
> >  drivers/mtd/nand/raw/nand_jedec.c | 28 +++++++++++++++-------------
> >  1 file changed, 15 insertions(+), 13 deletions(-)
> > 
> > diff --git a/drivers/mtd/nand/raw/nand_jedec.c b/drivers/mtd/nand/raw/nand_jedec.c
> > index 15937e02c64f..b2be9056759a 100644
> > --- a/drivers/mtd/nand/raw/nand_jedec.c
> > +++ b/drivers/mtd/nand/raw/nand_jedec.c
> > @@ -25,7 +25,7 @@ int nand_jedec_detect(struct nand_chip *chip)
> >  {
> >  	struct mtd_info *mtd = nand_to_mtd(chip);
> >  	struct nand_memory_organization *memorg;
> > -	struct nand_jedec_params *p;
> > +	struct nand_jedec_params *p = NULL, *pbuf;  
> 
> Looks like you've merged 2 different commits here. I remember you had a
> separate commit adding pbuf to avoid an extra memcpy().

Actually this was only fixed in the onfi detection routine. The jedec
equivalent does not copy the page (the copy came from the 3-way merge
that has only been added to onfi detection).

Here pbuf represents the buffer containing the three pages while p now
only points to the actual page that is correct.

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