Re: [PATCH v3 10/13] mtd: rawnand: jedec: Adapt the parameter page read to constraint controllers

[Miquel Raynal <miquel.raynal@bootlin.com>]

Boris Brezillon <boris.brezillon@collabora.com> wrote on Mon, 4 May
2020 10:51:44 +0200:

> On Mon,  4 May 2020 10:24:11 +0200
> Miquel Raynal <miquel.raynal@bootlin.com> 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.
> > 
> > Let's use a regular PARAMETER PAGE READ operation for the first
> > iteration and use eithe a CHANGE READ COLUMN or a simple DATA READ
> > operation for the following copies, depending on what the controller
> > supports. The default for non-exec-op compliant drivers remains
> > unchanged: use a SIMPLE READ.
> > 
> > Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
> > ---
> >  drivers/mtd/nand/raw/nand_jedec.c | 34 ++++++++++++++++++++-----------
> >  1 file changed, 22 insertions(+), 12 deletions(-)
> > 
> > diff --git a/drivers/mtd/nand/raw/nand_jedec.c b/drivers/mtd/nand/raw/nand_jedec.c
> > index 63069f1948a8..be270b36317e 100644
> > --- a/drivers/mtd/nand/raw/nand_jedec.c
> > +++ b/drivers/mtd/nand/raw/nand_jedec.c
> > @@ -25,8 +25,9 @@ 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;
> >  	struct jedec_ecc_info *ecc;
> > +	bool use_datain = false;
> >  	int jedec_version = 0;
> >  	char id[5];
> >  	int i, val, ret;
> > @@ -40,25 +41,32 @@ int nand_jedec_detect(struct nand_chip *chip)
> >  		return 0;
> >  
> >  	/* JEDEC chip: allocate a buffer to hold its parameter page */
> > -	p = kzalloc(sizeof(*p), GFP_KERNEL);
> > -	if (!p)
> > +	pbuf = kzalloc(sizeof(*pbuf) * JEDEC_PARAM_PAGES, GFP_KERNEL);
> > +	if (!pbuf)
> >  		return -ENOMEM;
> >  
> > -	ret = nand_read_param_page_op(chip, 0x40, NULL, 0);
> > -	if (ret) {
> > -		ret = 0;
> > -		goto free_jedec_param_page;
> > -	}
> > +	if (!nand_has_exec_op(chip) ||
> > +	    (nand_read_data_op(chip, &pbuf[0], sizeof(*pbuf), true, true) == 0))
> > +		use_datain = true;
> >  
> >  	for (i = 0; i < JEDEC_PARAM_PAGES; i++) {
> > -		ret = nand_read_data_op(chip, p, sizeof(*p), true, false);
> > +		if (!i)
> > +			ret = nand_read_param_page_op(chip, 0x40, &pbuf[i],
> > +						      sizeof(*pbuf));
> > +		else if (use_datain)
> > +			ret = nand_read_data_op(chip, &pbuf[i], sizeof(*pbuf),
> > +						true, false);
> > +		else
> > +			ret = nand_change_read_column_op(chip, sizeof(*pbuf) * i,
> > +							 &pbuf[i], sizeof(*pbuf),
> > +							 true);  
> 
> Now that you only ever read a page at a time, and given you don't do
> the majority_bit() thing when all pages are corrupted, I'd suggest
> sticking to one sizeof(*p) allocation and getting rid of the pbuf var.

Agreed, this is not truly necessary, but I am sure the majority_bit
calculation could definitely fit here so I was hoping it could get
added someday?
 
> 
> But it's not a big deal, so feel free to add
> 
> Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
> 
> if you don't want to send a new version.

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