Re: [PATCH v2 05/15] mtd: nand: add manufacturer specific initialization/detection steps

[Boris Brezillon <boris.brezillon@free-electrons.com>]

On Sat, 18 Jun 2016 11:23:01 +0200
Richard Weinberger <richard@nod.at> wrote:

> Boris,
> 
> Am 08.06.2016 um 15:00 schrieb Boris Brezillon:
> > A lot of NANDs are implementing generic features in a non-generic way,
> > or are providing advanced auto-detection logic where the NAND ID bytes
> > meaning changes with the NAND generation.
> > 
> > Providing this vendor specific initialization step will allow us to get
> > rid of the full ids in the nand_ids table or all the vendor specific
> > cases added over the time in the generic NAND ID decoding logic.
> > 
> > Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
> > ---
> >  drivers/mtd/nand/nand_base.c | 42 ++++++++++++++++++++++++++++++++----------
> >  include/linux/mtd/nand.h     | 36 ++++++++++++++++++++++++++++++++++++
> >  2 files changed, 68 insertions(+), 10 deletions(-)
> > 
> > diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
> > index 95e9a8e..0a7d1c6 100644
> > --- a/drivers/mtd/nand/nand_base.c
> > +++ b/drivers/mtd/nand/nand_base.c
> > @@ -3580,7 +3580,7 @@ static int nand_get_bits_per_cell(u8 cellinfo)
> >   * chip. The rest of the parameters must be decoded according to generic or
> >   * manufacturer-specific "extended ID" decoding patterns.
> >   */
> > -static void nand_decode_ext_id(struct nand_chip *chip)
> > +void nand_decode_ext_id(struct nand_chip *chip)
> >  {
> >  	struct mtd_info *mtd = nand_to_mtd(chip);
> >  	int extid, id_len = chip->id.len;
> > @@ -3705,6 +3705,7 @@ static void nand_decode_ext_id(struct nand_chip *chip)
> >  
> >  	}
> >  }
> > +EXPORT_SYMBOL_GPL(nand_decode_ext_id);
> >  
> >  /*
> >   * Old devices have chip data hardcoded in the device ID table. nand_decode_id
> > @@ -3815,7 +3816,7 @@ static int nand_detect(struct nand_chip *chip, struct nand_flash_dev *type)
> >  {
> >  	struct mtd_info *mtd = nand_to_mtd(chip);
> >  	int busw;
> > -	int i, maf_idx;
> > +	int i, maf_idx, ret;
> >  	u8 *id_data = chip->id.data;
> >  	u8 maf_id, dev_id;
> >  
> > @@ -3856,6 +3857,14 @@ static int nand_detect(struct nand_chip *chip, struct nand_flash_dev *type)
> >  
> >  	chip->id.len = nand_id_len(id_data, 8);
> >  
> > +	/* Try to identify manufacturer */
> > +	for (maf_idx = 0; nand_manuf_ids[maf_idx].id != 0x0; maf_idx++) {
> > +		if (nand_manuf_ids[maf_idx].id == maf_id)
> > +			break;
> > +	}
> > +
> > +	chip->manufacturer.ops = nand_manuf_ids[maf_idx].ops;
> > +  
> 
> Instead of checking on every access whether chip->manufacturer.ops is present, just
> assign a nop field.
> i.e.
> 
> diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
> index 55f3ab8..aadebe7 100644
> --- a/drivers/mtd/nand/nand_base.c
> +++ b/drivers/mtd/nand/nand_base.c
> @@ -3703,6 +3703,10 @@ static int nand_detect(struct nand_chip *chip, struct nand_flash_dev *type)
> 
>  	chip->manufacturer.ops = nand_manuf_ids[maf_idx].ops;
> 
> +	if (!chip->manufacturer.ops)
> +		/* assign no operations */
> +		chip->manufacturer.ops = nand_manuf_ids[0].ops;
> +
>  	if (!type)
>  		type = nand_flash_ids;
> 
> diff --git a/drivers/mtd/nand/nand_ids.c b/drivers/mtd/nand/nand_ids.c
> index f1476ff..cdd26af 100644
> --- a/drivers/mtd/nand/nand_ids.c
> +++ b/drivers/mtd/nand/nand_ids.c
> @@ -173,6 +173,8 @@ extern const struct nand_manufacturer_ops micron_nand_manuf_ops;
>  extern const struct nand_manufacturer_ops amd_nand_manuf_ops;
>  extern const struct nand_manufacturer_ops macronix_nand_manuf_ops;
> 
> +static const struct nand_manufacturer_ops no_ops;
> +
>  struct nand_manufacturers nand_manuf_ids[] = {
>  	{NAND_MFR_TOSHIBA, "Toshiba", &toshiba_nand_manuf_ops},
>  	{NAND_MFR_SAMSUNG, "Samsung", &samsung_nand_manuf_ops},
> @@ -188,7 +190,7 @@ struct nand_manufacturers nand_manuf_ids[] = {
>  	{NAND_MFR_SANDISK, "SanDisk"},
>  	{NAND_MFR_INTEL, "Intel"},
>  	{NAND_MFR_ATO, "ATO"},
> -	{0x0, "Unknown"}
> +	{0x0, "Unknown", &no_ops}
>  };
> 
>  EXPORT_SYMBOL(nand_manuf_ids);
> 

Sorry, but I don't see any added value in adding this no_ops instance.
The NULL value is supposed to represent no_ops.
That's not like this path was critical: it's only call once during NAND
initialization.


How about adding the following helpers instead:

static inline bool nand_has_manufacturer_ops(struct nand_chip * chip)
{
	return chip->manufacturer.ops != NULL;
}

static inline void nand_manufacturer_detect(struct nand_chip * chip)
{
	if (!chip->manufacturer.ops || chip->manufacturer.ops->detect)
		return;

	chip->manufacturer.ops->detect(chip);
}

static inline int nand_manufacturer_init(struct nand_chip * chip)
{
	if (!chip->manufacturer.ops || chip->manufacturer.ops->init)
		return 0;

	return chip->manufacturer.ops->init(chip);
}

> 
> >  	if (!type)
> >  		type = nand_flash_ids;
> >  
> > @@ -3903,8 +3912,14 @@ static int nand_detect(struct nand_chip *chip, struct nand_flash_dev *type)
> >  	chip->chipsize = (uint64_t)type->chipsize << 20;
> >  
> >  	if (!type->pagesize) {
> > -		/* Decode parameters from extended ID */
> > -		nand_decode_ext_id(chip);
> > +		/*
> > +		 * Try manufacturer detection if available and use
> > +		 * nand_decode_ext_id() otherwise.
> > +		 */
> > +		if (chip->manufacturer.ops->detect)  
> 
> You need to check here for chip->manufacturer.ops first.

Correct.