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

[Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx>]

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().

>  	struct jedec_ecc_info *ecc;
>  	int jedec_version = 0;
>  	char id[5];
> @@ -40,25 +40,25 @@ 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;
> -	}
> -
>  	for (i = 0; i < JEDEC_PARAM_PAGES; i++) {
> -		ret = nand_read_data_op(chip, p, sizeof(*p), true);
> +		if (!i)
> +			ret = nand_read_param_page_op(chip, 0x40, &pbuf[i],
> +						      sizeof(*pbuf));
> +		else
> +			ret = nand_change_read_column_op(chip, sizeof(*pbuf) * i,
> +							 &pbuf[i], sizeof(*pbuf),
> +							 true);
>  		if (ret) {
>  			ret = 0;
>  			goto free_jedec_param_page;
>  		}
>  
> -		crc = onfi_crc16(ONFI_CRC_BASE, (u8 *)p, 510);
> -		if (crc == le16_to_cpu(p->crc))
> +		crc = onfi_crc16(ONFI_CRC_BASE, (u8 *)&pbuf[i], 510);
> +		if (crc == le16_to_cpu(pbuf[i].crc))
>  			break;
>  	}
>  
> @@ -67,6 +67,8 @@ int nand_jedec_detect(struct nand_chip *chip)
>  		goto free_jedec_param_page;
>  	}
>  
> +	p = pbuf;
> +
>  	/* Check version */
>  	val = le16_to_cpu(p->revision);
>  	if (val & (1 << 2))
> @@ -122,6 +124,6 @@ int nand_jedec_detect(struct nand_chip *chip)
>  	ret = 1;
>  
>  free_jedec_param_page:
> -	kfree(p);
> +	kfree(pbuf);
>  	return ret;
>  }


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