Re: [PATCH] mtd: rawnand: micron: Adapt the PAGE READ flow to constraint controllers

[Boris Brezillon <boris.brezillon@collabora.com>]

On Tue, 19 May 2020 09:46:39 +0200
Miquel Raynal <miquel.raynal@bootlin.com> wrote:

> There are controllers not able to just read data cycles on the
> bus. There are controllers not able to do a change column.
> 
> If we want to support both, we need to check which operation is
> supported first. This is the exact same mechanism that is in use for
> parameter page reads (ONFI/JEDEC) as the same problem occurs.
> 
> Speed testing does not show any throughput penalty so we do not
> optimize more than that. However it is likely that, in the future, a
> more robust and exhaustive test will run at boot time to avoid
> re-checking what is supported and what is not at every call.
> 
> Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>

This looks good to me, just one thing to address below and you can add

Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>

> ---
>  drivers/mtd/nand/raw/nand_micron.c | 44 ++++++++++++++++++++++++------
>  1 file changed, 35 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/mtd/nand/raw/nand_micron.c b/drivers/mtd/nand/raw/nand_micron.c
> index b2b047b245f4..bbd0ffbae19a 100644
> --- a/drivers/mtd/nand/raw/nand_micron.c
> +++ b/drivers/mtd/nand/raw/nand_micron.c
> @@ -192,6 +192,7 @@ static int micron_nand_on_die_ecc_status_4(struct nand_chip *chip, u8 status,
>  	struct micron_nand *micron = nand_get_manufacturer_data(chip);
>  	struct mtd_info *mtd = nand_to_mtd(chip);
>  	unsigned int step, max_bitflips = 0;
> +	bool use_datain = false;
>  	int ret;
>  
>  	if (!(status & NAND_ECC_STATUS_WRITE_RECOMMENDED)) {
> @@ -211,8 +212,18 @@ static int micron_nand_on_die_ecc_status_4(struct nand_chip *chip, u8 status,
>  	 * in non-raw mode, even if the user did not request those bytes.
>  	 */
>  	if (!oob_required) {
> -		ret = nand_read_data_op(chip, chip->oob_poi, mtd->oobsize,
> -					false, false);

Can we add a comment explaining what we're doing here (basically a
condensed version of the commit message).

> +		if (!nand_has_exec_op(chip) ||
> +		    !nand_read_data_op(chip, chip->oob_poi, mtd->oobsize, false,
> +				       true))
> +			use_datain = true;
> +
> +		if (use_datain)
> +			ret = nand_read_data_op(chip, chip->oob_poi,
> +						mtd->oobsize, false, false);
> +		else
> +			ret = nand_change_read_column_op(chip, mtd->writesize,
> +							 chip->oob_poi,
> +							 mtd->oobsize, false);
>  		if (ret)
>  			return ret;
>  	}
> @@ -285,6 +296,7 @@ micron_nand_read_page_on_die_ecc(struct nand_chip *chip, uint8_t *buf,
>  				 int oob_required, int page)
>  {
>  	struct mtd_info *mtd = nand_to_mtd(chip);
> +	bool use_datain = false;
>  	u8 status;
>  	int ret, max_bitflips = 0;
>  
> @@ -300,14 +312,28 @@ micron_nand_read_page_on_die_ecc(struct nand_chip *chip, uint8_t *buf,
>  	if (ret)
>  		goto out;
>  
> -	ret = nand_exit_status_op(chip);
> -	if (ret)
> -		goto out;

Same here.

> +	if (!nand_has_exec_op(chip) ||
> +	    !nand_read_data_op(chip, buf, mtd->writesize, false, true))
> +		use_datain = true;
>  
> -	ret = nand_read_data_op(chip, buf, mtd->writesize, false, false);
> -	if (!ret && oob_required)
> -		ret = nand_read_data_op(chip, chip->oob_poi, mtd->oobsize,
> -					false, false);
> +	if (use_datain) {
> +		ret = nand_exit_status_op(chip);
> +		if (ret)
> +			goto out;
> +
> +		ret = nand_read_data_op(chip, buf, mtd->writesize, false,
> +					false);
> +		if (!ret && oob_required)
> +			ret = nand_read_data_op(chip, chip->oob_poi,
> +						mtd->oobsize, false, false);
> +	} else {
> +		ret = nand_change_read_column_op(chip, 0, buf, mtd->writesize,
> +						 false);
> +		if (!ret && oob_required)
> +			ret = nand_change_read_column_op(chip, mtd->writesize,
> +							 chip->oob_poi,
> +							 mtd->oobsize, false);
> +	}
>  
>  	if (chip->ecc.strength == 4)
>  		max_bitflips = micron_nand_on_die_ecc_status_4(chip, status,


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