Re: [PATCH] mtd: spinand: Enable QE on all dies

[Miquel Raynal]

Hello Han,

On 07/08/2026 at 18:11:27 -05, han.xu@xxxxxxxxxxx wrote:

> From: Han Xu <han.xu@xxxxxxx>
>
> The QUAD ENABLE (QE) bit is stored in a per-die configuration
> register on some SPI-NAND devices. When a device contains multiple
> dies, updating the QE bit only on the currently selected die can
> leave the remaining dies operating in non-quad mode.
>  
> Iterate over all targets and update the QE setting on each die
> during initialization to ensure consistent quad I/O operation
> across the entire device.
>
> Tested on ISSI IS38SMW04G8B.
>
> Fixes: 7529df465248 ("mtd: nand: Add core infrastructure to support
> SPI NANDs")

There was no ISSI device back then, but I guess this can be useful for
other devices. However this shall be backported, so Cc: stable.

> Signed-off-by: Han Xu <han.xu@xxxxxxx>
> ---
>  drivers/mtd/nand/spi/core.c | 22 ++++++++++++++++++++--
>  1 file changed, 20 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/mtd/nand/spi/core.c b/drivers/mtd/nand/spi/core.c
> index 35365b67dd8e..744662533f37 100644
> --- a/drivers/mtd/nand/spi/core.c
> +++ b/drivers/mtd/nand/spi/core.c
> @@ -281,8 +281,26 @@ static int spinand_init_cfg_cache(struct spinand_device *spinand)
>  static int spinand_init_quad_enable(struct spinand_device *spinand,
>  				    bool enable)
>  {
> -	return spinand_upd_cfg(spinand, CFG_QUAD_ENABLE,
> -			       enable ? CFG_QUAD_ENABLE : 0);
> +	struct nand_device *nand = spinand_to_nand(spinand);
> +	unsigned int target;
> +	int ret;
> +
> +	/*
> +	 * QE is a per-die setting on some devices. Program each target
> +	 * individually when enabling or disabling quad I/O mode.
> +	 */
> +	for (target = 0; target < nand->memorg.ntargets; target++) {
> +		ret = spinand_select_target(spinand, target);
> +		if (ret)
> +			return ret;
> +
> +		ret = spinand_upd_cfg(spinand, CFG_QUAD_ENABLE,
> +				      enable ? CFG_QUAD_ENABLE : 0);
> +		if (ret)
> +			return ret;

If there is an issue in the middle of the loop, the chip will become
unusable. Perhaps we should reset the dies to the !QE state and return
an error to continue in degraded (single) mode if that happens?

Thanks,
Miquèl