Re: [PATCH] mtd: spinand: cache the last read page to avoid redundant SPI operations

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

Hello,

On 07/09/2026 at 19:10:40 +08, fzz <1768315307@qq.com> wrote:

> When squashfs reads files through mtdblock, the mtdblock layer
> splits I/O into 512-byte sectors. For a 4K-page SPI NAND, this
> means reading the same page 8 times (4096 / 512), generating 7x
> redundant SPI read-from-cache operations. Each such operation
> involves a full SPI bus transaction, significantly slowing down
> boot time and file access.
>
> Cache the last successfully read page in spinand_device to avoid
> these redundant operations. When the same {target, eraseblock,
> page} is requested consecutively, the data is served directly
> from the bounce buffer (databuf) via memcpy, skipping the SPI
> transaction entirely.
>
> The cache is invalidated on write and erase operations. RAW reads,
> OOB reads, and continuous reads are excluded from caching to
> maintain correctness.

Why would you use mtdblock on top of a SPI NAND? It sounds like a very
bad choice.

Maybe mtdblock itself could be improved to avoid 512B accesses instead?

> Signed-off-by: fzz <1768315307@qq.com>

Unfortunately, for licensing and copyright reasons, pseudonyms are not
allowed in the Linux kernel.

> ---
>  drivers/mtd/nand/spi/core.c | 36 +++++++++++++++++++++++++++++++++++-
>  include/linux/mtd/spinand.h |  9 +++++++++
>  2 files changed, 44 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/mtd/nand/spi/core.c b/drivers/mtd/nand/spi/core.c
> index 8bf9301f25e7..fc082127bda8 100644
> --- a/drivers/mtd/nand/spi/core.c
> +++ b/drivers/mtd/nand/spi/core.c
> @@ -557,7 +557,14 @@ static int spinand_read_from_cache_op(struct spinand_device *spinand,
>  						    req->ooblen);
>  		else
>  			memcpy(req->oobbuf.in, spinand->oobbuf + req->ooboffs,
> -			       req->ooblen);
> +				req->ooblen);

Spurious change.

> +	}
> +

Thanks,
Miquèl