[PATCH v3 4/5] cmd: mtd: fix speed measurement in the speed benchmark

[Heinrich Schuchardt]

On 10/10/25 14:04, Mikhail Kshevetskiy wrote:
> The shown speed is inversely proportional to the data size.
> See the output:
> 
>    spi-nand: spi_nand nand at 0: Micron SPI NAND was found.
>    spi-nand: spi_nand nand at 0: 256 MiB, block size: 128 KiB, page size: 2048, OOB size: 128
>    ...
>    => mtd read.benchmark spi-nand0 $loadaddr 0 0x40000
>    Reading 262144 byte(s) (128 page(s)) at offset 0x00000000
>    Read speed: 63kiB/s
>    => mtd read.benchmark spi-nand0 $loadaddr 0 0x20000
>    Reading 131072 byte(s) (64 page(s)) at offset 0x00000000
>    Read speed: 127kiB/s
>    => mtd read.benchmark spi-nand0 $loadaddr 0 0x10000
>    Reading 65536 byte(s) (32 page(s)) at offset 0x00000000
>    Read speed: 254kiB/s
> 
> In the spi-nand case 'io_op.len' is not always the same as 'len', thus
> we are using the wrong amount of data to derive the speed.
> 
> Also make sure we are using 64-bit calculation to get a more precise
> results.
> 
> Fixes: d246e70cf81d0 ("cmd: mtd: Enable speed benchmarking")
> Signed-off-by: Mikhail Kshevetskiy <mikhail.kshevetskiy at iopsys.eu>
> Reviewed-by: Miquel Raynal <miquel.raynal at bootlin.com>
> ---
>   cmd/mtd.c | 5 +++--
>   1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/cmd/mtd.c b/cmd/mtd.c
> index 689d8d11655..e415a2d7f02 100644
> --- a/cmd/mtd.c
> +++ b/cmd/mtd.c
> @@ -469,7 +469,7 @@ static int do_mtd_io(struct cmd_tbl *cmdtp, int flag, int argc,
>   		     char *const argv[])
>   {
>   	bool dump, read, raw, woob, benchmark, write_empty_pages, has_pages = false;
> -	u64 start_off, off, len, remaining, default_len;
> +	u64 start_off, off, len, remaining, default_len, speed;
>   	unsigned long bench_start, bench_end;
>   	struct mtd_oob_ops io_op = {};
>   	uint user_addr = 0, npages;
> @@ -595,9 +595,10 @@ static int do_mtd_io(struct cmd_tbl *cmdtp, int flag, int argc,
>   
>   	if (benchmark && bench_start) {
>   		bench_end = timer_get_us();
> +		speed = (len * 1000000) / (bench_end - bench_start);
>   		printf("%s speed: %lukiB/s\n",
>   		       read ? "Read" : "Write",
> -		       ((io_op.len * 1000000) / (bench_end - bench_start)) / 1024);
> +		       (unsigned long)(speed / 1024));

Some SoCs may not support 64bit divisions.
u64 lldiv(u64 dividend, u32 divisor) might be applicable here.
Please, have a look at include/div64.h.

Best regards

Heinrich


>   	}
>   
>   	led_activity_off();