2018-04-18 09:35:33

by Luca Ellero

Subject: [PATCH] mtd: dataflash: replace msleep with usleep_range

Since msleep is based on jiffies, this 3 ms sleep becomes actually 20 ms.
Worst of all, since this sleep is used in a loop when writing, a single page
write (256 to 1024 bytes) causes 17 ms extra time.
When writing large files (for example u-boot is usually 512 KB) this delay
adds up to minutes.
See Documentation/timers/timers-howto.txt "Why not msleep for (1ms - 20ms)".

Signed-off-by: Luca Ellero <[email protected]>
---
drivers/mtd/devices/mtd_dataflash.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/mtd/devices/mtd_dataflash.c b/drivers/mtd/devices/mtd_dataflash.c
index aaaeaae..3a6f450 100644
--- a/drivers/mtd/devices/mtd_dataflash.c
+++ b/drivers/mtd/devices/mtd_dataflash.c
@@ -140,7 +140,7 @@ static int dataflash_waitready(struct spi_device *spi)
if (status & (1 << 7)) /* RDY/nBSY */
return status;

- msleep(3);
+ usleep_range(3000, 4000);
}
}

--
2.7.4

2018-04-26 18:06:36

by Boris Brezillon

Subject: Re: [PATCH] mtd: dataflash: replace msleep with usleep_range

On Wed, 18 Apr 2018 11:26:26 +0200
Luca Ellero <[email protected]> wrote:

> Since msleep is based on jiffies, this 3 ms sleep becomes actually 20 ms.
> Worst of all, since this sleep is used in a loop when writing, a single page
> write (256 to 1024 bytes) causes 17 ms extra time.
> When writing large files (for example u-boot is usually 512 KB) this delay
> adds up to minutes.
> See Documentation/timers/timers-howto.txt "Why not msleep for (1ms - 20ms)".
>
> Signed-off-by: Luca Ellero <[email protected]>

Applied.

Thanks,

Boris

> ---
> drivers/mtd/devices/mtd_dataflash.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/mtd/devices/mtd_dataflash.c b/drivers/mtd/devices/mtd_dataflash.c
> index aaaeaae..3a6f450 100644
> --- a/drivers/mtd/devices/mtd_dataflash.c
> +++ b/drivers/mtd/devices/mtd_dataflash.c
> @@ -140,7 +140,7 @@ static int dataflash_waitready(struct spi_device *spi)
> if (status & (1 << 7)) /* RDY/nBSY */
> return status;
>
> - msleep(3);
> + usleep_range(3000, 4000);
> }
> }
>