linux-kernel - Re: [PATCH] mtd: dataflash: replace msleep with usleep

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Date:   Thu, 26 Apr 2018 20:03:48 +0200
From:   Boris Brezillon <boris.brezillon@...tlin.com>
To:     Luca Ellero <luca.ellero@...ckedbrain.com>
Cc:     Marek Vasut <marek.vasut@...il.com>,
        Andrey Smirnov <andrew.smirnov@...il.com>,
        Richard Weinberger <richard@....at>,
        linux-kernel@...r.kernel.org, linux-mtd@...ts.infradead.org,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Brian Norris <computersforpeace@...il.com>,
        David Woodhouse <dwmw2@...radead.org>
Subject: Re: [PATCH] mtd: dataflash: replace msleep with usleep_range

On Wed, 18 Apr 2018 11:26:26 +0200
Luca Ellero <luca.ellero@...ckedbrain.com> 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 <luca.ellero@...ckedbrain.com>

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);
>  	}
>  }
>