Re: [PATCH] pxa3xx_nand: fix time calculation

[Artem Bityutskiy <dedekind1@gmail.com>]

On Wed, 2009-10-07 at 11:31 +0200, Enrico Scholz wrote:
> Use DIV_ROUND_UP to calculate number of clocks.  Else, calculated clocks
> are nearly always to low and for times < 10ns, they will be negative on
> PXA320  (which has a nand clock of 104 MHz).
> 
> Signed-off-by: Enrico Scholz <enrico.scholz@sigma-chemnitz.de>
> ---
>  drivers/mtd/nand/pxa3xx_nand.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/mtd/nand/pxa3xx_nand.c b/drivers/mtd/nand/pxa3xx_nand.c
> index 6ea520a..32cb4d1 100644
> --- a/drivers/mtd/nand/pxa3xx_nand.c
> +++ b/drivers/mtd/nand/pxa3xx_nand.c
> @@ -316,7 +316,7 @@ static struct pxa3xx_nand_flash *builtin_flash_types[] = {
>  #define tAR_NDTR1(r)	(((r) >> 0) & 0xf)
>  
>  /* convert nano-seconds to nand flash controller clock cycles */
> -#define ns2cycle(ns, clk)	(int)(((ns) * (clk / 1000000) / 1000) - 1)
> +#define ns2cycle(ns, clk)	(int)(DIV_ROUND_UP((ns) * (clk / 1000000), 1000) - 1)

Why there is -1 at the end?

-- 
Best Regards,
Artem Bityutskiy (Артём Битюцкий)