Subject: [PATCH v2 2/8] clk: rockchip: Make calculations use rounding

From: [email-masked] (Michael Turquette)
Date: Thu, 22 Oct 2015 05:04:00 -0700

Quoting Heiko Stuebner (2015-09-30 07:07:38)
> From: Douglas Anderson <[email-masked]>
> 
> Let's use DIV_ROUND_CLOSEST for rounding, not just truncating
> division.  This lets us get closer to the right rate.
> 
> Before this:
>   set_phase(86) delay_nums=26 reg[0xf000420c]=0x468 actual_degrees=83
>   set_phase(89) delay_nums=27 reg[0xf000420c]=0x46c actual_degrees=86
> 
> After this:
>   set_phase(86) delay_nums=27 reg[0xf000420c]=0x46c actual_degrees=86
>   set_phase(89) delay_nums=28 reg[0xf000420c]=0x470 actual_degrees=90
> 
> Signed-off-by: Douglas Anderson <[email-masked]>
> Signed-off-by: Heiko Stuebner <[email-masked]>

Looks good to me. What tree do you want this to go through?

Regards,
Mike

> ---
>  drivers/clk/rockchip/clk-mmc-phase.c | 13 +++++++------
>  1 file changed, 7 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/clk/rockchip/clk-mmc-phase.c b/drivers/clk/rockchip/clk-mmc-phase.c
> index a797d86..bc24e5a 100644
> --- a/drivers/clk/rockchip/clk-mmc-phase.c
> +++ b/drivers/clk/rockchip/clk-mmc-phase.c
> @@ -69,7 +69,7 @@ static int rockchip_mmc_get_phase(struct clk_hw *hw)
>  
>                 delay_num = (raw_value & ROCKCHIP_MMC_DELAYNUM_MASK);
>                 delay_num >>= ROCKCHIP_MMC_DELAYNUM_OFFSET;
> -               degrees += delay_num * factor / 10000;
> +               degrees += DIV_ROUND_CLOSEST(delay_num * factor, 10000);
>         }
>  
>         return degrees % 360;
> @@ -82,7 +82,7 @@ static int rockchip_mmc_set_phase(struct clk_hw *hw, int degrees)
>         u8 nineties, remainder;
>         u8 delay_num;
>         u32 raw_value;
> -       u64 delay;
> +       u32 delay;
>  
>         nineties = degrees / 90;
>         remainder = (degrees % 90);
> @@ -110,12 +110,13 @@ static int rockchip_mmc_set_phase(struct clk_hw *hw, int degrees)
>          * Convert to delay; do a little extra work to make sure we
>          * don't overflow 32-bit / 64-bit numbers.
>          */
> -       delay = PSECS_PER_SEC;
> +       delay = 10000000; /* PSECS_PER_SEC / 10000 / 10 */
>         delay *= remainder;
> -       do_div(delay, 10000);
> -       do_div(delay, (rate / 1000) * 36 * ROCKCHIP_MMC_DELAY_ELEMENT_PSEC);
> +       delay = DIV_ROUND_CLOSEST(delay,
> +                       (rate / 1000) * 36 *
> +                               (ROCKCHIP_MMC_DELAY_ELEMENT_PSEC / 10));
>  
> -       delay_num = (u8) min(delay, 255ULL);
> +       delay_num = (u8) min_t(u32, delay, 255);
>  
>         raw_value = delay_num ? ROCKCHIP_MMC_DELAY_SEL : 0;
>         raw_value |= delay_num << ROCKCHIP_MMC_DELAYNUM_OFFSET;
> -- 
> 2.5.1
>