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

From: Heiko Stuebner
Date: Mon Aug 31 2015 - 14:24:34 EST


From: Douglas Anderson <dianders@xxxxxxxxxxxx>

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 <dianders@xxxxxxxxxxxx>
Signed-off-by: Heiko Stuebner <heiko@xxxxxxxxx>
---
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;
--
2.1.4

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/