diff options
| -rw-r--r-- | drivers/clk/rockchip/clk-mmc-phase.c | 45 |
1 files changed, 30 insertions, 15 deletions
diff --git a/drivers/clk/rockchip/clk-mmc-phase.c b/drivers/clk/rockchip/clk-mmc-phase.c index 9b613426e968..a797d8625f6d 100644 --- a/drivers/clk/rockchip/clk-mmc-phase.c +++ b/drivers/clk/rockchip/clk-mmc-phase.c @@ -45,8 +45,8 @@ static unsigned long rockchip_mmc_recalc(struct clk_hw *hw, #define PSECS_PER_SEC 1000000000000LL /* - * Each fine delay is between 40ps-80ps. Assume each fine delay is 60ps to - * simplify calculations. So 45degs could be anywhere between 33deg and 66deg. + * Each fine delay is between 44ps-77ps. Assume each fine delay is 60ps to + * simplify calculations. So 45degs could be anywhere between 33deg and 57.8deg. */ #define ROCKCHIP_MMC_DELAY_ELEMENT_PSEC 60 @@ -84,22 +84,37 @@ static int rockchip_mmc_set_phase(struct clk_hw *hw, int degrees) u32 raw_value; u64 delay; - /* allow 22 to be 22.5 */ - degrees++; - /* floor to 22.5 increment */ - degrees -= ((degrees) * 10 % 225) / 10; - nineties = degrees / 90; - /* 22.5 multiples */ - remainder = (degrees % 90) / 22; - + remainder = (degrees % 90); + + /* + * Due to the inexact nature of the "fine" delay, we might + * actually go non-monotonic. We don't go _too_ monotonic + * though, so we should be OK. Here are options of how we may + * work: + * + * Ideally we end up with: + * 1.0, 2.0, ..., 69.0, 70.0, ..., 89.0, 90.0 + * + * On one extreme (if delay is actually 44ps): + * .73, 1.5, ..., 50.6, 51.3, ..., 65.3, 90.0 + * The other (if delay is actually 77ps): + * 1.3, 2.6, ..., 88.6. 89.8, ..., 114.0, 90 + * + * It's possible we might make a delay that is up to 25 + * degrees off from what we think we're making. That's OK + * though because we should be REALLY far from any bad range. + */ + + /* + * Convert to delay; do a little extra work to make sure we + * don't overflow 32-bit / 64-bit numbers. + */ delay = PSECS_PER_SEC; - do_div(delay, rate); - /* / 360 / 22.5 */ - do_div(delay, 16); - do_div(delay, ROCKCHIP_MMC_DELAY_ELEMENT_PSEC); - delay *= remainder; + do_div(delay, 10000); + do_div(delay, (rate / 1000) * 36 * ROCKCHIP_MMC_DELAY_ELEMENT_PSEC); + delay_num = (u8) min(delay, 255ULL); raw_value = delay_num ? ROCKCHIP_MMC_DELAY_SEL : 0; |