[PATCH 04/19] clk: at91: sam9x60-pll: use frac when computing pll frequency

Claudiu Beznea
2020-07-15T11:24:53Z

According to datasheet the PLL frequency is computed using the following
formula: parent_rate * (mul + 1 + frac/2^22)/(div + 1). Use this
formula.

Fixes: a436c2a447e59 ("clk: at91: add sam9x60 PLL driver")
Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
---
drivers/clk/at91/clk-sam9x60-pll.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/clk/at91/clk-sam9x60-pll.c b/drivers/clk/at91/clk-sam9x60-pll.c
index 3522eae2edd6..d3152c0afcbf 100644
--- a/drivers/clk/at91/clk-sam9x60-pll.c
+++ b/drivers/clk/at91/clk-sam9x60-pll.c
@@ -152,7 +152,8 @@ static unsigned long sam9x60_pll_recalc_rate(struct clk_hw *hw,
{
struct sam9x60_pll *pll = to_sam9x60_pll(hw);

- return (parent_rate * (pll->mul + 1)) / (pll->div + 1);
+ return DIV_ROUND_CLOSEST_ULL((parent_rate * (pll->mul + 1) +
+ ((u64)parent_rate * pll->frac >> 22)), (pll->div + 1));
}

static long sam9x60_pll_get_best_div_mul(struct sam9x60_pll *pll,
--
2.7.4