From 7e50e7e176634e8cc0335778915be75df41043dc Mon Sep 17 00:00:00 2001 From: Tomi Valkeinen Date: Thu, 13 Feb 2014 12:04:00 +0200 Subject: [PATCH] clk: ti/divider: fix rate calculation for fractional rates ti/clk-divider.c does not calculate the rates consistently at the moment. As an example, on OMAP3 we have a clock divider with a source clock of 864000000 Hz. With dividers 6, 7 and 8 the theoretical rates are: 6: 144000000 7: 123428571.428571... 8: 108000000 Calling clk_round_rate() with the rate in the first column will give the rate in the second column: 144000000 -> 144000000 143999999 -> 123428571 123428572 -> 123428571 123428571 -> 108000000 Note how clk_round_rate() returns 123428571 for rates from 123428572 to 143999999, which is mathematically correct, but when clk_round_rate() is called with 123428571, the returned value is surprisingly 108000000. This means that the following code works a bit oddly: rate = clk_round_rate(clk, 123428572); clk_set_rate(clk, rate); As clk_set_rate() also does clock rate rounding, the result is that the clock is set to the rate of 108000000, not 123428571 returned by the clk_round_rate. This patch changes the ti/clk-divider.c to use DIV_ROUND_UP when calculating the rate. This gives the following behavior which fixes the inconsistency: 144000000 -> 144000000 143999999 -> 123428572 123428572 -> 123428572 123428571 -> 108000000 Signed-off-by: Tomi Valkeinen Signed-off-by: Mike Turquette --- drivers/clk/ti/divider.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/drivers/clk/ti/divider.c b/drivers/clk/ti/divider.c index a15e445570b2..e6aa10db7bba 100644 --- a/drivers/clk/ti/divider.c +++ b/drivers/clk/ti/divider.c @@ -112,7 +112,7 @@ static unsigned long ti_clk_divider_recalc_rate(struct clk_hw *hw, return parent_rate; } - return parent_rate / div; + return DIV_ROUND_UP(parent_rate, div); } /* @@ -182,7 +182,7 @@ static int ti_clk_divider_bestdiv(struct clk_hw *hw, unsigned long rate, } parent_rate = __clk_round_rate(__clk_get_parent(hw->clk), MULT_ROUND_UP(rate, i)); - now = parent_rate / i; + now = DIV_ROUND_UP(parent_rate, i); if (now <= rate && now > best) { bestdiv = i; best = now; @@ -205,7 +205,7 @@ static long ti_clk_divider_round_rate(struct clk_hw *hw, unsigned long rate, int div; div = ti_clk_divider_bestdiv(hw, rate, prate); - return *prate / div; + return DIV_ROUND_UP(*prate, div); } static int ti_clk_divider_set_rate(struct clk_hw *hw, unsigned long rate, @@ -216,7 +216,7 @@ static int ti_clk_divider_set_rate(struct clk_hw *hw, unsigned long rate, unsigned long flags = 0; u32 val; - div = parent_rate / rate; + div = DIV_ROUND_UP(parent_rate, rate); value = _get_val(divider, div); if (value > div_mask(divider)) -- 2.11.0