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authorTomi Valkeinen <tomi.valkeinen@ti.com>2014-02-13 12:03:59 +0200
committerMike Turquette <mturquette@linaro.org>2014-02-26 18:23:46 -0800
commitb11d282dbea27db1788893115dfca8a7856bf205 (patch)
tree445a271a85312da38b01072699437cf05217252c /drivers/clk/clk-divider.c
parent1887c3a64fab8300a5be3fb5fd8d6474a63b50a0 (diff)
clk: divider: fix rate calculation for fractional rates
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 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 <tomi.valkeinen@ti.com> Signed-off-by: Mike Turquette <mturquette@linaro.org>
Diffstat (limited to 'drivers/clk/clk-divider.c')
-rw-r--r--drivers/clk/clk-divider.c10
1 files changed, 5 insertions, 5 deletions
diff --git a/drivers/clk/clk-divider.c b/drivers/clk/clk-divider.c
index 5543b7df8e16..ec22112e569f 100644
--- a/drivers/clk/clk-divider.c
+++ b/drivers/clk/clk-divider.c
@@ -24,7 +24,7 @@
* Traits of this clock:
* prepare - clk_prepare only ensures that parents are prepared
* enable - clk_enable only ensures that parents are enabled
- * rate - rate is adjustable. clk->rate = parent->rate / divisor
+ * rate - rate is adjustable. clk->rate = DIV_ROUND_UP(parent->rate / divisor)
* parent - fixed parent. No clk_set_parent support
*/
@@ -115,7 +115,7 @@ static unsigned long clk_divider_recalc_rate(struct clk_hw *hw,
return parent_rate;
}
- return parent_rate / div;
+ return DIV_ROUND_UP(parent_rate, div);
}
/*
@@ -185,7 +185,7 @@ static int 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;
@@ -207,7 +207,7 @@ static long clk_divider_round_rate(struct clk_hw *hw, unsigned long rate,
int div;
div = clk_divider_bestdiv(hw, rate, prate);
- return *prate / div;
+ return DIV_ROUND_UP(*prate, div);
}
static int clk_divider_set_rate(struct clk_hw *hw, unsigned long rate,
@@ -218,7 +218,7 @@ static int 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))