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| author | Tomi Valkeinen <tomi.valkeinen@ti.com> | 2014-02-13 12:04:00 +0200 |
|---|---|---|
| committer | Mike Turquette <mturquette@linaro.org> | 2014-02-26 18:23:58 -0800 |
| commit | 7e50e7e176634e8cc0335778915be75df41043dc (patch) | |
| tree | d89e206488b084af24d3336ed2ff42320e0b97c2 /drivers/clk/ti/divider.c | |
| parent | b11d282dbea27db1788893115dfca8a7856bf205 (diff) | |
| download | blackbird-op-linux-7e50e7e176634e8cc0335778915be75df41043dc.tar.gz blackbird-op-linux-7e50e7e176634e8cc0335778915be75df41043dc.zip | |
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 <tomi.valkeinen@ti.com>
Signed-off-by: Mike Turquette <mturquette@linaro.org>
Diffstat (limited to 'drivers/clk/ti/divider.c')
| -rw-r--r-- | drivers/clk/ti/divider.c | 8 |
1 files 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)) |
