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regulator: anatop: improve precision of delay time

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For cpufreq example, it takes 13 steps (25 mV for one step) to increase
vddcore from 0.95 V to 1.275 V, and the time of 64 clock cycles at
24 MHz for one step is ~2.67 uS, so the total delay time would be
~34.71 uS.  But the current calculation in the driver gives 39 uS.
Change the formula to have the addition of 1 be the last step, so that
we can get a more precise delay time.  For example above, the new
formula will give 35 uS.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
This commit is contained in:
Shawn Guo 2013-02-04 10:21:32 +08:00 committed by Mark Brown
parent 9ee417c074
commit ff1ce0571e
1 changed files with 2 additions and 2 deletions
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drivers/regulator/anatop-regulator.c
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@ -80,8 +80,8 @@ static int anatop_regmap_set_voltage_time_sel(struct regulator_dev *reg,
regmap_read(anatop_reg->anatop, anatop_reg->delay_reg, &val);
val = (val >> anatop_reg->delay_bit_shift) &
((1 << anatop_reg->delay_bit_width) - 1);
ret = (new_sel - old_sel) * ((LDO_RAMP_UP_UNIT_IN_CYCLES <<
val) / LDO_RAMP_UP_FREQ_IN_MHZ + 1);
ret = (new_sel - old_sel) * (LDO_RAMP_UP_UNIT_IN_CYCLES <<
val) / LDO_RAMP_UP_FREQ_IN_MHZ + 1;
}
return ret;