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pwm: optimizing pwm duty calculation

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PD#165143: pwm: optimizing pwm duty calculation

1.Fix duty equal 0% and 100% duty count incorrect
2.Change period unit to ps to increase accuracy

Change-Id: Ied478f21ac4b4f9f3d1508d69dfbcdbb9ca4e732
Signed-off-by: Jian Hu <jian.hu@amlogic.com>
This commit is contained in:
Jian Hu
2018-04-27 17:16:44 +08:00
committed by Yixun Lan
parent 7ed184dc94
commit 16a0d05225
1 changed files with 12 additions and 8 deletions
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20
drivers/amlogic/pwm/pwm_meson.c
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@@ -164,7 +164,8 @@ static int meson_pwm_calc(struct meson_pwm *meson,
unsigned int duty, unsigned int period)
{
unsigned int pre_div, cnt, duty_cnt;
unsigned long fin_freq = -1, fin_ns;
unsigned long fin_freq = -1;
u64 fin_ps;
if (~(meson->inverter_mask >> id) & 0x1)
duty = period - duty;
@@ -180,13 +181,15 @@ static int meson_pwm_calc(struct meson_pwm *meson,
}
dev_dbg(meson->chip.dev, "fin_freq: %lu Hz\n", fin_freq);
fin_ns = NSEC_PER_SEC / fin_freq;
fin_ps = (u64)NSEC_PER_SEC * 1000;
do_div(fin_ps, fin_freq);
/* Calc pre_div with the period */
for (pre_div = 0; pre_div < MISC_CLK_DIV_MASK; pre_div++) {
cnt = DIV_ROUND_CLOSEST(period, fin_ns * (pre_div + 1));
dev_dbg(meson->chip.dev, "fin_ns=%lu pre_div=%u cnt=%u\n",
fin_ns, pre_div, cnt);
cnt = DIV_ROUND_CLOSEST_ULL((u64)period * 1000,
fin_ps * (pre_div + 1));
dev_dbg(meson->chip.dev, "fin_ns=%llu pre_div=%u cnt=%u\n",
fin_ps, pre_div, cnt);
if (cnt <= 0xffff)
break;
}
@@ -201,15 +204,16 @@ static int meson_pwm_calc(struct meson_pwm *meson,
if (duty == period) {
channel->pre_div = pre_div;
channel->hi = cnt;
channel->hi = cnt - 1;
channel->lo = 0;
} else if (duty == 0) {
channel->pre_div = pre_div;
channel->hi = 0;
channel->lo = cnt;
channel->lo = cnt - 1;
} else {
/* Then check is we can have the duty with the same pre_div */
duty_cnt = DIV_ROUND_CLOSEST(duty, fin_ns * (pre_div + 1));
duty_cnt = DIV_ROUND_CLOSEST_ULL((u64)duty * 1000,
fin_ps * (pre_div + 1));
if (duty_cnt > 0xffff) {
dev_err(meson->chip.dev, "unable to get duty cycle\n");
return -EINVAL;