From: Sean Wang <[email protected]>
Add a way that turning resolution from in nanosecond into in picosecond
to improve noticeably almost 4.5% precision.
It's necessary to hold the new resolution with type u64 and thus related
operations on u64 are applied instead in those rate calculations.
And the patch has a dependency on [1].
[1] http://lists.infradead.org/pipermail/linux-mediatek/2018-March/012225.html
Cc: [email protected]
Fixes: caf065f8fd58 ("pwm: Add MediaTek PWM support")
Signed-off-by: Sean Wang <[email protected]>
---
drivers/pwm/pwm-mediatek.c | 17 ++++++++++++-----
1 file changed, 12 insertions(+), 5 deletions(-)
diff --git a/drivers/pwm/pwm-mediatek.c b/drivers/pwm/pwm-mediatek.c
index 796baea..98b0a93 100644
--- a/drivers/pwm/pwm-mediatek.c
+++ b/drivers/pwm/pwm-mediatek.c
@@ -135,19 +135,25 @@ static int mtk_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
{
struct mtk_pwm_chip *pc = to_mtk_pwm_chip(chip);
struct clk *clk = pc->clks[MTK_CLK_PWM1 + pwm->hwpwm];
- u32 resolution, clkdiv = 0, reg_width = PWMDWIDTH,
+ u32 clkdiv = 0, cnt_period, cnt_duty, reg_width = PWMDWIDTH,
reg_thres = PWMTHRES;
+ u64 resolution;
int ret;
ret = mtk_pwm_clk_enable(chip, pwm);
if (ret < 0)
return ret;
- resolution = NSEC_PER_SEC / clk_get_rate(clk);
+ /* Using resolution in picosecond gets accuracy higher */
+ resolution = (u64)NSEC_PER_SEC * 1000;
+ do_div(resolution, clk_get_rate(clk));
- while (period_ns / resolution > 8191) {
+ cnt_period = DIV_ROUND_CLOSEST_ULL((u64)period_ns * 1000, resolution);
+ while (cnt_period > 8191) {
resolution *= 2;
clkdiv++;
+ cnt_period = DIV_ROUND_CLOSEST_ULL((u64)period_ns * 1000,
+ resolution);
}
if (clkdiv > PWM_CLK_DIV_MAX) {
@@ -165,9 +171,10 @@ static int mtk_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
reg_thres = PWM45THRES_FIXUP;
}
+ cnt_duty = DIV_ROUND_CLOSEST_ULL((u64)duty_ns * 1000, resolution);
mtk_pwm_writel(pc, pwm->hwpwm, PWMCON, BIT(15) | clkdiv);
- mtk_pwm_writel(pc, pwm->hwpwm, reg_width, period_ns / resolution);
- mtk_pwm_writel(pc, pwm->hwpwm, reg_thres, duty_ns / resolution);
+ mtk_pwm_writel(pc, pwm->hwpwm, reg_width, cnt_period);
+ mtk_pwm_writel(pc, pwm->hwpwm, reg_thres, cnt_duty);
mtk_pwm_clk_disable(chip, pwm);
--
2.7.4
On Fri, Mar 02, 2018 at 04:49:14PM +0800, [email protected] wrote:
> From: Sean Wang <[email protected]>
>
> Add a way that turning resolution from in nanosecond into in picosecond
> to improve noticeably almost 4.5% precision.
>
> It's necessary to hold the new resolution with type u64 and thus related
> operations on u64 are applied instead in those rate calculations.
>
> And the patch has a dependency on [1].
>
> [1] http://lists.infradead.org/pipermail/linux-mediatek/2018-March/012225.html
>
> Cc: [email protected]
> Fixes: caf065f8fd58 ("pwm: Add MediaTek PWM support")
> Signed-off-by: Sean Wang <[email protected]>
> ---
> drivers/pwm/pwm-mediatek.c | 17 ++++++++++++-----
> 1 file changed, 12 insertions(+), 5 deletions(-)
Applied, thanks.
Thierry