On Thu, 2017-07-06 at 14:16 +0800, Zhi Mao wrote: > On Wed, 2017-07-05 at 13:09 +0200, Matthias Brugger wrote: > > > > On 06/30/2017 08:05 AM, Zhi Mao wrote: > > > In original code, the pwm output frequency is not correct > > > when set bit<3>=1 to PWMCON register. > > > > > > Signed-off-by: Zhi Mao <zhi.mao@xxxxxxxxxxxx> > > > --- > > > drivers/pwm/pwm-mediatek.c | 2 +- > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > diff --git a/drivers/pwm/pwm-mediatek.c b/drivers/pwm/pwm-mediatek.c > > > index 5c11bc7..d08b5b3 100644 > > > --- a/drivers/pwm/pwm-mediatek.c > > > +++ b/drivers/pwm/pwm-mediatek.c > > > @@ -91,7 +91,7 @@ static int mtk_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm, > > > if (clkdiv > 7) > > > return -EINVAL; > > > > > > - mtk_pwm_writel(pc, pwm->hwpwm, PWMCON, BIT(15) | BIT(3) | clkdiv); > > > + mtk_pwm_writel(pc, pwm->hwpwm, PWMCON, BIT(15) | clkdiv); > > > > Just for clarification, BIT(15) enables old PWM mode, which ignores > > CLKSEL (BIT(3)). Therefore setting BIT(3) does not have any effect and > > can be discarded. > > > > Am I correct? I took mt7623n datasheet for reference. > > > > Regards, > > Matthias > > > Yes, remove setting bit<3> will not take any effect. > PWMCON bit<3> is pwm source clock selecting register. > You can check the datasheet of MT7623 for details. > > Regards > Zhi > Hi Mattias, Ignore the above reply, I explain this bit<3> issue for you. In the data sheet of MT7623: PWMCON bit<3> is PWM source clock selecting register 0: CLK=CLKSRC 1: CLK=CLKSRC/1625 for example, bit<3>=0, PWM clk source is 26M bit<3>=1, PWM clk source is 16K The frequency of PWM output will based on this clock source if set bit<3>=1, it will cause the frequency of PWM output is not correct. I also use the oscilloscope device to measure the output, set bit<3>=0, the output meet expectation. Regards Zhi > > > mtk_pwm_writel(pc, pwm->hwpwm, PWMDWIDTH, period_ns / resolution); > > > mtk_pwm_writel(pc, pwm->hwpwm, PWMTHRES, duty_ns / resolution); > > > > > > > -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
