The modulo register defines the period of the edge-aligned PWM mode
(which is the only mode implemented). The reference manual states:
"The EPWM period is determined by (MOD + 0001h) ..." So the value that
is written to the MOD register must therefore be one less than the
calculated period length.
A correct MODULO value is particularly relevant if the PWM has to output
a high frequency due to a low period value.

Signed-off-by: Erik Schumacher <erik.schumacher@iris-sensing.com>
---
 drivers/pwm/pwm-imx-tpm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/pwm/pwm-imx-tpm.c b/drivers/pwm/pwm-imx-tpm.c
index 96ea343856f0..a05b66ffe208 100644
--- a/drivers/pwm/pwm-imx-tpm.c
+++ b/drivers/pwm/pwm-imx-tpm.c
@@ -106,7 +106,7 @@ static int pwm_imx_tpm_round_state(struct pwm_chip *chip,
 	p->prescale = prescale;
 
 	period_count = (clock_unit + ((1 << prescale) >> 1)) >> prescale;
-	p->mod = period_count;
+	p->mod = period_count - 1;
 
 	/* calculate real period HW can support */
 	tmp = (u64)period_count << prescale;
-- 
2.47.0

On Wed, Oct 23, 2024 at 12:33:53PM +0000, Erik Schumacher wrote:
> The modulo register defines the period of the edge-aligned PWM mode
> (which is the only mode implemented). The reference manual states:
> "The EPWM period is determined by (MOD + 0001h) ..." So the value that
> is written to the MOD register must therefore be one less than the
> calculated period length.
> A correct MODULO value is particularly relevant if the PWM has to output
> a high frequency due to a low period value.
>
This is bug fix,  add fix tag and cc stable

Frank

> Signed-off-by: Erik Schumacher <erik.schumacher@iris-sensing.com>
> ---
>  drivers/pwm/pwm-imx-tpm.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/pwm/pwm-imx-tpm.c b/drivers/pwm/pwm-imx-tpm.c
> index 96ea343856f0..a05b66ffe208 100644
> --- a/drivers/pwm/pwm-imx-tpm.c
> +++ b/drivers/pwm/pwm-imx-tpm.c
> @@ -106,7 +106,7 @@ static int pwm_imx_tpm_round_state(struct pwm_chip *chip,
>  	p->prescale = prescale;
>
>  	period_count = (clock_unit + ((1 << prescale) >> 1)) >> prescale;
> -	p->mod = period_count;
> +	p->mod = period_count - 1;
>
>  	/* calculate real period HW can support */
>  	tmp = (u64)period_count << prescale;
> --
> 2.47.0
>

Am Mittwoch, dem 23.10.2024 um 11:35 -0400 schrieb Frank Li:
> On Wed, Oct 23, 2024 at 12:33:53PM +0000, Erik Schumacher wrote:
> > The modulo register defines the period of the edge-aligned PWM mode
> > (which is the only mode implemented). The reference manual states:
> > "The EPWM period is determined by (MOD + 0001h) ..." So the value that
> > is written to the MOD register must therefore be one less than the
> > calculated period length.
> > A correct MODULO value is particularly relevant if the PWM has to output
> > a high frequency due to a low period value.
> > 
> This is bug fix,  add fix tag and cc stable
> 
> Frank

That's true. I will do a v2 with these tags.
Thank you!

Erik
>