Re: [PATCH] pwm: stm32: enforce settings for pwm capture

[Lee Jones <lee@kernel.org>]

On Tue, 13 Dec 2022, Olivier Moysan wrote:

> The PWM capture assumes that the input selector is set to default
> input and that the slave mode is disabled. Force reset state for
> TISEL and SMCR registers to match this requirement.
> 
> Note that slave mode disabling is not a pre-requisite by itself
> for capture mode, as hardware supports it for PWM capture.
> However, the current implementation of the driver does not
> allow slave mode for PWM capture. Setting slave mode for PWM
> capture results in wrong capture values.
> 
> Fixes: 53e38fe73f94 ("pwm: stm32: Add capture support")
> Signed-off-by: Olivier Moysan <olivier.moysan@foss.st.com>
> ---
>  drivers/pwm/pwm-stm32.c          | 4 ++++
>  include/linux/mfd/stm32-timers.h | 1 +

Acked-by: Lee Jones <lee@kernel.org>

>  2 files changed, 5 insertions(+)
> 
> diff --git a/drivers/pwm/pwm-stm32.c b/drivers/pwm/pwm-stm32.c
> index 794ca5b02968..24aab0450c78 100644
> --- a/drivers/pwm/pwm-stm32.c
> +++ b/drivers/pwm/pwm-stm32.c
> @@ -207,6 +207,10 @@ static int stm32_pwm_capture(struct pwm_chip *chip, struct pwm_device *pwm,
>  	regmap_write(priv->regmap, TIM_ARR, priv->max_arr);
>  	regmap_write(priv->regmap, TIM_PSC, psc);
>  
> +	/* Reset input selector to its default input and disable slave mode */
> +	regmap_write(priv->regmap, TIM_TISEL, 0x0);
> +	regmap_write(priv->regmap, TIM_SMCR, 0x0);
> +
>  	/* Map TI1 or TI2 PWM input to IC1 & IC2 (or TI3/4 to IC3 & IC4) */
>  	regmap_update_bits(priv->regmap,
>  			   pwm->hwpwm < 2 ? TIM_CCMR1 : TIM_CCMR2,
> diff --git a/include/linux/mfd/stm32-timers.h b/include/linux/mfd/stm32-timers.h
> index 5f5c43fd69dd..1b94325febb3 100644
> --- a/include/linux/mfd/stm32-timers.h
> +++ b/include/linux/mfd/stm32-timers.h
> @@ -31,6 +31,7 @@
>  #define TIM_BDTR	0x44	/* Break and Dead-Time Reg */
>  #define TIM_DCR		0x48	/* DMA control register    */
>  #define TIM_DMAR	0x4C	/* DMA register for transfer */
> +#define TIM_TISEL	0x68	/* Input Selection         */
>  
>  #define TIM_CR1_CEN	BIT(0)	/* Counter Enable	   */
>  #define TIM_CR1_DIR	BIT(4)  /* Counter Direction	   */
> -- 
> 2.25.1
> 

-- 
Lee Jones [李琼斯]