linux-kernel - Re: [PATCH 1/3] iio: trigger: stm32-timer: preset shouldn't be buffered

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Date:   Sun, 24 Sep 2017 13:09:05 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Fabrice Gasnier <fabrice.gasnier@...com>
Cc:     <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <mcoquelin.stm32@...il.com>,
        <alexandre.torgue@...com>, <benjamin.gaignard@...com>,
        <benjamin.gaignard@...aro.org>, <linux-iio@...r.kernel.org>,
        <lars@...afoo.de>, <knaack.h@....de>, <pmeerw@...erw.net>
Subject: Re: [PATCH 1/3] iio: trigger: stm32-timer: preset shouldn't be
 buffered

On Mon, 18 Sep 2017 12:05:30 +0200
Fabrice Gasnier <fabrice.gasnier@...com> wrote:

> Currently, setting preset value (ARR) will update directly 'Auto reload
> value' only on 1st write access. But then, ARPE is set. This makes
> ARR a shadow register. Preset value should be updated upon each
> write request: ensure ARPE is 0. This fixes successive writes to
> preset attribute.
> 
> Fixes: 4adec7da0536 ("iio: stm32 trigger: Add quadrature encoder device")
> 
> Signed-off-by: Fabrice Gasnier <fabrice.gasnier@...com>

Applied to the fixes-togreg-post-rc1 branch of iio.git and marked
for stable.

Thanks,

Jonathan

> ---
>  drivers/iio/trigger/stm32-timer-trigger.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iio/trigger/stm32-timer-trigger.c b/drivers/iio/trigger/stm32-timer-trigger.c
> index 9b90534..34cc25b 100644
> --- a/drivers/iio/trigger/stm32-timer-trigger.c
> +++ b/drivers/iio/trigger/stm32-timer-trigger.c
> @@ -715,8 +715,9 @@ static ssize_t stm32_count_set_preset(struct iio_dev *indio_dev,
>  	if (ret)
>  		return ret;
>  
> +	/* TIMx_ARR register shouldn't be buffered (ARPE=0) */
> +	regmap_update_bits(priv->regmap, TIM_CR1, TIM_CR1_ARPE, 0);
>  	regmap_write(priv->regmap, TIM_ARR, preset);
> -	regmap_update_bits(priv->regmap, TIM_CR1, TIM_CR1_ARPE, TIM_CR1_ARPE);
>  
>  	return len;
>  }