Subject: Re: [PATCH] i2c: stm32f7: fix timing computation ignoring i2c-analog-filter

From: Alain Volmat <[email-masked]>
Date: Wed, 3 Jun 2026 10:59:14 +0200

Hi,

thank you for you patch.

On Tue, May 26, 2026 at 11:12:09AM +0200, Guillermo Rodríguez wrote:
> stm32f7_i2c_compute_timing() uses i2c_dev->analog_filter to pick
> the analog filter delay, but i2c_dev->analog_filter is parsed from
> the "i2c-analog-filter" DT property only after the compute_timing
> loop in stm32f7_i2c_setup_timing(), so in practice the timing
> calculations always ignore the analog filter. On an STM32MP1 board
> with clock-frequency = <400000> and i2c-analog-filter set, measured
> SCL frequency was ~382 kHz.
> 
> This also affects (widens) the computed SDADEL range. At high bus
> clock speeds, this can select an SDADEL value that violates tVD;DAT
> (data valid time).
> 
> Fix by parsing "i2c-analog-filter" before the compute_timing loop.
> 
> Fixes: 83c3408f7b9c ("i2c: stm32f7: support DT binding i2c-analog-filter")
> Cc: [email-masked]
> Signed-off-by: Guillermo Rodríguez <[email-masked]>
> ---
>  drivers/i2c/busses/i2c-stm32f7.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-stm32f7.c b/drivers/i2c/busses/i2c-stm32f7.c
> index 53d9df70ebe4..067af255bd22 100644
> --- a/drivers/i2c/busses/i2c-stm32f7.c
> +++ b/drivers/i2c/busses/i2c-stm32f7.c
> @@ -694,6 +694,9 @@ static int stm32f7_i2c_setup_timing(struct stm32f7_i2c_dev *i2c_dev,
>  	if (!of_property_read_bool(i2c_dev->dev->of_node, "i2c-digital-filter"))
>  		i2c_dev->dnf_dt = STM32F7_I2C_DNF_DEFAULT;
>  
> +	i2c_dev->analog_filter = of_property_read_bool(i2c_dev->dev->of_node,
> +						       "i2c-analog-filter");
> +
>  	do {
>  		ret = stm32f7_i2c_compute_timing(i2c_dev, setup,
>  						 &i2c_dev->timing);
> @@ -715,9 +718,6 @@ static int stm32f7_i2c_setup_timing(struct stm32f7_i2c_dev *i2c_dev,
>  		return ret;
>  	}
>  
> -	i2c_dev->analog_filter = of_property_read_bool(i2c_dev->dev->of_node,
> -						       "i2c-analog-filter");
> -
>  	dev_dbg(i2c_dev->dev, "I2C Speed(%i), Clk Source(%i)\n",
>  		setup->speed_freq, setup->clock_src);
>  	dev_dbg(i2c_dev->dev, "I2C Rise(%i) and Fall(%i) Time\n",
> -- 
> 2.25.1
> 

Acked-by: Alain Volmat <[email-masked]>

Regards,
Alain