Re: [PATCH 3/3] i2c: stm32f7: support i2c_*_dma_safe_msg_buf APIs

[Alain Volmat <alain.volmat@foss.st.com>]

Hi Clément,

thanks for the patch.

On Mon, Jun 16, 2025 at 10:53:56AM +0200, Clément Le Goffic wrote:
> Use the i2c-core-base APIs to allocate a DMA safe buffer when needed.
> 
> Signed-off-by: Clément Le Goffic <clement.legoffic@foss.st.com>
> ---
>  drivers/i2c/busses/i2c-stm32f7.c | 36 +++++++++++++++++++++++++-----------
>  1 file changed, 25 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-stm32f7.c b/drivers/i2c/busses/i2c-stm32f7.c
> index a05cac5ee9db..5be14c8a2af4 100644
> --- a/drivers/i2c/busses/i2c-stm32f7.c
> +++ b/drivers/i2c/busses/i2c-stm32f7.c
> @@ -742,9 +742,12 @@ static void stm32f7_i2c_dma_callback(void *arg)
>  	struct stm32f7_i2c_dev *i2c_dev = (struct stm32f7_i2c_dev *)arg;
>  	struct stm32_i2c_dma *dma = i2c_dev->dma;
>  	struct device *dev = dma->chan_using->device->dev;
> +	struct stm32f7_i2c_msg *f7_msg = &i2c_dev->f7_msg;
>  
>  	stm32f7_i2c_disable_dma_req(i2c_dev);
>  	dma_unmap_single(dev, dma->dma_buf, dma->dma_len, dma->dma_data_dir);
> +	if (!f7_msg->smbus)
> +		i2c_put_dma_safe_msg_buf(f7_msg->buf, i2c_dev->msg, true);
>  	complete(&dma->dma_complete);
>  }
>  
> @@ -880,6 +883,7 @@ static void stm32f7_i2c_xfer_msg(struct stm32f7_i2c_dev *i2c_dev,
>  {
>  	struct stm32f7_i2c_msg *f7_msg = &i2c_dev->f7_msg;
>  	void __iomem *base = i2c_dev->base;
> +	u8 *dma_buf;
>  	u32 cr1, cr2;
>  	int ret;
>  
> @@ -929,17 +933,23 @@ static void stm32f7_i2c_xfer_msg(struct stm32f7_i2c_dev *i2c_dev,
>  
>  	/* Configure DMA or enable RX/TX interrupt */
>  	i2c_dev->use_dma = false;
> -	if (i2c_dev->dma && f7_msg->count >= STM32F7_I2C_DMA_LEN_MIN
> -	    && !i2c_dev->atomic) {
> -		ret = stm32_i2c_prep_dma_xfer(i2c_dev->dev, i2c_dev->dma,
> -					      msg->flags & I2C_M_RD,
> -					      f7_msg->count, f7_msg->buf,
> -					      stm32f7_i2c_dma_callback,
> -					      i2c_dev);
> -		if (!ret)
> -			i2c_dev->use_dma = true;
> -		else
> -			dev_warn(i2c_dev->dev, "can't use DMA\n");
> +	if (i2c_dev->dma && !i2c_dev->atomic) {
> +		dma_buf = i2c_get_dma_safe_msg_buf(msg, STM32F7_I2C_DMA_LEN_MIN);
> +		if (dma_buf) {
> +			f7_msg->buf = dma_buf;
> +			ret = stm32_i2c_prep_dma_xfer(i2c_dev->dev, i2c_dev->dma,
> +						      msg->flags & I2C_M_RD,
> +						      f7_msg->count, f7_msg->buf,
> +						      stm32f7_i2c_dma_callback,
> +						      i2c_dev);
> +			if (ret) {
> +				dev_warn(i2c_dev->dev, "can't use DMA\n");
> +				i2c_put_dma_safe_msg_buf(f7_msg->buf, msg, false);
> +				f7_msg->buf = msg->buf;
> +			} else {
> +				i2c_dev->use_dma = true;
> +			}
> +		}
>  	}
>  
>  	if (!i2c_dev->use_dma) {
> @@ -1624,6 +1634,8 @@ static irqreturn_t stm32f7_i2c_isr_event_thread(int irq, void *data)
>  			dmaengine_terminate_async(dma->chan_using);
>  			dma_unmap_single(i2c_dev->dev, dma->dma_buf, dma->dma_len,
>  					 dma->dma_data_dir);
> +			if (!f7_msg->smbus)
> +				i2c_put_dma_safe_msg_buf(f7_msg->buf, i2c_dev->msg, false);
>  		}
>  		f7_msg->result = -ENXIO;
>  	}
> @@ -1646,6 +1658,8 @@ static irqreturn_t stm32f7_i2c_isr_event_thread(int irq, void *data)
>  				dmaengine_terminate_async(dma->chan_using);
>  				dma_unmap_single(i2c_dev->dev, dma->dma_buf, dma->dma_len,
>  						 dma->dma_data_dir);
> +				if (!f7_msg->smbus)
> +					i2c_put_dma_safe_msg_buf(f7_msg->buf, i2c_dev->msg, false);
>  				f7_msg->result = -ETIMEDOUT;
>  			}
>  		}
> 

Looks good to me.

Acked-by: Alain Volmat <alain.volmat@foss.st.com>

Regards,
Alain

> -- 
> 2.43.0
>