linux-kernel - [PATCH 3/3] i2c: stm32f7: support i2c_*_dma_safe_msg

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Message-ID: <20250616-i2c-upstream-v1-3-42d3d5374e65@foss.st.com>
Date: Mon, 16 Jun 2025 10:53:56 +0200
From: Clément Le Goffic <clement.legoffic@...s.st.com>
To: Pierre-Yves MORDRET <pierre-yves.mordret@...s.st.com>,
        Alain Volmat
	<alain.volmat@...s.st.com>,
        Andi Shyti <andi.shyti@...nel.org>,
        "Maxime
 Coquelin" <mcoquelin.stm32@...il.com>,
        Alexandre Torgue
	<alexandre.torgue@...s.st.com>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Christian König <christian.koenig@....com>,
        "M'boumba Cedric
 Madianga" <cedric.madianga@...il.com>,
        Wolfram Sang <wsa@...nel.org>
CC: Pierre-Yves MORDRET <pierre-yves.mordret@...com>,
        <linux-i2c@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <linux-arm-kernel@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
        <linux-media@...r.kernel.org>, <dri-devel@...ts.freedesktop.org>,
        <linaro-mm-sig@...ts.linaro.org>,
        Clément Le Goffic
	<clement.legoffic@...s.st.com>
Subject: [PATCH 3/3] i2c: stm32f7: support i2c_*_dma_safe_msg_buf APIs

Use the i2c-core-base APIs to allocate a DMA safe buffer when needed.

Signed-off-by: Clément Le Goffic <clement.legoffic@...s.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;
 			}
 		}

-- 
2.43.0