i2c: imx: separate atomic, dma and non-dma use case

JIRA: https://issues.redhat.com/browse/RHEL-116101

commit b460b15
Author: Stefan Eichenberger <stefan.eichenberger@toradex.com>
Date:   Mon Oct 14 15:15:13 2024 +0200

    i2c: imx: separate atomic, dma and non-dma use case

    Separate the atomic, dma and non-dma use case as a preparation step for
    moving the non-dma use case to the isr to avoid rescheduling while a
    transfer is in progress.

    Signed-off-by: Stefan Eichenberger <stefan.eichenberger@toradex.com>
    Reviewed-by: Frank Li <Frank.Li@nxp.com>
    Acked-by: Oleksij Rempel <o.rempel@pengutronix.de>
    Signed-off-by: Andi Shyti <andi.shyti@kernel.org>

Signed-off-by: Jared Kangas <jkangas@redhat.com>

Author: rh-jkangas

drivers/i2c/busses/i2c-imx.c

@@ -1011,6 +1011,43 @@ static int i2c_imx_dma_write(struct imx_i2c_struct *i2c_imx,
 	return i2c_imx_acked(i2c_imx);
 }
 
+static int i2c_imx_prepare_read(struct imx_i2c_struct *i2c_imx,
+				struct i2c_msg *msgs, bool atomic,
+				bool use_dma)
+{
+	int result;
+	unsigned int temp = 0;
+
+	/* write slave address */
+	imx_i2c_write_reg(i2c_8bit_addr_from_msg(msgs), i2c_imx, IMX_I2C_I2DR);
+	result = i2c_imx_trx_complete(i2c_imx, atomic);
+	if (result)
+		return result;
+	result = i2c_imx_acked(i2c_imx);
+	if (result)
+		return result;
+
+	dev_dbg(&i2c_imx->adapter.dev, "<%s> setup bus\n", __func__);
+
+	/* setup bus to read data */
+	temp = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2CR);
+	temp &= ~I2CR_MTX;
+
+	/*
+	 * Reset the I2CR_TXAK flag initially for SMBus block read since the
+	 * length is unknown
+	 */
+	if (msgs->len - 1)
+		temp &= ~I2CR_TXAK;
+	if (use_dma)
+		temp |= I2CR_DMAEN;
+
+	imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2CR);
+	imx_i2c_read_reg(i2c_imx, IMX_I2C_I2DR); /* dummy read */
+
+	return 0;
+}
+
 static int i2c_imx_dma_read(struct imx_i2c_struct *i2c_imx,
 			struct i2c_msg *msgs, bool is_lastmsg)
 {
@@ -1021,6 +1058,11 @@ static int i2c_imx_dma_read(struct imx_i2c_struct *i2c_imx,
 	struct imx_i2c_dma *dma = i2c_imx->dma;
 	struct device *dev = &i2c_imx->adapter.dev;
 
+	result = i2c_imx_prepare_read(i2c_imx, msgs, false, true);
+	if (result)
+		return result;
+
+	dev_dbg(&i2c_imx->adapter.dev, "<%s> read data\n", __func__);
 
 	dma->chan_using = dma->chan_rx;
 	dma->dma_transfer_dir = DMA_DEV_TO_MEM;
@@ -1131,50 +1173,24 @@ static int i2c_imx_write(struct imx_i2c_struct *i2c_imx, struct i2c_msg *msgs,
 	return 0;
 }
 
+static int i2c_imx_atomic_write(struct imx_i2c_struct *i2c_imx, struct i2c_msg *msgs)
+{
+	return i2c_imx_write(i2c_imx, msgs, true);
+}
+
 static int i2c_imx_read(struct imx_i2c_struct *i2c_imx, struct i2c_msg *msgs,
 			bool is_lastmsg, bool atomic)
 {
 	int i, result;
 	unsigned int temp;
 	int block_data = msgs->flags & I2C_M_RECV_LEN;
-	int use_dma = i2c_imx->dma && msgs->flags & I2C_M_DMA_SAFE &&
-		msgs->len >= DMA_THRESHOLD && !block_data;
 
-	dev_dbg(&i2c_imx->adapter.dev,
-		"<%s> write slave address: addr=0x%x\n",
-		__func__, i2c_8bit_addr_from_msg(msgs));
-
-	/* write slave address */
-	imx_i2c_write_reg(i2c_8bit_addr_from_msg(msgs), i2c_imx, IMX_I2C_I2DR);
-	result = i2c_imx_trx_complete(i2c_imx, atomic);
+	result = i2c_imx_prepare_read(i2c_imx, msgs, atomic, false);
 	if (result)
 		return result;
-	result = i2c_imx_acked(i2c_imx);
-	if (result)
-		return result;
-
-	dev_dbg(&i2c_imx->adapter.dev, "<%s> setup bus\n", __func__);
-
-	/* setup bus to read data */
-	temp = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2CR);
-	temp &= ~I2CR_MTX;
-
-	/*
-	 * Reset the I2CR_TXAK flag initially for SMBus block read since the
-	 * length is unknown
-	 */
-	if ((msgs->len - 1) || block_data)
-		temp &= ~I2CR_TXAK;
-	if (use_dma)
-		temp |= I2CR_DMAEN;
-	imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2CR);
-	imx_i2c_read_reg(i2c_imx, IMX_I2C_I2DR); /* dummy read */
 
 	dev_dbg(&i2c_imx->adapter.dev, "<%s> read data\n", __func__);
 
-	if (use_dma)
-		return i2c_imx_dma_read(i2c_imx, msgs, is_lastmsg);
-
 	/* read data */
 	for (i = 0; i < msgs->len; i++) {
 		u8 len = 0;
@@ -1241,13 +1257,20 @@ static int i2c_imx_read(struct imx_i2c_struct *i2c_imx, struct i2c_msg *msgs,
 	return 0;
 }
 
+static int i2c_imx_atomic_read(struct imx_i2c_struct *i2c_imx, struct i2c_msg *msgs,
+			       bool is_lastmsg)
+{
+	return i2c_imx_read(i2c_imx, msgs, is_lastmsg, true);
+}
+
 static int i2c_imx_xfer_common(struct i2c_adapter *adapter,
 			       struct i2c_msg *msgs, int num, bool atomic)
 {
 	unsigned int i, temp;
 	int result;
 	bool is_lastmsg = false;
 	struct imx_i2c_struct *i2c_imx = i2c_get_adapdata(adapter);
+	int use_dma = 0;
 
 	/* Start I2C transfer */
 	result = i2c_imx_start(i2c_imx, atomic);
@@ -1300,15 +1323,25 @@ static int i2c_imx_xfer_common(struct i2c_adapter *adapter,
 			(temp & I2SR_SRW ? 1 : 0), (temp & I2SR_IIF ? 1 : 0),
 			(temp & I2SR_RXAK ? 1 : 0));
 #endif
+
+		use_dma = i2c_imx->dma && msgs[i].len >= DMA_THRESHOLD &&
+			msgs[i].flags & I2C_M_DMA_SAFE;
 		if (msgs[i].flags & I2C_M_RD) {
-			result = i2c_imx_read(i2c_imx, &msgs[i], is_lastmsg, atomic);
+			int block_data = msgs->flags & I2C_M_RECV_LEN;
+
+			if (atomic)
+				result = i2c_imx_atomic_read(i2c_imx, &msgs[i], is_lastmsg);
+			else if (use_dma && !block_data)
+				result = i2c_imx_dma_read(i2c_imx, &msgs[i], is_lastmsg);
+			else
+				result = i2c_imx_read(i2c_imx, &msgs[i], is_lastmsg, false);
 		} else {
-			if (!atomic &&
-			    i2c_imx->dma && msgs[i].len >= DMA_THRESHOLD &&
-				msgs[i].flags & I2C_M_DMA_SAFE)
+			if (atomic)
+				result = i2c_imx_atomic_write(i2c_imx, &msgs[i]);
+			else if (use_dma)
 				result = i2c_imx_dma_write(i2c_imx, &msgs[i]);
 			else
-				result = i2c_imx_write(i2c_imx, &msgs[i], atomic);
+				result = i2c_imx_write(i2c_imx, &msgs[i], false);
 		}
 		if (result)
 			goto fail0;