i2c: stm32f7: unmap DMA mapped buffer

Before each I2C transfer using DMA, the I2C buffer is DMA'pped to make
sure the memory buffer is DMA'able. This is handle in the function
`stm32_i2c_prep_dma_xfer()`.
If the transfer fails for any reason the I2C buffer must be unmap.
Use the dma_callback to factorize the code and fix this issue.

Note that the `stm32f7_i2c_dma_callback()` is now called in case of DMA
transfer success and error and that the `complete()` on the dma_complete
completion structure is done inconditionnally in case of transfer
success or error as well as the `dmaengine_terminate_async()`.
This is allowed as a `complete()` in case transfer error has no effect
as well as a `dmaengine_terminate_async()` on a transfer success.

Also fix the unneeded cast and remove not more needed variables.

Fixes: 7ecc8cfde553 ("i2c: i2c-stm32f7: Add DMA support")
Signed-off-by: Clément Le Goffic <[e-mail]>
Cc: <[e-mail]> # v4.18+
Acked-by: Alain Volmat <[e-mail]>
Signed-off-by: Andi Shyti <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

drivers/i2c/busses/i2c-stm32f7.c

···
 
 static void stm32f7_i2c_dma_callback(void *arg)
 {
-	struct stm32f7_i2c_dev *i2c_dev = (struct stm32f7_i2c_dev *)arg;
+	struct stm32f7_i2c_dev *i2c_dev = arg;
 	struct stm32_i2c_dma *dma = i2c_dev->dma;
 
 	stm32f7_i2c_disable_dma_req(i2c_dev);
+	dmaengine_terminate_async(dma->chan_using);
 	dma_unmap_single(i2c_dev->dev, dma->dma_buf, dma->dma_len,
 			 dma->dma_data_dir);
 	complete(&dma->dma_complete);
···
 	u16 addr = f7_msg->addr;
 	void __iomem *base = i2c_dev->base;
 	struct device *dev = i2c_dev->dev;
-	struct stm32_i2c_dma *dma = i2c_dev->dma;
 
 	/* Bus error */
 	if (status & STM32F7_I2C_ISR_BERR) {
···
 	}
 
 	/* Disable dma */
-	if (i2c_dev->use_dma) {
-		stm32f7_i2c_disable_dma_req(i2c_dev);
-		dmaengine_terminate_async(dma->chan_using);
-	}
+	if (i2c_dev->use_dma)
+		stm32f7_i2c_dma_callback(i2c_dev);
 
 	i2c_dev->master_mode = false;
 	complete(&i2c_dev->complete);
···
 {
 	struct stm32f7_i2c_dev *i2c_dev = data;
 	struct stm32f7_i2c_msg *f7_msg = &i2c_dev->f7_msg;
-	struct stm32_i2c_dma *dma = i2c_dev->dma;
 	void __iomem *base = i2c_dev->base;
 	u32 status, mask;
 	int ret;
···
 		dev_dbg(i2c_dev->dev, "<%s>: Receive NACK (addr %x)\n",
 			__func__, f7_msg->addr);
 		writel_relaxed(STM32F7_I2C_ICR_NACKCF, base + STM32F7_I2C_ICR);
-		if (i2c_dev->use_dma) {
-			stm32f7_i2c_disable_dma_req(i2c_dev);
-			dmaengine_terminate_async(dma->chan_using);
-		}
+		if (i2c_dev->use_dma)
+			stm32f7_i2c_dma_callback(i2c_dev);
 		f7_msg->result = -ENXIO;
 	}
 
···
 			ret = wait_for_completion_timeout(&i2c_dev->dma->dma_complete, HZ);
 			if (!ret) {
 				dev_dbg(i2c_dev->dev, "<%s>: Timed out\n", __func__);
-				stm32f7_i2c_disable_dma_req(i2c_dev);
-				dmaengine_terminate_async(dma->chan_using);
+				stm32f7_i2c_dma_callback(i2c_dev);
 				f7_msg->result = -ETIMEDOUT;
 			}
 		}