i2c: mediatek: modify threshold passed to i2c_get_dma_safe_msg_buf()

DMA with zero-length transfers doesn't make sense and this HW doesn't
support them at all, so increase the threshold.

Fixes: fc66b39f ("i2c: mediatek: Use DMA safe buffers for i2c transactions")
Signed-off-by: Hsin-Yi Wang <hsinyi@chromium.org>
[wsa: reworded commit message]
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

drivers/i2c/busses/i2c-mt65xx.c

@@ -503,7 +503,7 @@ static int mtk_i2c_do_transfer(struct mtk_i2c *i2c, struct i2c_msg *msgs,
 		writel(I2C_DMA_INT_FLAG_NONE, i2c->pdmabase + OFFSET_INT_FLAG);
 		writel(I2C_DMA_CON_RX, i2c->pdmabase + OFFSET_CON);
 
-		dma_rd_buf = i2c_get_dma_safe_msg_buf(msgs, 0);
+		dma_rd_buf = i2c_get_dma_safe_msg_buf(msgs, 1);
 		if (!dma_rd_buf)
 			return -ENOMEM;
 
@@ -526,7 +526,7 @@ static int mtk_i2c_do_transfer(struct mtk_i2c *i2c, struct i2c_msg *msgs,
 		writel(I2C_DMA_INT_FLAG_NONE, i2c->pdmabase + OFFSET_INT_FLAG);
 		writel(I2C_DMA_CON_TX, i2c->pdmabase + OFFSET_CON);
 
-		dma_wr_buf = i2c_get_dma_safe_msg_buf(msgs, 0);
+		dma_wr_buf = i2c_get_dma_safe_msg_buf(msgs, 1);
 		if (!dma_wr_buf)
 			return -ENOMEM;
 
@@ -549,7 +549,7 @@ static int mtk_i2c_do_transfer(struct mtk_i2c *i2c, struct i2c_msg *msgs,
 		writel(I2C_DMA_CLR_FLAG, i2c->pdmabase + OFFSET_INT_FLAG);
 		writel(I2C_DMA_CLR_FLAG, i2c->pdmabase + OFFSET_CON);
 
-		dma_wr_buf = i2c_get_dma_safe_msg_buf(msgs, 0);
+		dma_wr_buf = i2c_get_dma_safe_msg_buf(msgs, 1);
 		if (!dma_wr_buf)
 			return -ENOMEM;
 
@@ -561,7 +561,7 @@ static int mtk_i2c_do_transfer(struct mtk_i2c *i2c, struct i2c_msg *msgs,
 			return -ENOMEM;
 		}
 
-		dma_rd_buf = i2c_get_dma_safe_msg_buf((msgs + 1), 0);
+		dma_rd_buf = i2c_get_dma_safe_msg_buf((msgs + 1), 1);
 		if (!dma_rd_buf) {
 			dma_unmap_single(i2c->dev, wpaddr,
 					 msgs->len, DMA_TO_DEVICE);