[PATCH v4 3/3] i2c: stm32f7: support i2c_*_dma_safe_msg_buf APIs

[Clément Le Goffic]

`i2c_*_dma_safe_msg_buf` APIs operate on a `struct i2c_msg`.
The get operation make sure the I2C buffer is DMA'able according to its
buffer length, or if the memory use is DMA coherent for example and
return a valid pointer for safe DMA access to be used.
The put operation release the pointer.
Prefer using generic API's than relying on private tests.

Acked-by: Alain Volmat <alain.vol...@foss.st.com>
Signed-off-by: Clément Le Goffic <clement.legof...@foss.st.com>
---
 drivers/i2c/busses/i2c-stm32f7.c | 32 +++++++++++++++++++++-----------
 1 file changed, 21 insertions(+), 11 deletions(-)

diff --git a/drivers/i2c/busses/i2c-stm32f7.c b/drivers/i2c/busses/i2c-stm32f7.c
index 73a7b8894c0d..994232646789 100644
--- a/drivers/i2c/busses/i2c-stm32f7.c
+++ b/drivers/i2c/busses/i2c-stm32f7.c
@@ -741,11 +741,14 @@ static void stm32f7_i2c_dma_callback(void *arg)
 {
        struct stm32f7_i2c_dev *i2c_dev = arg;
        struct stm32_i2c_dma *dma = i2c_dev->dma;
+       struct stm32f7_i2c_msg *f7_msg = &i2c_dev->f7_msg;
 
        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);
+       if (!f7_msg->smbus)
+               i2c_put_dma_safe_msg_buf(f7_msg->buf, i2c_dev->msg, true);
        complete(&dma->dma_complete);
 }
 
@@ -881,6 +884,7 @@ 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;
 
@@ -930,17 +934,23 @@ 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) {

-- 
2.43.0