[PATCH v6 8/9] i2c: sh_mobile: use core helper to decide when to use DMA

Wolfram Sang
2017-11-04T20:20:08Z

This ensures that we fall back to PIO if the message length is too small
for DMA being useful. Otherwise, we use DMA. A bounce buffer might be
applied by the helper if the original message buffer is not DMA safe.

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
---
drivers/i2c/busses/i2c-sh_mobile.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/i2c/busses/i2c-sh_mobile.c b/drivers/i2c/busses/i2c-sh_mobile.c
index c03acdf7139726..fbadb861672b84 100644
--- a/drivers/i2c/busses/i2c-sh_mobile.c
+++ b/drivers/i2c/busses/i2c-sh_mobile.c
@@ -145,6 +145,7 @@ struct sh_mobile_i2c_data {
struct dma_chan *dma_rx;
struct scatterlist sg;
enum dma_data_direction dma_direction;
+ u8 *dma_buf;
};

struct sh_mobile_dt_config {
@@ -548,6 +549,8 @@ static void sh_mobile_i2c_dma_callback(void *data)
pd->pos = pd->msg->len;
pd->stop_after_dma = true;

+ i2c_release_dma_safe_msg_buf(pd->msg, pd->dma_buf);
+
iic_set_clr(pd, ICIC, 0, ICIC_TDMAE | ICIC_RDMAE);
}

@@ -608,7 +611,7 @@ static void sh_mobile_i2c_xfer_dma(struct sh_mobile_i2c_data *pd)
if (IS_ERR(chan))
return;

- dma_addr = dma_map_single(chan->device->dev, pd->msg->buf, pd->msg->len, dir);
+ dma_addr = dma_map_single(chan->device->dev, pd->dma_buf, pd->msg->len, dir);
if (dma_mapping_error(chan->device->dev, dma_addr)) {
dev_dbg(pd->dev, "dma map failed, using PIO\n");
return;
@@ -665,7 +668,8 @@ static int start_ch(struct sh_mobile_i2c_data *pd, struct i2c_msg *usr_msg,
pd->pos = -1;
pd->sr = 0;

- if (pd->msg->len > 8)
+ pd->dma_buf = i2c_get_dma_safe_msg_buf(pd->msg, 8);
+ if (pd->dma_buf)
sh_mobile_i2c_xfer_dma(pd);

/* Enable all interrupts to begin with */
--
2.11.0