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Subject[PATCH 3/4] i2c: sh_mobile: use helper to decide if DMA is useful
Date
This ensures that we fall back to PIO if the buffer is too small for DMA
being useful. Otherwise, we use DMA. A bounce buffer might be applied if
the original message buffer is not DMA safe

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
---
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 2e097d97d258bc..4b874e508111e7 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 *bounce_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_bounce_buf(pd->msg, pd->bounce_buf);
+
iic_set_clr(pd, ICIC, 0, ICIC_TDMAE | ICIC_RDMAE);
}

@@ -595,6 +598,7 @@ static void sh_mobile_i2c_xfer_dma(struct sh_mobile_i2c_data *pd)
struct dma_async_tx_descriptor *txdesc;
dma_addr_t dma_addr;
dma_cookie_t cookie;
+ u8 *dma_buf = pd->bounce_buf ?: pd->msg->buf;

if (PTR_ERR(chan) == -EPROBE_DEFER) {
if (read)
@@ -608,7 +612,7 @@ 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, 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 +669,7 @@ 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)
+ if (i2c_check_msg_for_dma(pd->msg, 8, &pd->bounce_buf) == 0)
sh_mobile_i2c_xfer_dma(pd);

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