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Subject[PATCH 07/12] i2c: qup: use the complete transfer length to choose DMA mode
Date
Currently each message length in complete transfer is being
checked for determining DMA mode and if any of the message length
is less than FIFO length then non DMA mode is being used which
will increase overhead. DMA can be used for any length and it
should be determined with complete transfer length. Now, this
patch introduces DMA threshold length and the transfer will be
done in DMA mode if the total length is greater than this
threshold length.

Signed-off-by: Abhishek Sahu <absahu@codeaurora.org>
---
drivers/i2c/busses/i2c-qup.c | 15 +++++++++------
1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/drivers/i2c/busses/i2c-qup.c b/drivers/i2c/busses/i2c-qup.c
index 6227a5c..a91fc70 100644
--- a/drivers/i2c/busses/i2c-qup.c
+++ b/drivers/i2c/busses/i2c-qup.c
@@ -192,6 +192,8 @@ struct qup_i2c_dev {
bool is_dma;
/* To check if the current transfer is using DMA */
bool use_dma;
+ /* The threshold length above which DMA will be used */
+ unsigned int dma_threshold;
struct dma_pool *dpool;
struct qup_i2c_tag start_tag;
struct qup_i2c_bam brx;
@@ -1294,7 +1296,8 @@ static int qup_i2c_xfer_v2(struct i2c_adapter *adap,
int num)
{
struct qup_i2c_dev *qup = i2c_get_adapdata(adap);
- int ret, len, idx = 0;
+ int ret, idx = 0;
+ unsigned int total_len = 0;

qup->bus_err = 0;
qup->qup_err = 0;
@@ -1320,14 +1323,13 @@ static int qup_i2c_xfer_v2(struct i2c_adapter *adap,
goto out;
}

- len = (msgs[idx].len > qup->out_fifo_sz) ||
- (msgs[idx].len > qup->in_fifo_sz);
-
- if (is_vmalloc_addr(msgs[idx].buf) || !len)
+ if (is_vmalloc_addr(msgs[idx].buf))
break;
+
+ total_len += msgs[idx].len;
}

- if (idx == num)
+ if (idx == num && total_len > qup->dma_threshold)
qup->use_dma = true;
}

@@ -1587,6 +1589,7 @@ static int qup_i2c_probe(struct platform_device *pdev)

size = QUP_INPUT_FIFO_SIZE(io_mode);
qup->in_fifo_sz = qup->in_blk_sz * (2 << size);
+ qup->dma_threshold = min(qup->out_fifo_sz, qup->in_fifo_sz);

fs_div = ((src_clk_freq / clk_freq) / 2) - 3;
hs_div = 3;
--
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation
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