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SubjectRe: [PATCH 07/12] i2c: qup: use the complete transfer length to choose DMA mode
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Tested on Centriq 2400

Reviewed-by: Austin Christ <austinwc@codeaurora.org>

On 2/3/2018 12:58 AM, Abhishek Sahu wrote:
> 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;
>

--
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