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    Subject[PATCH 5/9] dmaengine: stm32-dma: Rework starting transfer management
    Date
    This patch reworks the way to manage transfer starting.
    Now, starting DMA is only allowed when the channel is not busy.
    Then, stm32_dma_start_transfer is declared as void.
    At least, after each transfer completion, we start the next transfer if a
    new descriptor as been queued in the issued list during an ongoing
    transfer.

    Signed-off-by: M'boumba Cedric Madianga <cedric.madianga@gmail.com>
    Reviewed-by: Ludovic BARRE <ludovic.barre@st.com>
    ---
    drivers/dma/stm32-dma.c | 20 +++++++++-----------
    1 file changed, 9 insertions(+), 11 deletions(-)

    diff --git a/drivers/dma/stm32-dma.c b/drivers/dma/stm32-dma.c
    index 3056ce7..adb846c 100644
    --- a/drivers/dma/stm32-dma.c
    +++ b/drivers/dma/stm32-dma.c
    @@ -421,7 +421,7 @@ static void stm32_dma_dump_reg(struct stm32_dma_chan *chan)
    dev_dbg(chan2dev(chan), "SFCR: 0x%08x\n", sfcr);
    }

    -static int stm32_dma_start_transfer(struct stm32_dma_chan *chan)
    +static void stm32_dma_start_transfer(struct stm32_dma_chan *chan)
    {
    struct stm32_dma_device *dmadev = stm32_dma_get_dev(chan);
    struct virt_dma_desc *vdesc;
    @@ -432,12 +432,12 @@ static int stm32_dma_start_transfer(struct stm32_dma_chan *chan)

    ret = stm32_dma_disable_chan(chan);
    if (ret < 0)
    - return ret;
    + return;

    if (!chan->desc) {
    vdesc = vchan_next_desc(&chan->vchan);
    if (!vdesc)
    - return -EPERM;
    + return;

    chan->desc = to_stm32_dma_desc(vdesc);
    chan->next_sg = 0;
    @@ -471,7 +471,7 @@ static int stm32_dma_start_transfer(struct stm32_dma_chan *chan)

    chan->busy = true;

    - return 0;
    + dev_dbg(chan2dev(chan), "vchan %p: started\n", &chan->vchan);
    }

    static void stm32_dma_configure_next_sg(struct stm32_dma_chan *chan)
    @@ -552,15 +552,13 @@ static void stm32_dma_issue_pending(struct dma_chan *c)
    {
    struct stm32_dma_chan *chan = to_stm32_dma_chan(c);
    unsigned long flags;
    - int ret;

    spin_lock_irqsave(&chan->vchan.lock, flags);
    - if (!chan->busy) {
    - if (vchan_issue_pending(&chan->vchan) && !chan->desc) {
    - ret = stm32_dma_start_transfer(chan);
    - if ((!ret) && (chan->desc->cyclic))
    - stm32_dma_configure_next_sg(chan);
    - }
    + if (vchan_issue_pending(&chan->vchan) && !chan->desc && !chan->busy) {
    + dev_dbg(chan2dev(chan), "vchan %p: issued\n", &chan->vchan);
    + stm32_dma_start_transfer(chan);
    + if (chan->desc->cyclic)
    + stm32_dma_configure_next_sg(chan);
    }
    spin_unlock_irqrestore(&chan->vchan.lock, flags);
    }
    --
    1.9.1
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