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    Subject[PATCH V2 7/7] dmaengine/dw_dmac: implement pause and resume in dwc_control
    Date
    From: Linus Walleij <linus.walleij@linaro.org>

    Some peripherals like amba-pl011 needs pause to be implemented in DMA controller
    drivers. This also returns correct status from dwc_tx_status() in case chan is
    paused.

    Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
    Signed-off-by: Viresh Kumar <viresh.kumar@st.com>
    ---
    drivers/dma/dw_dmac.c | 25 +++++++++++++++++++++++--
    drivers/dma/dw_dmac_regs.h | 1 +
    2 files changed, 24 insertions(+), 2 deletions(-)

    diff --git a/drivers/dma/dw_dmac.c b/drivers/dma/dw_dmac.c
    index c30f0ba..48d2d7e 100644
    --- a/drivers/dma/dw_dmac.c
    +++ b/drivers/dma/dw_dmac.c
    @@ -832,8 +832,7 @@ static int dwc_control(struct dma_chan *chan, enum dma_ctrl_cmd cmd,
    struct dw_desc *desc, *_desc;
    LIST_HEAD(list);

    - /* Only supports DMA_TERMINATE_ALL */
    - if (cmd != DMA_TERMINATE_ALL)
    + if (cmd != DMA_TERMINATE_ALL && cmd != DMA_PAUSE && cmd != DMA_RESUME)
    return -ENXIO;

    /*
    @@ -844,11 +843,30 @@ static int dwc_control(struct dma_chan *chan, enum dma_ctrl_cmd cmd,
    */
    spin_lock_irqsave(&dwc->lock, dwc->lflags);

    + if (cmd == DMA_RESUME) {
    + if (dwc->paused) {
    + channel_set_bit(dw, CH_EN, dwc->mask);
    + while (!(dma_readl(dw, CH_EN) & dwc->mask))
    + cpu_relax();
    + }
    + spin_unlock_irqrestore(&dwc->lock, dwc->lflags);
    + return 0;
    + }
    +
    channel_clear_bit(dw, CH_EN, dwc->mask);

    while (dma_readl(dw, CH_EN) & dwc->mask)
    cpu_relax();

    + if (cmd == DMA_PAUSE) {
    + dwc->paused = true;
    + spin_unlock_irqrestore(&dwc->lock, dwc->lflags);
    + return 0;
    + }
    +
    + /* Terminating a paused transfer */
    + dwc->paused = false;
    +
    /* active_list entries will end up before queued entries */
    list_splice_init(&dwc->queue, &list);
    list_splice_init(&dwc->active_list, &list);
    @@ -893,6 +911,9 @@ dwc_tx_status(struct dma_chan *chan,
    else
    dma_set_tx_state(txstate, last_complete, last_used, 0);

    + if (dwc->paused)
    + return DMA_PAUSED;
    +
    return ret;
    }

    diff --git a/drivers/dma/dw_dmac_regs.h b/drivers/dma/dw_dmac_regs.h
    index 5915743..47138b1 100644
    --- a/drivers/dma/dw_dmac_regs.h
    +++ b/drivers/dma/dw_dmac_regs.h
    @@ -138,6 +138,7 @@ struct dw_dma_chan {
    void __iomem *ch_regs;
    u8 mask;
    u8 priority;
    + bool paused;

    spinlock_t lock;
    unsigned long lflags;
    --
    1.7.2.2


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