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    SubjectRe: [PATCH v7 14/19] dmaengine: tegra-apb: Keep clock enabled only during of DMA transfer
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    On 02/02/2020 22:28, Dmitry Osipenko wrote:
    > It's a bit impractical to enable hardware's clock at the time of DMA
    > channel's allocation because most of DMA client drivers allocate DMA
    > channel at the time of the driver's probing, and thus, DMA clock is kept
    > always-enabled in practice, defeating the whole purpose of runtime PM.
    >
    > Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
    > ---
    > drivers/dma/tegra20-apb-dma.c | 35 ++++++++++++++++++++++++-----------
    > 1 file changed, 24 insertions(+), 11 deletions(-)
    What about something like ...

    diff --git a/drivers/dma/tegra20-apb-dma.c b/drivers/dma/tegra20-apb-dma.c
    index 22b88ccff05d..d60532f19a43 100644
    --- a/drivers/dma/tegra20-apb-dma.c
    +++ b/drivers/dma/tegra20-apb-dma.c
    @@ -570,6 +570,7 @@ static bool handle_continuous_head_request(struct tegra_dma_channel *tdc,
    if (list_empty(&tdc->pending_sg_req)) {
    dev_err(tdc2dev(tdc), "DMA is running without req\n");
    tegra_dma_stop(tdc);
    + pm_runtime_put(tdc->tdma->dev);
    return false;
    }

    @@ -581,6 +582,7 @@ static bool handle_continuous_head_request(struct tegra_dma_channel *tdc,
    hsgreq = list_first_entry(&tdc->pending_sg_req, typeof(*hsgreq), node);
    if (!hsgreq->configured) {
    tegra_dma_stop(tdc);
    + pm_runtime_put(tdc->tdma->dev);
    dev_err(tdc2dev(tdc), "Error in DMA transfer, aborting DMA\n");
    tegra_dma_abort_all(tdc);
    return false;
    @@ -616,9 +618,14 @@ static void handle_once_dma_done(struct tegra_dma_channel *tdc,
    list_add_tail(&sgreq->node, &tdc->free_sg_req);

    /* Do not start DMA if it is going to be terminate */
    - if (to_terminate || list_empty(&tdc->pending_sg_req))
    + if (to_terminate)
    return;

    + if (list_empty(&tdc->pending_sg_req)) {
    + pm_runtime_put(tdc->tdma->dev);
    + return;
    + }
    +
    tdc_start_head_req(tdc);
    }

    @@ -731,6 +738,10 @@ static void tegra_dma_issue_pending(struct dma_chan *dc)
    goto end;
    }
    if (!tdc->busy) {
    + err = pm_runtime_get_sync(tdc->tdma->dev);
    + if (err < 0)
    + return err;
    +
    tdc_start_head_req(tdc);

    /* Continuous single mode: Configure next req */
    @@ -786,6 +797,8 @@ static int tegra_dma_terminate_all(struct dma_chan *dc)
    }
    tegra_dma_resume(tdc);

    + pm_runtime_put(tdc->tdma->dev);
    +
    skip_dma_stop:
    tegra_dma_abort_all(tdc);

    @@ -1280,22 +1293,15 @@ tegra_dma_prep_dma_cyclic(struct dma_chan *dc, dma_addr_t buf_addr,
    static int tegra_dma_alloc_chan_resources(struct dma_chan *dc)
    {
    struct tegra_dma_channel *tdc = to_tegra_dma_chan(dc);
    - struct tegra_dma *tdma = tdc->tdma;
    - int ret;

    dma_cookie_init(&tdc->dma_chan);

    - ret = pm_runtime_get_sync(tdma->dev);
    - if (ret < 0)
    - return ret;
    -
    return 0;
    }

    static void tegra_dma_free_chan_resources(struct dma_chan *dc)
    {
    struct tegra_dma_channel *tdc = to_tegra_dma_chan(dc);
    - struct tegra_dma *tdma = tdc->tdma;
    struct tegra_dma_desc *dma_desc;
    struct tegra_dma_sg_req *sg_req;
    struct list_head dma_desc_list;
    @@ -1328,7 +1334,6 @@ static void tegra_dma_free_chan_resources(struct dma_chan *dc)
    list_del(&sg_req->node);
    kfree(sg_req);
    }
    - pm_runtime_put(tdma->dev);

    tdc->slave_id = TEGRA_APBDMA_SLAVE_ID_INVALID;
    }
    --
    nvpublic

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