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SubjectRe: [PATCH v8 12/19] dmaengine: tegra-apb: Keep clock enabled only during of DMA transfer
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On 09/02/2020 16:33, 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 | 36 ++++++++++++++++++++++++-----------
> 1 file changed, 25 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/dma/tegra20-apb-dma.c b/drivers/dma/tegra20-apb-dma.c
> index 049e98ae1240..6e057a9f0e46 100644
> --- a/drivers/dma/tegra20-apb-dma.c
> +++ b/drivers/dma/tegra20-apb-dma.c
> @@ -569,6 +569,7 @@ 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;
> @@ -604,9 +605,14 @@ 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);
> }
>
> @@ -712,6 +718,7 @@ static void tegra_dma_issue_pending(struct dma_chan *dc)
> {
> struct tegra_dma_channel *tdc = to_tegra_dma_chan(dc);
> unsigned long flags;
> + int err;
>
> spin_lock_irqsave(&tdc->lock, flags);
> if (list_empty(&tdc->pending_sg_req)) {
> @@ -719,6 +726,12 @@ 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) {
> + dev_err(tdc2dev(tdc), "Failed to enable DMA\n");
> + goto end;
> + }
> +
> tdc_start_head_req(tdc);
>
> /* Continuous single mode: Configure next req */
> @@ -774,6 +787,8 @@ 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);
>
> @@ -1268,22 +1283,15 @@ 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;
> @@ -1316,7 +1324,6 @@ 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;
> }
> @@ -1416,6 +1423,11 @@ static int tegra_dma_probe(struct platform_device *pdev)
>
> spin_lock_init(&tdma->global_lock);
>
> + ret = clk_prepare(tdma->dma_clk);
> + if (ret)
> + return ret;
> +
> + pm_runtime_irq_safe(&pdev->dev);
> pm_runtime_enable(&pdev->dev);
>
> ret = pm_runtime_get_sync(&pdev->dev);
> @@ -1531,6 +1543,7 @@ static int tegra_dma_probe(struct platform_device *pdev)
>
> err_pm_disable:
> pm_runtime_disable(&pdev->dev);
> + clk_unprepare(tdma->dma_clk);
>
> return ret;
> }
> @@ -1541,6 +1554,7 @@ static int tegra_dma_remove(struct platform_device *pdev)
>
> dma_async_device_unregister(&tdma->dma_dev);
> pm_runtime_disable(&pdev->dev);
> + clk_unprepare(tdma->dma_clk);
>
> return 0;
> }
> @@ -1569,7 +1583,7 @@ static int tegra_dma_runtime_suspend(struct device *dev)
> TEGRA_APBDMA_CHAN_WCOUNT);
> }
>
> - clk_disable_unprepare(tdma->dma_clk);
> + clk_disable(tdma->dma_clk);
>
> return 0;
> }
> @@ -1580,7 +1594,7 @@ static int tegra_dma_runtime_resume(struct device *dev)
> unsigned int i;
> int ret;
>
> - ret = clk_prepare_enable(tdma->dma_clk);
> + ret = clk_enable(tdma->dma_clk);
> if (ret < 0) {
> dev_err(dev, "clk_enable failed: %d\n", ret);
> return ret;
>

Acked-by: Jon Hunter <jonathanh@nvidia.com>

Thanks!
Jon

--
nvpublic

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