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SubjectRe: [PATCH v3 1/2] dmaengine: qcom-bam-dma: Add pm_runtime support
On Wed, May 04, 2016 at 02:12:02PM +0530, Pramod Gurav wrote:
> Adds pm_runtime support for BAM DMA so that clock
> is enabled only when there is a transaction going on to help
> save power.
>
> Signed-off-by: Pramod Gurav <pramod.gurav@linaro.org>
> ---
> Changes in v2:
> - Handled return values of pm_runtime_get_sync to return error
> - Rework remove function
>
> drivers/dma/qcom/bam_dma.c | 98 +++++++++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 97 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/dma/qcom/bam_dma.c b/drivers/dma/qcom/bam_dma.c
> index 5b427c4..da64511 100644
> --- a/drivers/dma/qcom/bam_dma.c
> +++ b/drivers/dma/qcom/bam_dma.c
> @@ -48,6 +48,7 @@
> #include <linux/of_dma.h>
> #include <linux/clk.h>
> #include <linux/dmaengine.h>
> +#include <linux/pm_runtime.h>
>
> #include "../dmaengine.h"
> #include "../virt-dma.h"
> @@ -58,6 +59,8 @@ struct bam_desc_hw {
> u16 flags;
> };
>
> +#define BAM_DMA_AUTOSUSPEND_DELAY 100
> +
> #define DESC_FLAG_INT BIT(15)
> #define DESC_FLAG_EOT BIT(14)
> #define DESC_FLAG_EOB BIT(13)
> @@ -528,11 +531,14 @@ static void bam_free_chan(struct dma_chan *chan)
> u32 val;
> unsigned long flags;
>
> + if (pm_runtime_get_sync(bdev->dev))
> + return;
> +
> vchan_free_chan_resources(to_virt_chan(chan));
>
> if (bchan->curr_txd) {
> dev_err(bchan->bdev->dev, "Cannot free busy channel\n");
> - return;
> + goto err;
> }
>
> spin_lock_irqsave(&bchan->vc.lock, flags);
> @@ -550,6 +556,10 @@ static void bam_free_chan(struct dma_chan *chan)
>
> /* disable irq */
> writel_relaxed(0, bam_addr(bdev, bchan->id, BAM_P_IRQ_EN));
> +
> +err:
> + pm_runtime_mark_last_busy(bdev->dev);
> + pm_runtime_put_autosuspend(bdev->dev);
> }
>
> /**
> @@ -695,11 +705,18 @@ static int bam_pause(struct dma_chan *chan)
> struct bam_chan *bchan = to_bam_chan(chan);
> struct bam_device *bdev = bchan->bdev;
> unsigned long flag;
> + int ret;
> +
> + ret = pm_runtime_get_sync(bdev->dev);
> + if (ret)
> + return ret;
>
> spin_lock_irqsave(&bchan->vc.lock, flag);
> writel_relaxed(1, bam_addr(bdev, bchan->id, BAM_P_HALT));
> bchan->paused = 1;
> spin_unlock_irqrestore(&bchan->vc.lock, flag);
> + pm_runtime_mark_last_busy(bdev->dev);
> + pm_runtime_put_autosuspend(bdev->dev);
>
> return 0;
> }
> @@ -714,11 +731,17 @@ static int bam_resume(struct dma_chan *chan)
> struct bam_chan *bchan = to_bam_chan(chan);
> struct bam_device *bdev = bchan->bdev;
> unsigned long flag;
> + int ret;
>
> + ret = pm_runtime_get_sync(bdev->dev);
> + if (ret)
> + return ret;
> spin_lock_irqsave(&bchan->vc.lock, flag);
> writel_relaxed(0, bam_addr(bdev, bchan->id, BAM_P_HALT));
> bchan->paused = 0;
> spin_unlock_irqrestore(&bchan->vc.lock, flag);
> + pm_runtime_mark_last_busy(bdev->dev);
> + pm_runtime_put_autosuspend(bdev->dev);
>
> return 0;
> }
> @@ -967,6 +990,9 @@ static void dma_tasklet(unsigned long data)
> bam_start_dma(bchan);
> spin_unlock_irqrestore(&bchan->vc.lock, flags);
> }
> +
> + pm_runtime_mark_last_busy(bdev->dev);
> + pm_runtime_put_autosuspend(bdev->dev);

I think we shouldnt be doing this unless we have nothing else on the lists.
Perhaps the bam_start_dma function can be the place where we decide to do the
get_sync and the autosuspend.

> }
>
> /**
> @@ -978,8 +1004,13 @@ static void dma_tasklet(unsigned long data)
> static void bam_issue_pending(struct dma_chan *chan)
> {
> struct bam_chan *bchan = to_bam_chan(chan);
> + struct bam_device *bdev = bchan->bdev;
> unsigned long flags;
>
> + if (pm_runtime_status_suspended(bdev->dev))
> + if (pm_runtime_get_sync(bdev->dev))
> + return;
> +

We should only do this if our lists were empty before. That means we weren't
doing any work.

> spin_lock_irqsave(&bchan->vc.lock, flags);
>
> /* if work pending and idle, start a transaction */
> @@ -1210,6 +1241,13 @@ static int bam_dma_probe(struct platform_device *pdev)
> if (ret)
> goto err_unregister_dma;
>
> + pm_runtime_irq_safe(&pdev->dev);

I wonder if this is really necessary. We don't directly access any pm runtime
calls from irq context.

> + pm_runtime_set_autosuspend_delay(&pdev->dev, BAM_DMA_AUTOSUSPEND_DELAY);
> + pm_runtime_use_autosuspend(&pdev->dev);

If we use the autosuspend, we have to make sure we never pull the rug out from
under the device if there is a pending transaction. So that being the case, I
think if we only do the autosuspend after the lists are empty, we are going to
be ok. But we can't be allowing autosuspend while the controller is working.


> + pm_runtime_mark_last_busy(&pdev->dev);
> + pm_runtime_set_active(&pdev->dev);
> + pm_runtime_enable(&pdev->dev);
> +
> return 0;
>
> err_unregister_dma:
> @@ -1230,6 +1268,8 @@ static int bam_dma_remove(struct platform_device *pdev)
> struct bam_device *bdev = platform_get_drvdata(pdev);
> u32 i;
>
> + pm_runtime_force_suspend(&pdev->dev);
> +
> of_dma_controller_free(pdev->dev.of_node);
> dma_async_device_unregister(&bdev->common);
>
> @@ -1257,11 +1297,67 @@ static int bam_dma_remove(struct platform_device *pdev)
> return 0;
> }
>
> +static int bam_dma_runtime_suspend(struct device *dev)
> +{
> + struct bam_device *bdev = dev_get_drvdata(dev);
> +
> + clk_disable(bdev->bamclk);
> +
> + return 0;
> +}
> +
> +static int bam_dma_runtime_resume(struct device *dev)
> +{
> + struct bam_device *bdev = dev_get_drvdata(dev);
> + int ret;
> +
> + ret = clk_enable(bdev->bamclk);
> + if (ret < 0) {
> + dev_err(dev, "clk_enable failed: %d\n", ret);
> + return ret;
> + }
> +
> + return 0;
> +}
> +#ifdef CONFIG_PM_SLEEP
> +static int bam_dma_suspend(struct device *dev)
> +{
> + struct bam_device *bdev = dev_get_drvdata(dev);
> +
> + pm_runtime_force_suspend(dev);
> +
> + clk_unprepare(bdev->bamclk);
> +
> + return 0;
> +}
> +
> +static int bam_dma_resume(struct device *dev)
> +{
> + struct bam_device *bdev = dev_get_drvdata(dev);
> + int ret;
> +
> + ret = clk_prepare(bdev->bamclk);
> + if (ret)
> + return ret;
> +
> + pm_runtime_force_resume(dev);
> +
> + return 0;
> +}
> +#endif
> +
> +static const struct dev_pm_ops bam_dma_pm_ops = {
> + SET_LATE_SYSTEM_SLEEP_PM_OPS(bam_dma_suspend, bam_dma_resume)
> + SET_RUNTIME_PM_OPS(bam_dma_runtime_suspend, bam_dma_runtime_resume,
> + NULL)
> +};
> +
> static struct platform_driver bam_dma_driver = {
> .probe = bam_dma_probe,
> .remove = bam_dma_remove,
> .driver = {
> .name = "bam-dma-engine",
> + .pm = &bam_dma_pm_ops,
> .of_match_table = bam_of_match,
> },
> };
> --
> 1.8.2.1
>
> --
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