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SubjectRe: [PATCH] dmaengine: pl330: get rid of pm_runtime_irq_safe()
From
2015-04-10 8:57 GMT+02:00 Robert Baldyga <r.baldyga@samsung.com>:
> As using pm_runtime_irq_safe() causes power domain is always enabled,
> we want to get rid of it to reach better power efficiency. For this purpose
> we call pm_runtime_get()/pm_runtime_put() only in DMA channel allocate/free
> code. DMA channels are always requested and freed in non-atomic context,
> so we don't need pm_runtime_irq_safe().
>
> With pm_runtime_irq_safe() enabled the only action performed by
> pm_runtime_get()/pm_runtime_put() functions was enabling and disabling
> AHB clock, so now we do that manually to avoid using pm_runtime functions
> in atomic context.
>
> In result we manage AHB clock as we did before, plus we can disable power
> domain when nobody uses DMA controller.
>
> Signed-off-by: Robert Baldyga <r.baldyga@samsung.com>

Great job! Some comments below.

> ---
> drivers/dma/pl330.c | 57 ++++++++++++++++++++++++++++++++---------------------
> 1 file changed, 34 insertions(+), 23 deletions(-)
>
> diff --git a/drivers/dma/pl330.c b/drivers/dma/pl330.c
> index 0e1f567..5348ab9 100644
> --- a/drivers/dma/pl330.c
> +++ b/drivers/dma/pl330.c
> @@ -1969,6 +1969,7 @@ static inline void fill_queue(struct dma_pl330_chan *pch)
> static void pl330_tasklet(unsigned long data)
> {
> struct dma_pl330_chan *pch = (struct dma_pl330_chan *)data;
> + struct amba_device *pcdev = to_amba_device(pch->dmac->ddma.dev);
> struct dma_pl330_desc *desc, *_dt;
> unsigned long flags;
> bool power_down = false;
> @@ -2032,11 +2033,9 @@ static void pl330_tasklet(unsigned long data)
> }
> spin_unlock_irqrestore(&pch->lock, flags);
>
> - /* If work list empty, power down */
> - if (power_down) {
> - pm_runtime_mark_last_busy(pch->dmac->ddma.dev);
> - pm_runtime_put_autosuspend(pch->dmac->ddma.dev);
> - }
> + /* If work list empty, disable clock */
> + if (power_down)
> + amba_pclk_disable(pcdev);
> }
>
> bool pl330_filter(struct dma_chan *chan, void *param)
> @@ -2077,6 +2076,7 @@ static int pl330_alloc_chan_resources(struct dma_chan *chan)
> struct pl330_dmac *pl330 = pch->dmac;
> unsigned long flags;
>
> + pm_runtime_get_sync(pch->dmac->ddma.dev);
> spin_lock_irqsave(&pch->lock, flags);
>
> dma_cookie_init(chan);
> @@ -2165,10 +2165,15 @@ static int pl330_terminate_all(struct dma_chan *chan)
> int pl330_pause(struct dma_chan *chan)
> {
> struct dma_pl330_chan *pch = to_pchan(chan);
> + struct amba_device *pcdev = to_amba_device(pch->dmac->ddma.dev);
> struct pl330_dmac *pl330 = pch->dmac;
> unsigned long flags;
> + int ret;
> +
> + ret = amba_pclk_enable(pcdev);
> + if (ret < 0)
> + return ret;
>
> - pm_runtime_get_sync(pl330->ddma.dev);
> spin_lock_irqsave(&pch->lock, flags);
>
> spin_lock(&pl330->lock);
> @@ -2176,8 +2181,7 @@ int pl330_pause(struct dma_chan *chan)
> spin_unlock(&pl330->lock);
>
> spin_unlock_irqrestore(&pch->lock, flags);
> - pm_runtime_mark_last_busy(pl330->ddma.dev);
> - pm_runtime_put_autosuspend(pl330->ddma.dev);
> + amba_pclk_disable(pcdev);
>
> return 0;
> }
> @@ -2185,11 +2189,16 @@ int pl330_pause(struct dma_chan *chan)
> static void pl330_free_chan_resources(struct dma_chan *chan)
> {
> struct dma_pl330_chan *pch = to_pchan(chan);
> + struct amba_device *pcdev = to_amba_device(pch->dmac->ddma.dev);
> unsigned long flags;
> + int ret;
>
> tasklet_kill(&pch->task);
>
> - pm_runtime_get_sync(pch->dmac->ddma.dev);
> + ret = amba_pclk_enable(pcdev);
> + if (ret < 0)
> + return;
> +
> spin_lock_irqsave(&pch->lock, flags);
>
> pl330_release_channel(pch->thread);
> @@ -2199,6 +2208,7 @@ static void pl330_free_chan_resources(struct dma_chan *chan)
> list_splice_tail_init(&pch->work_list, &pch->dmac->desc_pool);
>
> spin_unlock_irqrestore(&pch->lock, flags);
> + amba_pclk_disable(pcdev);
> pm_runtime_mark_last_busy(pch->dmac->ddma.dev);
> pm_runtime_put_autosuspend(pch->dmac->ddma.dev);
> }
> @@ -2206,12 +2216,17 @@ static void pl330_free_chan_resources(struct dma_chan *chan)
> int pl330_get_current_xferred_count(struct dma_pl330_chan *pch,
> struct dma_pl330_desc *desc)
> {
> + struct amba_device *pcdev = to_amba_device(pch->dmac->ddma.dev);
> struct pl330_thread *thrd = pch->thread;
> struct pl330_dmac *pl330 = pch->dmac;
> void __iomem *regs = thrd->dmac->base;
> u32 val, addr;
> + int ret;
> +
> + ret = amba_pclk_enable(pcdev);
> + if (ret < 0)
> + return ret;
>
> - pm_runtime_get_sync(pl330->ddma.dev);
> val = addr = 0;
> if (desc->rqcfg.src_inc) {
> val = readl(regs + SA(thrd->id));
> @@ -2220,8 +2235,8 @@ int pl330_get_current_xferred_count(struct dma_pl330_chan *pch,
> val = readl(regs + DA(thrd->id));
> addr = desc->px.dst_addr;
> }
> - pm_runtime_mark_last_busy(pch->dmac->ddma.dev);
> - pm_runtime_put_autosuspend(pl330->ddma.dev);
> +
> + amba_pclk_disable(pcdev);
> return val - addr;
> }
>
> @@ -2276,17 +2291,21 @@ out:
> static void pl330_issue_pending(struct dma_chan *chan)
> {
> struct dma_pl330_chan *pch = to_pchan(chan);
> + struct amba_device *pcdev = to_amba_device(pch->dmac->ddma.dev);
> unsigned long flags;
> + int ret;
>
> spin_lock_irqsave(&pch->lock, flags);
> if (list_empty(&pch->work_list)) {
> /*
> * Warn on nothing pending. Empty submitted_list may
> - * break our pm_runtime usage counter as it is
> - * updated on work_list emptiness status.
> + * break our clock usage counter as it is updated on
> + * work_list emptiness status.
> */
> WARN_ON(list_empty(&pch->submitted_list));
> - pm_runtime_get_sync(pch->dmac->ddma.dev);
> + ret = amba_pclk_enable(pcdev);
> + if (ret < 0)
> + return;
> }
> list_splice_tail_init(&pch->submitted_list, &pch->work_list);
> spin_unlock_irqrestore(&pch->lock, flags);
> @@ -2723,10 +2742,6 @@ static int __maybe_unused pl330_suspend(struct device *dev)
>
> pm_runtime_disable(dev);
>
> - if (!pm_runtime_status_suspended(dev)) {
> - /* amba did not disable the clock */
> - amba_pclk_disable(pcdev);
> - }

What if system suspend happens when clock is enabled? I think it may
happen between issue_pending and tasklet execution. In such (rare)
case the clock won't be disabled but will be unprepared.

> amba_pclk_unprepare(pcdev);
>
> return 0;
> @@ -2741,9 +2756,6 @@ static int __maybe_unused pl330_resume(struct device *dev)
> if (ret)
> return ret;
>
> - if (!pm_runtime_status_suspended(dev))
> - ret = amba_pclk_enable(pcdev);
> -
> pm_runtime_enable(dev);
>
> return ret;
> @@ -2910,7 +2922,6 @@ pl330_probe(struct amba_device *adev, const struct amba_id *id)
> pcfg->data_buf_dep, pcfg->data_bus_width / 8, pcfg->num_chan,
> pcfg->num_peri, pcfg->num_events);
>
> - pm_runtime_irq_safe(&adev->dev);
> pm_runtime_use_autosuspend(&adev->dev);
> pm_runtime_set_autosuspend_delay(&adev->dev, PL330_AUTOSUSPEND_DELAY);

Any needs for updating also PL330_AUTOSUSPEND_DELAY? I set it to 20ms
to avoid too frequent suspend/resume. In your solution suspend happens
in different cases so maybe the time should longer?

Best regards,
Krzysztof


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