Re: [RFC PATCH] dma: pl330: add Power Management support

[Michal Simek]

On 09/05/2014 05:06 PM, Krzysztof Kozlowski wrote:
> This patch adds both normal PM suspend/resume support and runtime PM
> support to pl330 DMA engine driver.
> 
> The runtime power management for pl330 DMA driver allows gating of AMBA
> clock (PDMA) in FSYS clock domain, when the device is not processing any
> requests. This is necessary to enter W-AFTR low power mode on Exynos3250.
> 
> The patch is based on previous work of Bartlomiej Zolnierkiewicz
> <b.zolnierkie@xxxxxxxxxxx>.
> 
> Signed-off-by: Krzysztof Kozlowski <k.kozlowski@xxxxxxxxxxx>
> ---
>  drivers/dma/pl330.c | 78 ++++++++++++++++++++++++++++++++++++++++++++++++++---
>  1 file changed, 74 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/dma/pl330.c b/drivers/dma/pl330.c
> index 66e89f04504c..bdc6ff8ee2bf 100644
> --- a/drivers/dma/pl330.c
> +++ b/drivers/dma/pl330.c
> @@ -27,6 +27,7 @@
>  #include <linux/of.h>
>  #include <linux/of_dma.h>
>  #include <linux/err.h>
> +#include <linux/pm_runtime.h>
>  
>  #include "dmaengine.h"
>  #define PL330_MAX_CHAN		8
> @@ -1966,6 +1967,7 @@ static void pl330_tasklet(unsigned long data)
>  	struct dma_pl330_chan *pch = (struct dma_pl330_chan *)data;
>  	struct dma_pl330_desc *desc, *_dt;
>  	unsigned long flags;
> +	bool power_down = false;
>  
>  	spin_lock_irqsave(&pch->lock, flags);
>  
> @@ -1980,10 +1982,17 @@ static void pl330_tasklet(unsigned long data)
>  	/* Try to submit a req imm. next to the last completed cookie */
>  	fill_queue(pch);
>  
> -	/* Make sure the PL330 Channel thread is active */
> -	spin_lock(&pch->thread->dmac->lock);
> -	_start(pch->thread);
> -	spin_unlock(&pch->thread->dmac->lock);
> +	if (list_empty(&pch->work_list)) {
> +		spin_lock(&pch->thread->dmac->lock);
> +		_stop(pch->thread);
> +		spin_unlock(&pch->thread->dmac->lock);
> +		power_down = true;
> +	} else {
> +		/* Make sure the PL330 Channel thread is active */
> +		spin_lock(&pch->thread->dmac->lock);
> +		_start(pch->thread);
> +		spin_unlock(&pch->thread->dmac->lock);
> +	}
>  
>  	while (!list_empty(&pch->completed_list)) {
>  		dma_async_tx_callback callback;
> @@ -1998,6 +2007,12 @@ static void pl330_tasklet(unsigned long data)
>  		if (pch->cyclic) {
>  			desc->status = PREP;
>  			list_move_tail(&desc->node, &pch->work_list);
> +			if (power_down) {
> +				spin_lock(&pch->thread->dmac->lock);
> +				_start(pch->thread);
> +				spin_unlock(&pch->thread->dmac->lock);
> +				power_down = false;
> +			}
>  		} else {
>  			desc->status = FREE;
>  			list_move_tail(&desc->node, &pch->dmac->desc_pool);
> @@ -2012,6 +2027,10 @@ static void pl330_tasklet(unsigned long data)
>  		}
>  	}
>  	spin_unlock_irqrestore(&pch->lock, flags);
> +
> +	/* If work list empty, power down */
> +	if (power_down)
> +		pm_runtime_put(pch->dmac->ddma.dev);
>  }
>  
>  bool pl330_filter(struct dma_chan *chan, void *param)
> @@ -2077,10 +2096,12 @@ static int pl330_control(struct dma_chan *chan, enum dma_ctrl_cmd cmd, unsigned
>  	unsigned long flags;
>  	struct pl330_dmac *pl330 = pch->dmac;
>  	struct dma_slave_config *slave_config;
> +	bool power_down = false;
>  	LIST_HEAD(list);
>  
>  	switch (cmd) {
>  	case DMA_TERMINATE_ALL:
> +		pm_runtime_get_sync(pl330->ddma.dev);
>  		spin_lock_irqsave(&pch->lock, flags);
>  
>  		spin_lock(&pl330->lock);
> @@ -2107,10 +2128,18 @@ static int pl330_control(struct dma_chan *chan, enum dma_ctrl_cmd cmd, unsigned
>  			dma_cookie_complete(&desc->txd);
>  		}
>  
> +		if (!list_empty(&pch->work_list))
> +			power_down = true;
> +
>  		list_splice_tail_init(&pch->submitted_list, &pl330->desc_pool);
>  		list_splice_tail_init(&pch->work_list, &pl330->desc_pool);
>  		list_splice_tail_init(&pch->completed_list, &pl330->desc_pool);
>  		spin_unlock_irqrestore(&pch->lock, flags);
> +		pm_runtime_put(pl330->ddma.dev);
> +
> +		/* If work list empty, power down */
> +		if (power_down)
> +			pm_runtime_put(pl330->ddma.dev);
>  		break;
>  	case DMA_SLAVE_CONFIG:
>  		slave_config = (struct dma_slave_config *)arg;
> @@ -2146,6 +2175,7 @@ static void pl330_free_chan_resources(struct dma_chan *chan)
>  
>  	tasklet_kill(&pch->task);
>  
> +	pm_runtime_get_sync(pch->dmac->ddma.dev);
>  	spin_lock_irqsave(&pch->lock, flags);
>  
>  	pl330_release_channel(pch->thread);
> @@ -2155,6 +2185,7 @@ 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);
> +	pm_runtime_put(pch->dmac->ddma.dev);
>  }
>  
>  static enum dma_status
> @@ -2168,11 +2199,23 @@ static void pl330_issue_pending(struct dma_chan *chan)
>  {
>  	struct dma_pl330_chan *pch = to_pchan(chan);
>  	unsigned long flags;
> +	bool power_up;
>  
>  	spin_lock_irqsave(&pch->lock, flags);
> +	power_up = list_empty(&pch->work_list);
>  	list_splice_tail_init(&pch->submitted_list, &pch->work_list);
>  	spin_unlock_irqrestore(&pch->lock, flags);
>  
> +	if (power_up) {
> +		/*
> +		 * Warn on nothing pending. This may break our pm_runtime
> +		 * usage counter as it is updated on work_list emptiness
> +		 * status.
> +		 */
> +		WARN_ON(list_empty(&pch->work_list));
> +		pm_runtime_get_sync(pch->dmac->ddma.dev);
> +	}
> +
>  	pl330_tasklet((unsigned long)pch);
>  }
>  
> @@ -2205,6 +2248,7 @@ static dma_cookie_t pl330_tx_submit(struct dma_async_tx_descriptor *tx)
>  
>  	cookie = dma_cookie_assign(&last->txd);
>  	list_add_tail(&last->node, &pch->submitted_list);
> +

unrelated change.

>  	spin_unlock_irqrestore(&pch->lock, flags);
>  
>  	return cookie;
> @@ -2593,6 +2637,28 @@ static int pl330_dma_device_slave_caps(struct dma_chan *dchan,
>  	return 0;
>  }
>  
> +#ifdef CONFIG_PM_SLEEP

remove this line

> +static int pl330_suspend(struct device *dev)

__maybe_unused here

> +{
> +	struct amba_device *pcdev = to_amba_device(dev);
> +
> +	if (!pm_runtime_suspended(dev))
> +		amba_pclk_disable(pcdev);
> +	return 0;
> +}
> +
> +static int pl330_resume(struct device *dev)

__maybe_unused here

> +{
> +	struct amba_device *pcdev = to_amba_device(dev);
> +
> +	if (!pm_runtime_suspended(dev))
> +		return amba_pclk_enable(pcdev);
> +	return 0;
> +}
> +#endif

remove this line

> +
> +static SIMPLE_DEV_PM_OPS(pl330_pm, pl330_suspend, pl330_resume);

Everything is handle inside this macro and your functions are not calling
anything what it is not defined for both cases.

Thanks,
Michal

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