Subject: Re: [PATCH v2 8/8] DMA: Freescale: add suspend resume functions for DMA driver

From: Hongbo Zhang <[email-masked]>
Date: Thu, 10 Apr 2014 14:55:17 +0800

On 04/04/2014 11:27 AM, [email-masked] wrote:
> From: Hongbo Zhang <[email-masked]>
>
> This patch adds suspend resume functions for Freescale DMA driver.
> .prepare callback is used to stop further descriptors from being added into the
> pending queue, and also issue pending queues into execution if there is any.
> .suspend callback makes sure all the pending jobs are cleaned up and all the
> channels are idle, and save the mode registers.
> .resume callback re-initializes the channels by restore the mode registers.
>
> Signed-off-by: Hongbo Zhang <[email-masked]>
> ---
>   drivers/dma/fsldma.c |   99 ++++++++++++++++++++++++++++++++++++++++++++++++++
>   drivers/dma/fsldma.h |   16 ++++++++
>   2 files changed, 115 insertions(+)
>
> diff --git a/drivers/dma/fsldma.c b/drivers/dma/fsldma.c
> index c9bf54a..91482d2 100644
> --- a/drivers/dma/fsldma.c
> +++ b/drivers/dma/fsldma.c
> @@ -400,6 +400,14 @@ static dma_cookie_t fsl_dma_tx_submit(struct dma_async_tx_descriptor *tx)
>   
>   	spin_lock_bh(&chan->desc_lock);
>   
> +#ifdef CONFIG_PM
> +	if (unlikely(chan->pm_state != RUNNING)) {
> +		chan_dbg(chan, "cannot submit due to suspend\n");
> +		spin_unlock_bh(&chan->desc_lock);
> +		return -1;
> +	}
> +#endif
> +
>   	/*
>   	 * assign cookies to all of the software descriptors
>   	 * that make up this transaction
> @@ -1311,6 +1319,9 @@ static int fsl_dma_chan_probe(struct fsldma_device *fdev,
>   	INIT_LIST_HEAD(&chan->ld_running);
>   	INIT_LIST_HEAD(&chan->ld_completed);
>   	chan->idle = true;
> +#ifdef CONFIG_PM
> +	chan->pm_state = RUNNING;
> +#endif
>   
>   	chan->common.device = &fdev->common;
>   	dma_cookie_init(&chan->common);
> @@ -1450,6 +1461,91 @@ static int fsldma_of_remove(struct platform_device *op)
>   	return 0;
>   }
>   
> +#ifdef CONFIG_PM
> +static int fsldma_prepare(struct device *dev)
> +{
> +	struct platform_device *pdev = to_platform_device(dev);
> +	struct fsldma_device *fdev = platform_get_drvdata(pdev);
> +	struct fsldma_chan *chan;
> +	int i;
> +
> +	for (i = 0; i < FSL_DMA_MAX_CHANS_PER_DEVICE; i++) {
> +		chan = fdev->chan[i];
> +		if (!chan)
> +			continue;
> +
> +		spin_lock_bh(&chan->desc_lock);
> +		chan->pm_state = SUSPENDING;
> +		if (!list_empty(&chan->ld_pending))
> +			fsl_chan_xfer_ld_queue(chan);
> +		spin_unlock_bh(&chan->desc_lock);
> +	}
> +
> +	return 0;
> +}
> +
> +static int fsldma_suspend(struct device *dev)
> +{
> +	struct platform_device *pdev = to_platform_device(dev);
> +	struct fsldma_device *fdev = platform_get_drvdata(pdev);
> +	struct fsldma_chan *chan;
> +	int i;
> +
> +	for (i = 0; i < FSL_DMA_MAX_CHANS_PER_DEVICE; i++) {
> +		chan = fdev->chan[i];
> +		if (!chan)
> +			continue;
> +
> +		spin_lock_bh(&chan->desc_lock);
> +		if (!chan->idle)
> +			goto out;
> +		chan->regs_save.mr = DMA_IN(chan, &chan->regs->mr, 32);
> +		chan->pm_state = SUSPENDED;
> +		spin_unlock_bh(&chan->desc_lock);
> +	}
> +	return 0;
> +
> +out:
> +	for (; i >= 0; i--) {
> +		chan = fdev->chan[i];
> +		if (!chan)
> +			continue;

the pm_state should be restored too, e.g.
     chan->pm_state = RUNNING;
I will send new iteration for adding this.

> +		spin_unlock_bh(&chan->desc_lock);
> +	}
> +	return -EBUSY;
> +}
> +
> +static int fsldma_resume(struct device *dev)
> +{
> +	struct platform_device *pdev = to_platform_device(dev);
> +	struct fsldma_device *fdev = platform_get_drvdata(pdev);
> +	struct fsldma_chan *chan;
> +	u32 mode;
> +	int i;
> +
> +	for (i = 0; i < FSL_DMA_MAX_CHANS_PER_DEVICE; i++) {
> +		chan = fdev->chan[i];
> +		if (!chan)
> +			continue;
> +
> +		spin_lock_bh(&chan->desc_lock);
> +		mode = chan->regs_save.mr
> +			& ~FSL_DMA_MR_CS & ~FSL_DMA_MR_CC & ~FSL_DMA_MR_CA;
> +		DMA_OUT(chan, &chan->regs->mr, mode, 32);
> +		chan->pm_state = RUNNING;
> +		spin_unlock_bh(&chan->desc_lock);
> +	}
> +
> +	return 0;
> +}
> +
> +static const struct dev_pm_ops fsldma_pm_ops = {
> +	.prepare	= fsldma_prepare,
> +	.suspend	= fsldma_suspend,
> +	.resume		= fsldma_resume,
> +};
> +#endif
> +
>   static const struct of_device_id fsldma_of_ids[] = {
>   	{ .compatible = "fsl,elo3-dma", },
>   	{ .compatible = "fsl,eloplus-dma", },
> @@ -1462,6 +1558,9 @@ static struct platform_driver fsldma_of_driver = {
>   		.name = "fsl-elo-dma",
>   		.owner = THIS_MODULE,
>   		.of_match_table = fsldma_of_ids,
> +#ifdef CONFIG_PM
> +		.pm = &fsldma_pm_ops,
> +#endif
>   	},
>   	.probe = fsldma_of_probe,
>   	.remove = fsldma_of_remove,
> diff --git a/drivers/dma/fsldma.h b/drivers/dma/fsldma.h
> index ec19517..eecaf9e 100644
> --- a/drivers/dma/fsldma.h
> +++ b/drivers/dma/fsldma.h
> @@ -134,6 +134,18 @@ struct fsldma_device {
>   #define FSL_DMA_CHAN_PAUSE_EXT	0x00001000
>   #define FSL_DMA_CHAN_START_EXT	0x00002000
>   
> +#ifdef CONFIG_PM
> +struct fsldma_chan_regs_save {
> +	u32 mr;
> +};
> +
> +enum fsldma_pm_state {
> +	RUNNING = 0,
> +	SUSPENDING,
> +	SUSPENDED,
> +};
> +#endif
> +
>   struct fsldma_chan {
>   	char name[8];			/* Channel name */
>   	struct fsldma_chan_regs __iomem *regs;
> @@ -161,6 +173,10 @@ struct fsldma_chan {
>   	struct tasklet_struct tasklet;
>   	u32 feature;
>   	bool idle;			/* DMA controller is idle */
> +#ifdef CONFIG_PM
> +	struct fsldma_chan_regs_save regs_save;
> +	enum fsldma_pm_state pm_state;
> +#endif
>   
>   	void (*toggle_ext_pause)(struct fsldma_chan *fsl_chan, int enable);
>   	void (*toggle_ext_start)(struct fsldma_chan *fsl_chan, int enable);