Re: [PATCH V5 2/9] dmaengine: bcm2835-dma: add suspend/resume pm support

[Vinod Koul <vkoul@kernel.org>]

On 25-10-24, 12:36, Stefan Wahren wrote:
> bcm2835-dma provides the service to others, so it should
> suspend late and resume early.
> 
> Signed-off-by: Stefan Wahren <wahrenst@gmx.net>
> ---
>  drivers/dma/bcm2835-dma.c | 30 ++++++++++++++++++++++++++++++
>  1 file changed, 30 insertions(+)
> 
> diff --git a/drivers/dma/bcm2835-dma.c b/drivers/dma/bcm2835-dma.c
> index e1b92b4d7b05..647dda9f3376 100644
> --- a/drivers/dma/bcm2835-dma.c
> +++ b/drivers/dma/bcm2835-dma.c
> @@ -875,6 +875,35 @@ static struct dma_chan *bcm2835_dma_xlate(struct of_phandle_args *spec,
>  	return chan;
>  }
> 
> +static int bcm2835_dma_suspend_late(struct device *dev)
> +{
> +	struct bcm2835_dmadev *od = dev_get_drvdata(dev);
> +	struct bcm2835_chan *c, *next;
> +
> +	list_for_each_entry_safe(c, next, &od->ddev.channels,
> +				 vc.chan.device_node) {
> +		void __iomem *chan_base = c->chan_base;
> +
> +		if (readl(chan_base + BCM2835_DMA_ADDR)) {
> +			dev_warn(dev, "Suspend is prevented by chan %d\n",
> +				 c->ch);
> +			return -EBUSY;
> +		}

Can you help understand how this helps by logging... we are not adding
anything except checking this and resume is NOP as well!

> +	}
> +
> +	return 0;
> +}
> +
> +static int bcm2835_dma_resume_early(struct device *dev)
> +{
> +	return 0;
> +}
> +
> +static const struct dev_pm_ops bcm2835_dma_pm_ops = {
> +	SET_LATE_SYSTEM_SLEEP_PM_OPS(bcm2835_dma_suspend_late,
> +				     bcm2835_dma_resume_early)
> +};
> +
>  static int bcm2835_dma_probe(struct platform_device *pdev)
>  {
>  	struct bcm2835_dmadev *od;
> @@ -1033,6 +1062,7 @@ static struct platform_driver bcm2835_dma_driver = {
>  	.driver = {
>  		.name = "bcm2835-dma",
>  		.of_match_table = of_match_ptr(bcm2835_dma_of_match),
> +		.pm = pm_ptr(&bcm2835_dma_pm_ops),
>  	},
>  };
> 
> --
> 2.34.1

-- 
~Vinod