linux-kernel - Re: [PATCH v12 5/6] dmaengine: pl330: Add PM sleep support

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Date:	Fri, 14 Nov 2014 14:31:17 +0100
From:	Ulf Hansson <ulf.hansson@...aro.org>
To:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
Cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
	Russell King <linux@....linux.org.uk>,
	Dan Williams <dan.j.williams@...el.com>,
	Vinod Koul <vinod.koul@...el.com>,
	Alan Stern <stern@...land.harvard.edu>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	dmaengine@...r.kernel.org, Kevin Hilman <khilman@...nel.org>,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Subject: Re: [PATCH v12 5/6] dmaengine: pl330: Add PM sleep support

On 14 November 2014 09:50, Krzysztof Kozlowski <k.kozlowski@...sung.com> wrote:
> Add system suspend/resume capabilities to the pl330 driver so the amba
> bus clock could be also unprepared to conserve energy.
>
> Signed-off-by: Krzysztof Kozlowski <k.kozlowski@...sung.com>
> ---
>  drivers/dma/pl330.c | 41 +++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 41 insertions(+)
>
> diff --git a/drivers/dma/pl330.c b/drivers/dma/pl330.c
> index c3bd3584f261..e499bb118f0a 100644
> --- a/drivers/dma/pl330.c
> +++ b/drivers/dma/pl330.c
> @@ -2627,6 +2627,46 @@ static int pl330_dma_device_slave_caps(struct dma_chan *dchan,
>         return 0;
>  }
>
> +/*
> + * Runtime PM callbacks are provided by amba/bus.c driver.
> + *
> + * It is assumed here that IRQ safe runtime PM is chosen in probe and amba
> + * bus driver will only disable/enable the clock in runtime PM callbacks.
> + */
> +static int __maybe_unused pl330_suspend(struct device *dev)
> +{
> +       struct amba_device *pcdev = to_amba_device(dev);
> +
> +       pm_runtime_disable(dev);
> +
> +       if (!pm_runtime_status_suspended(dev)) {
> +               /* amba did not disable the clock */
> +               amba_pclk_disable(pcdev);
> +       }
> +       amba_pclk_unprepare(pcdev);

I would also invoke pm_runtime_set_suspended() here, to reflect that's
the current runtime PM state of the device.

I guess I sounds like broken record :-), but using
pm_runtime_force_suspend() would help to prevent some code duplication
here.

Something like this:

pm_runtime_force_suspend()
if (pm_runtime_is_irq_safe())
   amba_pclk_unprepare(pcdev);


Kind regards
Uffe

> +
> +       return 0;
> +}
> +
> +static int __maybe_unused pl330_resume(struct device *dev)
> +{
> +       struct amba_device *pcdev = to_amba_device(dev);
> +       int ret;
> +
> +       ret = amba_pclk_prepare(pcdev);
> +       if (ret)
> +               return ret;
> +
> +       if (!pm_runtime_status_suspended(dev))
> +               ret = amba_pclk_enable(pcdev);
> +
> +       pm_runtime_enable(dev);
> +
> +       return ret;
> +}
> +
> +static SIMPLE_DEV_PM_OPS(pl330_pm, pl330_suspend, pl330_resume);
> +
>  static int
>  pl330_probe(struct amba_device *adev, const struct amba_id *id)
>  {
> @@ -2853,6 +2893,7 @@ static struct amba_driver pl330_driver = {
>         .drv = {
>                 .owner = THIS_MODULE,
>                 .name = "dma-pl330",
> +               .pm = &pl330_pm,
>         },
>         .id_table = pl330_ids,
>         .probe = pl330_probe,
> --
> 1.9.1
--
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