On Mon, Oct 02, 2017 at 10:44:39AM +0100, Ed Blake wrote:
> Add suspend / resume handling using suspend_late and resume_early, and
> check that all channels are idle before suspending.
>
> DMA drivers should use suspend_late / resume_early to ensure that all
> DMA client devices are suspended before the DMA device itself, and that
> client devices are resumed after the DMA device. This avoids suspending
> the DMA device while transactions are still active.
>
> It is the responsibility of client drivers to terminate all DMA
> transactions in their suspend handlers, so there should be no active
> transactions by the time suspend_late is called.
>
> There's no need to save and restore registers for MDC during suspend /
> resume, as all transactions will be terminated as a result of the
> suspend, and all required registers are programmed anyway at the start
> of any new transactions following resume.
>
> Signed-off-by: Ed Blake <ed.blake@xxxxxxxxxxx>
> ---
> drivers/dma/img-mdc-dma.c | 36 ++++++++++++++++++++++++++++++++++++
> 1 file changed, 36 insertions(+)
>
> diff --git a/drivers/dma/img-mdc-dma.c b/drivers/dma/img-mdc-dma.c
> index 54db141..ca382c9 100644
> --- a/drivers/dma/img-mdc-dma.c
> +++ b/drivers/dma/img-mdc-dma.c
> @@ -1009,9 +1009,45 @@ static int mdc_dma_remove(struct platform_device *pdev)
> return 0;
> }
>
> +#ifdef CONFIG_PM_SLEEP
> +static int img_mdc_suspend_late(struct device *dev)
> +{
> + struct mdc_dma *mdma = dev_get_drvdata(dev);
> + int i;
> +
> + /* Check that all channels are idle */
> + for (i = 0; i < mdma->nr_channels; i++) {
> + struct mdc_chan *mchan = &mdma->channels[i];
> +
> + if (unlikely(mchan->desc))
> + return -EBUSY;
> + }
> +
> + clk_disable_unprepare(mdma->clk);
> +
> + return 0;
> +}
> +
> +static int img_mdc_resume_early(struct device *dev)
> +{
> + struct mdc_dma *mdma = dev_get_drvdata(dev);
> + int ret = 0;
> +
> + ret = clk_prepare_enable(mdma->clk);
this can be return clk_prepare_enable()
> +
> + return ret;
> +}
> +#endif /* CONFIG_PM_SLEEP */
> +
> +static const struct dev_pm_ops img_mdc_pm_ops = {
> + SET_LATE_SYSTEM_SLEEP_PM_OPS(img_mdc_suspend_late,
> + img_mdc_resume_early)
any reason for late ops?
> +};
> +
> static struct platform_driver mdc_dma_driver = {
> .driver = {
> .name = "img-mdc-dma",
> + .pm = &img_mdc_pm_ops,
> .of_match_table = of_match_ptr(mdc_dma_of_match),
> },
> .probe = mdc_dma_probe,
> --
> 1.9.1
>
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--
~Vinod
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