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

Lars-Peter Clausen
2014-09-05T15:23:53Z

On 09/05/2014 05:06 PM, Krzysztof Kozlowski wrote:
[...]
> @@ -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);

Unfortunately this does not work. pm_runtime_get_sync() may sleep, where as
the issue_pending callback needs to be able to run from contexts in which
sleeping is not possible.

> + }
> +
> pl330_tasklet((unsigned long)pch);
> }
> …