Re: [PATCH v2 1/2] dmaengine: cppi41: Fix list not empty warning on runtime suspend

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On 01/09/2017 11:03 AM, Alexandre Bailon wrote:
> Sometime, a transfer may not be queued due to a race between runtime pm
> and cppi41_dma_issue_pending().
> Sometime, cppi41_runtime_resume() may be interrupted right before to
> update device PM state to RESUMED.
> When it happens, if a new dma transfer is issued, because the device is not
> in active state, the descriptor will be added to the pendding list.
> But because the descriptors in the pendding list are only queued to cppi41
> on runtime resume, the descriptor will not be queued.
> On runtime suspend, the list is not empty, which is causing a warning.
> Queue the descriptor if the device is active or resuming.
> 
> Signed-off-by: Alexandre Bailon <abailon@xxxxxxxxxxxx>
> ---
>  drivers/dma/cppi41.c | 18 +++++++++++++++++-
>  1 file changed, 17 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/dma/cppi41.c b/drivers/dma/cppi41.c
> index d5ba43a..025fee4 100644
> --- a/drivers/dma/cppi41.c
> +++ b/drivers/dma/cppi41.c
> @@ -471,6 +471,8 @@ static void cppi41_dma_issue_pending(struct dma_chan *chan)
>  {
>  	struct cppi41_channel *c = to_cpp41_chan(chan);
>  	struct cppi41_dd *cdd = c->cdd;
> +	unsigned long flags;
> +	bool active;
>  	int error;
>  
>  	error = pm_runtime_get(cdd->ddev.dev);
> @@ -482,7 +484,21 @@ static void cppi41_dma_issue_pending(struct dma_chan *chan)
>  		return;
>  	}
>  
> -	if (likely(pm_runtime_active(cdd->ddev.dev)))
> +	active = pm_runtime_active(cdd->ddev.dev);
> +	if (!active) {

just curious, what does prevent from using pm_runtime_get_sync() here and in
cppi41_dma_issue_pending()?

> +		/*
> +		 * Runtime resume may be interrupted before runtime_status
> +		 * has been updated. Test if device has resumed.
> +		 */
> +		if (error == -EINPROGRESS) {
> +			spin_lock_irqsave(&cdd->lock, flags);
> +			if (list_empty(&cdd->pending))
> +				active = true;
> +			spin_unlock_irqrestore(&cdd->lock, flags);
> +		}
> +	}
> +
> +	if (likely(active))
>  		push_desc_queue(c);
>  	else
>  		pending_desc(c);
> 

-- 
regards,
-grygorii
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