* Tony Lindgren <t...@atomide.com> [170109 10:35]:
> Hi,
>
> * Alexandre Bailon <abai...@baylibre.com> [170109 09:04]:
> > 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 <abai...@baylibre.com>
> > ---
> > 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) {
> > + /*
> > + * 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);
>
> What guarantees that the PM runtime state is really active few lines later?
>
> A safer approach might be to check the queue for new entries by in
> cppi41_runtime_resume() using "while (!list_empty())" instead of
> list_for_each_entry(). That releases the spinlock between each entry
> and rechecks the list.
>
> And instead of doing WARN_ON(!list_empty(&cdd->pending)) it seems we
> should run the queue also on cppi41_runtime_suspend()?
Hmm so I started seeing these issues too with Linux next just plugging
in USB cable on bbb while configured as a USB peripheral :)
Below is what seems to fix issues for me, not seeing any more warnings
either.
Care to give it a try with your USB headset?
Regards,
Tony
8< --------------------------
diff --git a/drivers/dma/cppi41.c b/drivers/dma/cppi41.c
--- a/drivers/dma/cppi41.c
+++ b/drivers/dma/cppi41.c
@@ -153,6 +153,8 @@ struct cppi41_dd {
/* context for suspend/resume */
unsigned int dma_tdfdq;
+
+ bool active;
};
#define FIST_COMPLETION_QUEUE 93
@@ -320,7 +322,8 @@ static irqreturn_t cppi41_irq(int irq, void *data)
int error;
error = pm_runtime_get(cdd->ddev.dev);
- if (error < 0)
+ if (((error != -EINPROGRESS) && error < 0) ||
+ !cdd->active)
dev_err(cdd->ddev.dev, "%s pm runtime get:
%i\n",
__func__, error);
@@ -482,7 +485,7 @@ static void cppi41_dma_issue_pending(struct dma_chan *chan)
return;
}
- if (likely(pm_runtime_active(cdd->ddev.dev)))
+ if (likely(cdd->active))
push_desc_queue(c);
else
pending_desc(c);
@@ -1151,6 +1154,7 @@ static int __maybe_unused cppi41_runtime_suspend(struct
device *dev)
{
struct cppi41_dd *cdd = dev_get_drvdata(dev);
+ cdd->active = false;
WARN_ON(!list_empty(&cdd->pending));
return 0;
@@ -1159,13 +1163,20 @@ static int __maybe_unused cppi41_runtime_suspend(struct
device *dev)
static int __maybe_unused cppi41_runtime_resume(struct device *dev)
{
struct cppi41_dd *cdd = dev_get_drvdata(dev);
- struct cppi41_channel *c, *_c;
+ struct cppi41_channel *c;
unsigned long flags;
+ cdd->active = true;
+
spin_lock_irqsave(&cdd->lock, flags);
- list_for_each_entry_safe(c, _c, &cdd->pending, node) {
- push_desc_queue(c);
+ while (!list_empty(&cdd->pending)) {
+ c = list_first_entry(&cdd->pending,
+ struct cppi41_channel,
+ node);
list_del(&c->node);
+ spin_unlock_irqrestore(&cdd->lock, flags);
+ push_desc_queue(c);
+ spin_lock_irqsave(&cdd->lock, flags);
}
spin_unlock_irqrestore(&cdd->lock, flags);
--
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