From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tony Lindgren Subject: Re: [PATCH v2 1/2] dmaengine: cppi41: Fix list not empty warning on runtime suspend Date: Thu, 12 Jan 2017 09:09:00 -0800 Message-ID: <20170112170900.GG2630@atomide.com> References: <20170109170337.6957-1-abailon@baylibre.com> <20170109170337.6957-2-abailon@baylibre.com> <20170109183416.GJ2630@atomide.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20170109183416.GJ2630-4v6yS6AI5VpBDgjK7y7TUQ@public.gmane.org> Sender: linux-usb-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Alexandre Bailon Cc: vinod.koul-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org, dmaengine-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-usb-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, nsekhar-l0cyMroinI0@public.gmane.org, khilman-rdvid1DuHRBWk0Htik3J/w@public.gmane.org, ptitiano-rdvid1DuHRBWk0Htik3J/w@public.gmane.org, linux-omap-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, andy.shevchenko-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org List-Id: linux-omap@vger.kernel.org * Tony Lindgren [170109 10:35]: > Hi, > > * Alexandre Bailon [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 > > --- > > 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); -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html