linux-kernel - [PATCH 2/4] dmaengine: virt-dma: Add synchronization helper function

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Message-Id: <1445334391-12272-3-git-send-email-lars@metafoo.de>
Date:	Tue, 20 Oct 2015 11:46:29 +0200
From:	Lars-Peter Clausen <lars@...afoo.de>
To:	Vinod Koul <vinod.koul@...el.com>, Takashi Iwai <tiwai@...e.com>
Cc:	Dan Williams <dan.j.williams@...el.com>,
	Russell King <rmk+kernel@....linux.org.uk>,
	Laurent Pinchart <renesas@...asonboard.com>,
	Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>,
	Qiao Zhou <zhouqiao@...vell.com>,
	Shengjiu Wang <shengjiu.wang@...escale.com>,
	Matt Campbell <mcampbell@...tope.com>,
	Jonah Petri <jpetri@...tope.com>, dmaengine@...r.kernel.org,
	alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
	Lars-Peter Clausen <lars@...afoo.de>
Subject: [PATCH 2/4] dmaengine: virt-dma: Add synchronization helper function

Add a synchronize helper function for the virt-dma library. The function
makes sure that any scheduled descriptor complete callbacks have finished
running before the function returns.

This needs to be called by drivers using virt-dma in their
device_synchronize() callback. Depending on the driver additional
operations might be necessary in addition to calling vchan_synchronize() to
ensure proper synchronization.

Signed-off-by: Lars-Peter Clausen <lars@...afoo.de>
---
 drivers/dma/virt-dma.h | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/dma/virt-dma.h b/drivers/dma/virt-dma.h
index 181b9526..e93de76 100644
--- a/drivers/dma/virt-dma.h
+++ b/drivers/dma/virt-dma.h
@@ -151,4 +151,17 @@ static inline void vchan_free_chan_resources(struct virt_dma_chan *vc)
 	vchan_dma_desc_free_list(vc, &head);
 }
 
+/**
+ * vchan_synchronize() - synchronize callback execution to the current context
+ * @vc: virtual channel to synchronize
+ *
+ * Makes sure that all scheduled or active callbacks have finished running. For
+ * proper operation the caller has to ensure that no new callbacks are scheduled
+ * after the invocation of this function started.
+ */
+static inline void vchan_synchronize(struct virt_dma_chan *vc)
+{
+	tasklet_kill(&vc->task);
+}
+
 #endif
-- 
2.1.4

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