dma: add common of_dma_slave_xlate()

Commit Message

Stephen Warren Nov. 25, 2013, 9:48 p.m. UTC

From: Stephen Warren <[e-mail]>

mmp_pdma.c implements a custom of_xlate() function that is 95% identical
to what Tegra will need. Create a function to implement the common part,
so everyone doesn't just cut/paste the implementation.

Cc: Dan Williams <[e-mail]>
Cc: Vinod Koul <[e-mail]>
Cc: [e-mail]
Signed-off-by: Stephen Warren <[e-mail]>
---
This patch is a dependency for a series that reworks many of the Tegra
drivers.

As such, it needs to go into a topic branch on its own, based directly
on 3.13-rc1. If the DMA maintainers ack the patches I'm happy to create
this topic branch myself and send a pull request to the DMA tree. Or the
patches can be applied to a topic branch by the DMA maintainers and I
will merge their topic branch into the Tegra rework branch that I
mentioned.

Note that this patch is independant from the "dma: add channel request
API that supports deferred probe" which I just sent, so it could
(should?) be a different topic branch.
---
 drivers/dma/of-dma.c   | 43 +++++++++++++++++++++++++++++++++++++++++++
 include/linux/of_dma.h | 14 ++++++++++++++
 2 files changed, 57 insertions(+)

Patch

diff --git a/drivers/dma/of-dma.c b/drivers/dma/of-dma.c
index 0b88dd3d05f4..324ca538cd3b 100644
--- a/drivers/dma/of-dma.c
+++ b/drivers/dma/of-dma.c
@@ -215,3 +215,46 @@  struct dma_chan *of_dma_simple_xlate(struct of_phandle_args *dma_spec,
 			&dma_spec->args[0]);
 }
 EXPORT_SYMBOL_GPL(of_dma_simple_xlate);
+
+struct dma_chan *of_dma_slave_xlate(struct of_phandle_args *dma_spec,
+				    struct of_dma *ofdma)
+{
+	struct of_dma_slave_xlate_info *info = ofdma->of_dma_data;
+	struct dma_chan *candidate, *chan;
+	int ret;
+
+retry:
+	candidate = NULL;
+
+	/*
+	 * walk the list of channels registered with the current instance and
+	 * find one that is currently unused
+	 */
+	list_for_each_entry(chan, &info->device->channels, device_node)
+		if (chan->client_count == 0) {
+			candidate = chan;
+			break;
+		}
+
+	if (!candidate)
+		return NULL;
+
+	/*
+	 * dma_get_slave_channel will return NULL if we lost a race between
+	 * the lookup and the reservation
+	 */
+	chan = dma_get_slave_channel(candidate);
+	if (!chan)
+		goto retry;
+
+	if (info->post_alloc) {
+		ret = info->post_alloc(chan, dma_spec);
+		if (ret) {
+			dma_release_channel(chan);
+			return NULL;
+		}
+	}
+
+	return chan;
+}
+EXPORT_SYMBOL_GPL(of_dma_slave_xlate);
diff --git a/include/linux/of_dma.h b/include/linux/of_dma.h
index ae36298ba076..fb4187adc68b 100644
--- a/include/linux/of_dma.h
+++ b/include/linux/of_dma.h
@@ -31,6 +31,12 @@  struct of_dma_filter_info {
 	dma_filter_fn	filter_fn;
 };
 
+struct of_dma_slave_xlate_info {
+	struct dma_device *device;
+	int (*post_alloc)(struct dma_chan *chan,
+			  struct of_phandle_args *dma_spec);
+};
+
 #ifdef CONFIG_OF
 extern int of_dma_controller_register(struct device_node *np,
 		struct dma_chan *(*of_dma_xlate)
@@ -41,6 +47,8 @@  extern struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
 						     const char *name);
 extern struct dma_chan *of_dma_simple_xlate(struct of_phandle_args *dma_spec,
 		struct of_dma *ofdma);
+extern struct dma_chan *of_dma_slave_xlate(struct of_phandle_args *dma_spec,
+		struct of_dma *ofdma);
 #else
 static inline int of_dma_controller_register(struct device_node *np,
 		struct dma_chan *(*of_dma_xlate)
@@ -66,6 +74,12 @@  static inline struct dma_chan *of_dma_simple_xlate(struct of_phandle_args *dma_s
 	return NULL;
 }
 
+static inline struct dma_chan *of_dma_slave_xlate(struct of_phandle_args *dma_spec,
+		struct of_dma *ofdma)
+{
+	return NULL;
+}
+
 #endif
 
 #endif /* __LINUX_OF_DMA_H */