dmaengine: of_dma: Support for DMA routers

DMA routers are transparent devices used to mux DMA requests from
peripherals to DMA controllers. They are used when the SoC integrates more
devices with DMA requests then their controller can handle.
DRA7x is one example of such SoC, where the sDMA can hanlde 128 DMA request
lines, but in SoC level it has 205 DMA requests.

The of_dma_router will be registered as of_dma_controller with special
xlate function and additional parameters. The driver for the router is
responsible to craft the dma_spec (in the of_dma_route_allocate callback)
which can be used to requests a DMA channel from the real DMA controller.
This way the router can be transparent for the system while remaining generic
enough to be used in different environments.

Signed-off-by: Peter Ujfalusi <[email protected]>
Signed-off-by: Vinod Koul <[email protected]>

Author: Peter Ujfalusi

Documentation/devicetree/bindings/dma/dma.txt

@@ -31,6 +31,34 @@ Example:
 		dma-requests = <127>;
 	};
 
+* DMA router
+
+DMA routers are transparent IP blocks used to route DMA request lines from
+devices to the DMA controller. Some SoCs (like TI DRA7x) have more peripherals
+integrated with DMA requests than what the DMA controller can handle directly.
+
+Required property:
+- dma-masters:		phandle of the DMA controller or list of phandles for
+			the DMA controllers the router can direct the signal to.
+- #dma-cells: 		Must be at least 1. Used to provide DMA router specific
+			information. See DMA client binding below for more
+			details.
+
+Optional properties:
+- dma-requests: 	Number of incoming request lines the router can handle.
+- In the node pointed by the dma-masters:
+	- dma-requests:	The router driver might need to look for this in order
+			to configure the routing.
+
+Example:
+	sdma_xbar: dma-router@4a002b78 {
+		compatible = "ti,dra7-dma-crossbar";
+		reg = <0x4a002b78 0xfc>;
+		#dma-cells = <1>;
+		dma-requests = <205>;
+		ti,dma-safe-map = <0>;
+		dma-masters = <&sdma>;
+	};
 
 * DMA client
 

drivers/dma/dmaengine.c

@@ -267,6 +267,13 @@ static void dma_chan_put(struct dma_chan *chan)
 	/* This channel is not in use anymore, free it */
 	if (!chan->client_count && chan->device->device_free_chan_resources)
 		chan->device->device_free_chan_resources(chan);
+
+	/* If the channel is used via a DMA request router, free the mapping */
+	if (chan->router && chan->router->route_free) {
+		chan->router->route_free(chan->router->dev, chan->route_data);
+		chan->router = NULL;
+		chan->route_data = NULL;
+	}
 }
 
 enum dma_status dma_sync_wait(struct dma_chan *chan, dma_cookie_t cookie)

drivers/dma/of-dma.c

@@ -44,6 +44,50 @@ static struct of_dma *of_dma_find_controller(struct of_phandle_args *dma_spec)
 	return NULL;
 }
 
+/**
+ * of_dma_router_xlate - translation function for router devices
+ * @dma_spec:	pointer to DMA specifier as found in the device tree
+ * @of_dma:	pointer to DMA controller data (router information)
+ *
+ * The function creates new dma_spec to be passed to the router driver's
+ * of_dma_route_allocate() function to prepare a dma_spec which will be used
+ * to request channel from the real DMA controller.
+ */
+static struct dma_chan *of_dma_router_xlate(struct of_phandle_args *dma_spec,
+					    struct of_dma *ofdma)
+{
+	struct dma_chan		*chan;
+	struct of_dma		*ofdma_target;
+	struct of_phandle_args	dma_spec_target;
+	void			*route_data;
+
+	/* translate the request for the real DMA controller */
+	memcpy(&dma_spec_target, dma_spec, sizeof(dma_spec_target));
+	route_data = ofdma->of_dma_route_allocate(&dma_spec_target, ofdma);
+	if (IS_ERR(route_data))
+		return NULL;
+
+	ofdma_target = of_dma_find_controller(&dma_spec_target);
+	if (!ofdma_target)
+		return NULL;
+
+	chan = ofdma_target->of_dma_xlate(&dma_spec_target, ofdma_target);
+	if (chan) {
+		chan->router = ofdma->dma_router;
+		chan->route_data = route_data;
+	} else {
+		ofdma->dma_router->route_free(ofdma->dma_router->dev,
+					      route_data);
+	}
+
+	/*
+	 * Need to put the node back since the ofdma->of_dma_route_allocate
+	 * has taken it for generating the new, translated dma_spec
+	 */
+	of_node_put(dma_spec_target.np);
+	return chan;
+}
+
 /**
  * of_dma_controller_register - Register a DMA controller to DT DMA helpers
  * @np:			device node of DMA controller
@@ -109,6 +153,51 @@ void of_dma_controller_free(struct device_node *np)
 }
 EXPORT_SYMBOL_GPL(of_dma_controller_free);
 
+/**
+ * of_dma_router_register - Register a DMA router to DT DMA helpers as a
+ *			    controller
+ * @np:				device node of DMA router
+ * @of_dma_route_allocate:	setup function for the router which need to
+ *				modify the dma_spec for the DMA controller to
+ *				use and to set up the requested route.
+ * @dma_router:			pointer to dma_router structure to be used when
+ *				the route need to be free up.
+ *
+ * Returns 0 on success or appropriate errno value on error.
+ *
+ * Allocated memory should be freed with appropriate of_dma_controller_free()
+ * call.
+ */
+int of_dma_router_register(struct device_node *np,
+			   void *(*of_dma_route_allocate)
+			   (struct of_phandle_args *, struct of_dma *),
+			   struct dma_router *dma_router)
+{
+	struct of_dma	*ofdma;
+
+	if (!np || !of_dma_route_allocate || !dma_router) {
+		pr_err("%s: not enough information provided\n", __func__);
+		return -EINVAL;
+	}
+
+	ofdma = kzalloc(sizeof(*ofdma), GFP_KERNEL);
+	if (!ofdma)
+		return -ENOMEM;
+
+	ofdma->of_node = np;
+	ofdma->of_dma_xlate = of_dma_router_xlate;
+	ofdma->of_dma_route_allocate = of_dma_route_allocate;
+	ofdma->dma_router = dma_router;
+
+	/* Now queue of_dma controller structure in list */
+	mutex_lock(&of_dma_lock);
+	list_add_tail(&ofdma->of_dma_controllers, &of_dma_list);
+	mutex_unlock(&of_dma_lock);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(of_dma_router_register);
+
 /**
  * of_dma_match_channel - Check if a DMA specifier matches name
  * @np:		device node to look for DMA channels

include/linux/dmaengine.h

@@ -221,6 +221,16 @@ struct dma_chan_percpu {
 	unsigned long bytes_transferred;
 };
 
+/**
+ * struct dma_router - DMA router structure
+ * @dev: pointer to the DMA router device
+ * @route_free: function to be called when the route can be disconnected
+ */
+struct dma_router {
+	struct device *dev;
+	void (*route_free)(struct device *dev, void *route_data);
+};
+
 /**
  * struct dma_chan - devices supply DMA channels, clients use them
  * @device: ptr to the dma device who supplies this channel, always !%NULL
@@ -232,6 +242,8 @@ struct dma_chan_percpu {
  * @local: per-cpu pointer to a struct dma_chan_percpu
  * @client_count: how many clients are using this channel
  * @table_count: number of appearances in the mem-to-mem allocation table
+ * @router: pointer to the DMA router structure
+ * @route_data: channel specific data for the router
  * @private: private data for certain client-channel associations
  */
 struct dma_chan {
@@ -247,6 +259,11 @@ struct dma_chan {
 	struct dma_chan_percpu __percpu *local;
 	int client_count;
 	int table_count;
+
+	/* DMA router */
+	struct dma_router *router;
+	void *route_data;
+
 	void *private;
 };
 

include/linux/of_dma.h

@@ -23,6 +23,9 @@ struct of_dma {
 	struct device_node	*of_node;
 	struct dma_chan		*(*of_dma_xlate)
 				(struct of_phandle_args *, struct of_dma *);
+	void			*(*of_dma_route_allocate)
+				(struct of_phandle_args *, struct of_dma *);
+	struct dma_router	*dma_router;
 	void			*of_dma_data;
 };
 
@@ -37,12 +40,20 @@ extern int of_dma_controller_register(struct device_node *np,
 		(struct of_phandle_args *, struct of_dma *),
 		void *data);
 extern void of_dma_controller_free(struct device_node *np);
+
+extern int of_dma_router_register(struct device_node *np,
+		void *(*of_dma_route_allocate)
+		(struct of_phandle_args *, struct of_dma *),
+		struct dma_router *dma_router);
+#define of_dma_router_free of_dma_controller_free
+
 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_xlate_by_chan_id(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)
@@ -56,6 +67,16 @@ static inline void of_dma_controller_free(struct device_node *np)
 {
 }
 
+static inline int of_dma_router_register(struct device_node *np,
+		void *(*of_dma_route_allocate)
+		(struct of_phandle_args *, struct of_dma *),
+		struct dma_router *dma_router)
+{
+	return -ENODEV;
+}
+
+#define of_dma_router_free of_dma_controller_free
+
 static inline struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
 						     const char *name)
 {