[RFC PATCH 1/2] of: Add generic device tree DMA helpers

[b-cousson@ti.com (Cousson, Benoit)]

Add some basic helpers to retrieve a DMA controller device_node
and the DMA request line number.

For legacy reason another API will export the DMA request number
into a Linux resource of type IORESOURCE_DMA.
This API is usable only on system with an unique DMA controller.

Signed-off-by: Benoit Cousson <b-cousson@ti.com>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: Rob Herring <rob.herring@calxeda.com>
---
 Documentation/devicetree/bindings/dma/dma.txt |   44 +++++++++
 drivers/of/Kconfig                            |    5 +
 drivers/of/Makefile                           |    1 +
 drivers/of/dma.c                              |  130 +++++++++++++++++++++++++
 include/linux/of_dma.h                        |   49 +++++++++
 5 files changed, 229 insertions(+), 0 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/dma/dma.txt
 create mode 100644 drivers/of/dma.c
 create mode 100644 include/linux/of_dma.h

diff --git a/Documentation/devicetree/bindings/dma/dma.txt b/Documentation/devicetree/bindings/dma/dma.txt
new file mode 100644
index 0000000..7f2a301
--- /dev/null
+++ b/Documentation/devicetree/bindings/dma/dma.txt
@@ -0,0 +1,44 @@
+* Generic DMA Controller and DMA request bindings
+
+Generic binding to provide a way for a driver to retrieve the
+DMA request line that goes from an IP to a DMA controller.
+
+
+* DMA controller
+
+Required properties:
+    - dma-controller: Mark the device as a DMA controller
+    - #dma-cells: Number of cell for each DMA line, must be one.
+
+
+Example:
+
+	sdma: dma-controller at 48000000 {
+		compatible = "ti,sdma-omap4"
+		reg = <0x48000000 0x1000>;
+		interrupts = <12>;
+        dma-controller;
+		#dma-cells = <1>;
+	};
+
+
+
+* DMA client
+
+Client drivers should specify the DMA request numbers using a phandle to
+the controller + the DMA request number on that controller.
+
+Required properties:
+    - dma-request: List of pair phandle + dma-request per line
+    - dma-request-names: list of strings in the same order as the dma-request
+      in the dma-request property.
+
+
+Example:
+
+    i2c1: i2c at 1 {
+        ...
+        dma-request = <&sdma 2 &sdma 3>;
+        dma-request-names = "tx", "rx";
+        ...
+    };
diff --git a/drivers/of/Kconfig b/drivers/of/Kconfig
index 268163d..7d1f06b 100644
--- a/drivers/of/Kconfig
+++ b/drivers/of/Kconfig
@@ -90,4 +90,9 @@ config OF_PCI_IRQ
 	help
 	  OpenFirmware PCI IRQ routing helpers
 
+config OF_DMA
+	def_bool y
+	help
+	  Device Tree DMA routing helpers
+
 endmenu # OF
diff --git a/drivers/of/Makefile b/drivers/of/Makefile
index a73f5a5..d08443b 100644
--- a/drivers/of/Makefile
+++ b/drivers/of/Makefile
@@ -12,3 +12,4 @@ obj-$(CONFIG_OF_SELFTEST) += selftest.o
 obj-$(CONFIG_OF_MDIO)	+= of_mdio.o
 obj-$(CONFIG_OF_PCI)	+= of_pci.o
 obj-$(CONFIG_OF_PCI_IRQ)  += of_pci_irq.o
+obj-$(CONFIG_OF_DMA)  += dma.o
diff --git a/drivers/of/dma.c b/drivers/of/dma.c
new file mode 100644
index 0000000..d4927e2
--- /dev/null
+++ b/drivers/of/dma.c
@@ -0,0 +1,130 @@
+/*
+ * Device tree helpers for DMA request / controller
+ *
+ * Based on of_gpio.c
+ *
+ * Copyright (C) 2012 Texas Instruments Incorporated - http://www.ti.com/
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_dma.h>
+
+/**
+ * of_get_dma_request() - Get a DMA request number and dma-controller node
+ * @np:		device node to get DMA request from
+ * @propname:	property name containing DMA specifier(s)
+ * @index:	index of the DMA request
+ * @ctrl_np:	a device_node pointer to fill in
+ *
+ * Returns DMA number along to the dma controller node, or one of the errno
+ * value on the error condition. If @ctrl_np is not NULL the function also
+ * fills in the DMA controller device_node pointer.
+ */
+int of_get_dma_request(struct device_node *np, int index,
+		       struct device_node **ctrl_np)
+{
+	int ret = -EINVAL;
+	struct of_phandle_args dma_spec;
+
+	ret = of_parse_phandle_with_args(np, "dma-request", "#dma-cells",
+					 index, &dma_spec);
+	if (ret) {
+		pr_debug("%s: can't parse dma property\n", __func__);
+		goto err0;
+	}
+
+	if (dma_spec.args_count > 0)
+		ret = dma_spec.args[0];
+
+	if (ctrl_np)
+		*ctrl_np = dma_spec.np;
+	else
+		of_node_put(dma_spec.np);
+
+err0:
+	pr_debug("%s exited with status %d\n", __func__, ret);
+	return ret;
+}
+EXPORT_SYMBOL(of_get_dma_request);
+
+/**
+ * of_dma_count - Count DMA requests for a device
+ * @np:		device node to count DMAs for
+ *
+ * The function returns the count of DMA requests specified for a node.
+ *
+ * Note that the empty DMA specifiers counts too. For example,
+ *
+ * dma-request = <0
+ *                &sdma 1
+ *                0
+ *                &sdma 3>;
+ *
+ * defines four DMAs (so this function will return 4), two of which
+ * are not specified.
+ */
+unsigned int of_dma_count(struct device_node *np)
+{
+	unsigned int cnt = 0;
+
+	do {
+		int ret;
+
+		ret = of_parse_phandle_with_args(np, "dma-request",
+						 "#dma-cells", cnt, NULL);
+		/* A hole in the dma-request = <> counts anyway. */
+		if (ret < 0 && ret != -EEXIST)
+			break;
+	} while (++cnt);
+
+	return cnt;
+}
+EXPORT_SYMBOL(of_dma_count);
+
+/**
+ * of_dma_to_resource - Decode a node's DMA and return it as a resource
+ * @dev: pointer to device tree node
+ * @index: zero-based index of the DMA request
+ * @r: pointer to resource structure to return result into.
+ *
+ * Using a resource to export a DMA request number to a driver should
+ * be used only for legacy purpose and on system when only one DMA controller
+ * is present.
+ * The proper and only scalable way is to use the native of_get_dma_request API
+ * in order retrieve both the DMA controller device node and the DMA request
+ * line for that controller.
+ */
+int of_dma_to_resource(struct device_node *dev, int index, struct resource *r)
+{
+	const char *name = NULL;
+	int dma;
+
+	if (!r)
+		return -EINVAL;
+
+	dma = of_get_dma_request(dev, index, NULL);
+	if (dma < 0)
+		return dma;
+
+	/*
+	 * Get optional "dma-request-names" property to add a name
+	 * to the resource.
+	 */
+	of_property_read_string_index(dev, "dma-request-names", index,
+				      &name);
+
+	r->start = dma;
+	r->end = dma;
+	r->flags = IORESOURCE_DMA;
+	r->name = name ? name : dev->full_name;
+
+	return dma;
+}
+EXPORT_SYMBOL_GPL(of_dma_to_resource);
diff --git a/include/linux/of_dma.h b/include/linux/of_dma.h
new file mode 100644
index 0000000..575163d
--- /dev/null
+++ b/include/linux/of_dma.h
@@ -0,0 +1,49 @@
+/*
+ * OF helpers for DMA request / controller
+ *
+ * Based on of_gpio.h
+ *
+ * Copyright (C) 2012 Texas Instruments Incorporated - http://www.ti.com/
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#ifndef __LINUX_OF_DMA_H
+#define __LINUX_OF_DMA_H
+
+#include <linux/of.h>
+
+struct device_node;
+
+#ifdef CONFIG_OF_GPIO
+
+extern int of_get_dma_request(struct device_node *np, int index,
+		       struct device_node **ctrl_np);
+extern unsigned int of_dma_count(struct device_node *np);
+extern int of_dma_to_resource(struct device_node *dev, int index,
+			      struct resource *r);
+
+#else /* CONFIG_OF_DMA */
+
+static int of_get_dma_request(struct device_node *np, int index,
+			      struct device_node **ctrl_np);
+{
+	return -ENOSYS;
+}
+
+static inline unsigned int of_dma_count(struct device_node *np)
+{
+	return 0;
+}
+
+static int of_dma_to_resource(struct device_node *dev, int index,
+			      struct resource *r);
+{
+	return -ENOSYS;
+}
+
+#endif /* CONFIG_OF_DMA */
+
+#endif /* __LINUX_OF_DMA_H */
-- 
1.7.0.4